記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s00709-020-01596-9

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その他リンク： https://link.springer.com/article/10.1007/s00709-020-01596-9/fulltext.html

担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1093/pcp/pcaa142

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その他リンク： http://academic.oup.com/pcp/article-pdf/62/1/92/36718180/pcaa142.pdf

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1080/1343943x.2020.1794915

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3390/ijms21197135

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3390/ijms21176100

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/tpj.14662

PubMed

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その他リンク： https://onlinelibrary.wiley.com/doi/full-xml/10.1111/tpj.14662

担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3390/plants9010016

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1017/s0960258519000229

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/pce.13406

PubMed

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1093/pcp/pcy202

PubMed

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.plantsci.2018.10.019

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/nph.15555

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3390/plants7030061

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3390/ijms19010235

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PubMed

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その他リンク： http://orcid.org/0000-0001-7545-2771

担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/ppl.12508

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Oxford University Press (OUP)  

DOI： 10.1093/aob/mcw117

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PUBLIC LIBRARY SCIENCE  

Major intrinsic proteins (MIPs), commonly known as aquaporins, transport not only water in plants but also other substrates of physiological significance and heavy metals. In most of the higher plants, MIPs are divided into five subfamilies (PIPs, TIPs, NIPs, SIPs and XIPs). Herein, we identified 68, 42, 38 and 28 full-length MIPs, respectively in the genomes of four monocot grass plants, specifically Panicum virgatum, Setaria italica, Sorghum bicolor and Brachypodium distachyon. Phylogenetic analysis showed that the grass plants had only four MIP subfamilies including PIPs, TIPs, NIPs and SIPs without XIPs. Based on structural analysis of the homology models and comparing the primary selectivity-related motifs [two NPA regions, aromatic/arginine (ar/R) selectivity filter and Froger's positions (FPs)] of all plant MIPs that have been experimentally proven to transport non-aqua substrates, we predicted the transport profiles of all MIPs in the four grass plants and also in eight other plants. Groups of MIP subfamilies based on ar/R selectivity filter and FPs were linked to the non-aqua transport profiles. We further deciphered the substrate selectivity profiles of the MIPs in the four grass plants and compared them with their counterparts in rice, maize, soybean, poplar, cotton, Arabidopsis thaliana, Physcomitrella patens and Selaginella moellendorffii. In addition to two NPA regions, ar/R filter and FPs, certain residues, especially in loops B and C, contribute to the functional distinctiveness of MIP groups. Expression analysis of transcripts in different organs indicated that non-aqua transport was related to expression of MIPs since most of the unexpressed MIPs were not predicted to facilitate the transport of non-aqua molecules. Among all MIPs in every plant, TIP (BdTIP1;1, SiTIP1;2, SbTIP2;1 and PvTIP1;2) had the overall highest mean expression. Our study generates significant information for understanding the diversity, evolution, non-aqua transport profiles and insight into comparative transport selectivity of plant MIPs, and provides tools for the development of transgenic plants.

DOI： 10.1371/journal.pone.0157735

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：MAIK NAUKA/INTERPERIODICA/SPRINGER  

Plants grown in phosphorus-deprived solutions often exhibit disruption of water transport due to reduction in root hydraulic conductivity (Lp (r) ). To uncover the relationship between root Lp (r) and water permeability coefficient (P (f)) of plasma membrane and the role of aquaporins, we evaluated P (f) of plasma membrane and also PIP-type aquaporin gene expression in tobacco (Nicotiana tabacum L.) plant roots after seven days P-deprivation. The results showed significant reduction in sap flow rate (J (v)) and osmotic root hydraulic conductivity (L (pr-o)) in P-deprived roots. These effects were reversed 24 h after P-resupplying. Interestingly, the P (f) of root protoplasts was 57% lower in P-deprived plants compared with P-sufficient ones. The expression of NtPIP1;1 and NtPIP2;1 aquaporins did not change significantly in P-deprived plants compared with P-sufficient ones, but the copy number of NtAQP1 increased significantly in P-deprived plants. P-deprivation did not change Lp r-o significantly in antisense NtAQP1 plants. Taken together, these findings suggest that P-deprivation may play an important role in modulation of root hydraulic conductivity by affecting P (f) in transcellular pathway of water flow across roots and aquaporins. Finally, we concluded that dominant water transport pathway under P-deprivation was transcellular one.

DOI： 10.1134/S102144371601012X

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：BIOMED CENTRAL LTD  

Background: Na+ exclusion from leaf blades is one of the key mechanisms for glycophytes to cope with salinity stress. Certain class I transporters of the high-affinity K+ transporter (HKT) family have been demonstrated to mediate leaf blade-Na+ exclusion upon salinity stress via Na+-selective transport. Multiple HKT1 transporters are known to function in rice (Oryza sativa). However, the ion transport function of OsHKT1;4 and its contribution to the Na+ exclusion mechanism in rice remain to be elucidated.
Results: Here, we report results of the functional characterization of the OsHKT1; 4 transporter in rice. OsHKT1; 4 mediated robust Na+ transport in Saccharomyces cerevisiae and Xenopus laevis oocytes. Electrophysiological experiments demonstrated that OsHKT1; 4 shows strong Na+ selectivity among cations tested, including Li+, Na+, K+, Rb+, Cs+, and NH4+, in oocytes. A chimeric protein, EGFP-OsHKT1;4, was found to be functional in oocytes and targeted to the plasma membrane of rice protoplasts. The level of OsHKT1; 4 transcripts was prominent in leaf sheaths throughout the growth stages. Unexpectedly however, we demonstrate here accumulation of OsHKT1;4 transcripts in the stem including internode II and peduncle in the reproductive growth stage. Moreover, phenotypic analysis of OsHKT1;4 RNAi plants in the vegetative growth stage revealed no profound influence on the growth and ion accumulation in comparison with WT plants upon salinity stress. However, imposition of salinity stress on the RNAi plants in the reproductive growth stage caused significant Na+ overaccumulation in aerial organs, in particular, leaf blades and sheaths. In addition, Na-22(+) tracer experiments using peduncles of RNAi and WT plants suggested xylem Na+ unloading by OsHKT1;4.
Conclusions: Taken together, our results indicate a newly recognized function of OsHKT1;4 in Na+ exclusion in stems together with leaf sheaths, thus excluding Na+ from leaf blades of a japonica rice cultivar in the reproductive growth stage, but the contribution is low when the plants are in the vegetative growth stage.

DOI： 10.1186/s12870-016-0709-4

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER JAPAN KK  

HKT transporters are Na+-permeable membrane proteins, which mediate Na+ and K+ homeostasis in K+-depleted and saline environments in plants. Class II HKT transporters, a distinct subgroup found predominantly in monocots, are known to mediate Na+-K+ co-transport in principle. Here we report features of ion transport functions of No-OsHKT2;2/1, a class II transporter identified in a salt tolerant landrace of indica rice, Nona Bokra. We profiled No-OsHKT2;2/1 expression in organs of Nona Bokra plants with or without salinity stress. Dominant accumulation of the No-OsHKT2;2/1 transcript in K+-starved roots of Nona Bokra plants largely disappeared in response to 50 mM NaCl. We found that No-OsHKT2;2/1 expressed in the high-affinity K+ uptake deficient mutant of Saccharomyces cerevisiae and Xenopus laevis oocytes shows robust K+ selectivity even in the presence of a large amount of NaCl as reported previously. However, No-OsHKT2;2/1-expressing yeast cells exhibited Na+ hypersensitive growth under various concentrations of K+ and Na+ as the cells expressing Po-OsHKT2;2, a similar class II transporter from another salt tolerant indica rice Pokkali, when compared with the growth of cells harboring empty vector or cells expressing OsHKT2;4. The OsHKT2;4 protein expressed in Xenopus oocytes showed strong K+ selectivity in the presence of 50 mM NaCl in comparison with No-OsHKT2;2/1 and Po-OsHKT2;2. Together with apparent plasma membrane-localization of No-OsHKT2;2/1, these results point to possibilities that No-OsHKT2;2/1 could mediate destructive Na+ influx over K+ uptake in Nona Bokra plants upon salinity stress, and that a predominant physiological function of No-OsHKT2;2/1 might be the acquisition of Na+ and K+ in K+-limited environments.

DOI： 10.1007/s10265-015-0764-1

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：FRONTIERS MEDIA SA  

Salinity is a critical environmental factor that adversely affects crop productivity. Halophytes have evolved various mechanisms to adapt to saline environments. Salicornia europaea L. is one of the most salt tolerant plant species. It does not have special salt-secreting structures like a salt gland or salt bladder, and is therefore a good model for studying the common mechanisms underlying plant salt tolerance. To identify candidate genes encoding key proteins in the mediation of salt tolerance in S. europaea, we performed a functional screen of a cDNA library in yeast. The library was screened for genes that allowed the yeast to grow in the presence of 1.3 M NaCl. We obtained three full-length S. europaea genes that confer salt tolerance. The genes are predicted to encode (1) a novel protein highly homologous to thaumatin-like proteins, (2) a novel coiled-coil protein of unknown function, and (3) a novel short peptide of 32 residues. Exogenous application of a synthetic peptide corresponding to the 32 residues improved salt tolerance of Arabidopsis. The approach described in this report provides a rapid assay system for large-scale screening of S. europaea genes involved in salt stress tolerance and supports the identification of genes responsible for such mechanisms. These genes may be useful candidates for improving crop salt tolerance by genetic transformation.

DOI： 10.3389/fpls.2015.00920

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

Tonoplast intrinsic proteins (TIPs) are involved in the transport and storage of water, and control intracellular osmotic pressure by transporting material related to the water potential of cells. In the present study, we focused on HvTIP3;1 during the periods of seed development and desiccation in barley. HvTIP3;1 was specifically expressed in seeds. An immunochemical analysis showed that HvTIP3;1 strongly accumulated in the aleurone layers and outer layers of barley seeds. The water transport activities of HvTIP3;1 and HvTIP1;2, which also accumulated in seeds, were measured in the heterologous expression system of Xenopus oocytes. When they were expressed individually, HvTIP1;2 transported water, whereas HvTIP3;1 did not. However, HvTIP3;1 exhibited water transport activity when co-expressed with HvTIP1;2 in oocytes, and this activity was higher than when HvTIP1;2 was expressed alone. This is the first report to demonstrate that the water permeability of a TIP aquaporin was activated when co-expressed with another TIP. The split-yellow fluorescent protein (YFP) system in onion cells revealed that HvTIP3;1 interacted with HvTIP1;2 to form a heterotetramer in plants. These results suggest that HvTIP3;1 functions as an active water channel to regulate water movement through tissues during the periods of seed development and desiccation.

DOI： 10.1093/pcp/pcv104

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

Salinity stress significantly reduces the root hydraulic conductivity (Lp(r)) of several plant species including barley (Hordeum vulgare). Here we characterized changes in the Lp(r) of barley plants in response to salinity/osmotic stress in detail using a pressure chamber. Salt-tolerant and intermediate barley cultivars, K305 and Haruna-nijyo, but not a salt-sensitive cultivar, I743, exhibited characteristic time-dependent Lp(r) changes induced by 100 mM NaCl. An identical response was evoked by isotonic sorbitol, indicating that this phenomenon was triggered by osmotic imbalances. Further examination of this mechanism using barley cv. Haruna-nijyo plants in combination with the use of various inhibitors suggested that various cellular processes such as protein phosphorylation/dephosphorylation and membrane internalization appear to be involved. Interestingly, the three above-mentioned barley cultivars did not exhibit a remarkable difference in root cell sap osmolality under hypertonic conditions, in contrast to the case of Lp(r). The possible biological significance of the regulation of Lp(r) in barley plants upon salinity/osmotic stress is discussed.

DOI： 10.1093/pcp/pcv013

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER JAPAN KK  

Previous reports indicate that salt stress reduces the root hydraulic conductance and the expression of plasmamembrane-type aquaporins (PIPs). As a molecular mechanism for this phenomenon, the present study found evidence that the osmotic component, but probably not an ion-specific component, decreases PIP transcripts. Eight of ten PIP transcripts were reduced to less than half by 360 mM mannitol treatment for 12 h in comparison with control samples. A large decrease of HvPIP2; 1 protein was also recorded. This reduction of both transcripts and proteins of HvPIP2s should be physiologically effective for preventing or reducing dehydration at an initial phase of severe salt/osmotic stress. Root cell sap osmolality increased from 278 to 372 mOsm 24 h after 360 mM mannitol treatment. These steps can secure survival and growth recovery with water reabsorption in barley. Our data also suggest that H2O2 seems not to be the main cause of osmotic stress-induced transcriptional down-regulation within the concentrations (20-500 mu M) and time periods (24 h) examined, although H2O2 was previously proposed to be involved in the mechanisms of salinity/osmotic tolerance.

DOI： 10.1007/s10265-014-0662-y

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記述言語：中国語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Science Press  

The plant plasma membrane aquaporin (plasma membrane intrinsic proteins, PIPs) is a kind of membrane intrinsic proteins which has high selectivity and water transport. They play important roles in many physiological activities in plant growth and development. In this study, seedlings of barley variety 'Haruna-nijo' were treated with chilling stress. Expression of water channel protein PIPs of root in two processes which were stress period (4℃, 48 h) and recovery period (16℃, 48 h) were analyzed with quantitative real-time reverse transcriptase PCR (qRT-PCR). And root hydraulic conductivity (Lpr), root length and seedling height were analyzed at the same time. The results showed that: after 4℃ and 48 h stress, the growth of the barley seedlings was significantly inhibited, but root growth was no significant changed
after 16℃, 48 h recovery, shoot height of stressed-seedling caught up that of control seedlings and root growth did not change significantly
root hydraulic conductivity decreased in the period of chilling stress and increased rapidly in recovery period but there were no significant difference. The results of qRT-PCR showed: the highest expression were HvPIP1
2 and HvPIP1
3, the lowest expression were HvPIP1
1 and HvPIP2
3. Compared with the control group, HvPIPs expression were decreased in all after cold treatment, in which HvPIP1
2, HvPIP1
3, HvPIP1
4, HvPIP1
5, HvPIP2
1, HvPIP2
2 were down-regulated significantly. In recovery period, most of HvPIPs expression were increased, espeacally HvPIP1
1, HvPIP1
2, HvPIP1
5, HvPIP2
3 were up-regulated significantly, but HvPIP1
4, HvPIP2
5 were down-regulated. This study found that HvPIPs expressions of barley root were down-regulated overall in chilling stress and in recovery growth most HvPIPs were up-regulated. Combined with changes of root hydraulic conductivity and plant growth, the role of barley HvPIPs in chilling resistance reaction speculated that HvPIPs effected water absorption were different in different stages.

DOI： 10.13592/j.cnki.ppj.2014.0242

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

CO2 permeability of plasma membrane intrinsic protein 2 (PIP2) aquaporins of Hordeum vulgare L. was investigated. Five PIP2 members were heterologously expressed in Xenopus laevis oocytes. CO2 permeability was determined by decrease of cytosolic pH in CO2-enriched buffer using a hydrogen ion-selective microelectrode. HvPIP2; 1, HvPIP2; 2, HvPIP2; 3 and HvPIP2; 5 facilitated CO2 transport across the oocyte cell membrane. However, HvPIP2; 4 that is highly homologous to HvPIP2; 3 did not. The isoleucine residue at position 254 of HvPIP2; 3 was conserved in PIP2 aquaporins of barley, except HvPIP2; 4, which possesses methionine instead. CO2 permeability was lost by the substitution of the Ile254 of HvPIP2; 3 by methionine, while water permeability was not affected. These results suggest that PIP2 aquaporins are permeable to CO2. and the conserved isoleucine at the end of the E-loop is crucial for CO2 selectivity.

DOI： 10.1093/pcp/pcu003

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPANESE SOC PLANT CELL & MOLECULAR BIOLOGY  

Mercury-sensitive water transport activities were detected in seven NIP (Nodulin 26-like intrinsic protein) type aquaporins among eleven NIPs examined. Amino acid substitutions in rice OsNIP3;3 revealed that mercury-sensitivity depended on a histidine (but not on a cysteine) in apoplastic loop C in plant NIP aquaporins, although the cysteine is involved in the mercury-sensitivity of animal aquaporins. Rice OsNIP3;3 was also first identified as a unique aquaporin facilitating all water, hydrogen peroxide and arsenite transports. In rice OsNIP3;2, hydrogen peroxide and arsenite transport activities were detected, but water transport was not. Barley HvNIP1;2- or rice OsNIP2;1-expressing yeast cells showed the arsenite transport activity but not the H2O2 transport activity. The present work revealed novel molecular mechanisms of water and other low molecular weight compounds transport/selection in barley and rice NIP aquaporins, including the histidine-related mercury-sensitivity in the water transport of aquaporins.

DOI： 10.5511/plantbiotechnology.14.0421a

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER JAPAN KK  

We investigated the photosynthetic capacity and plant growth of tobacco plants overexpressing ice plant (Mesembryanthemum crystallinum L.) aquaporin McMIPB under (1) a well-watered growth condition, (2) a well-watered and temporal higher vapor pressure deficit (VPD) condition, and (3) a soil water deficit growth condition to investigate the effect of McMIPB on photosynthetic responses under moderate soil and atmospheric humidity and water deficit conditions. Transgenic plants showed a significantly higher photosynthesis rate (by 48 %), higher mesophyll conductance (by 52 %), and enhanced growth under the well-watered growth condition than those of control plants. Decreases in the photosynthesis rate and stomatal conductance from ambient to higher VPD were slightly higher in transgenic plants than those in control plants. When plants were grown under the soil water deficit condition, decreases in the photosynthesis rate and stomatal conductance were less significant in transgenic plants than those in control plants. McMIPB is likely to work as a CO2 transporter, as well as control the regulation of stomata to water deficits.

DOI： 10.1007/s10265-013-0548-4

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：HUMANA PRESS INC  

Aluminum (Al) stress represses mitochondrial respiration and produces reactive oxygen species (ROS) in plants. Mitochondrial alternative oxidase (AOX) uncouples respiration from mitochondrial ATP production and may improve plant performance under Al stress by preventing excess accumulation of ROS. We tested respiratory changes and ROS production in isolated mitochondria and whole cell of tobacco (SL, ALT 301) under Al stress. Higher capacities of AOX pathways relative to cytochrome pathways were observed in both isolated mitochondria and whole cells of ALT301 under Al stress. AOX1 when studied showed higher AOX1 expression in ALT 301 than SL cells under stress. In order to study the function of tobacco AOX gene under Al stress, we produced transformed tobacco cell lines by introducing NtAOX1 expressed under the control of the cauliflower mosaic virus (CaMV) 35 S promoter in sensitive (SL) Nicotiana tabacum L. cell lines. The enhancement of endogenous AOX1 expression and AOX protein with or without Al stress was in the order of transformed tobacco cell lines > ALT301 > wild type (SL). A decreased respiratory inhibition and reduced ROS production with a better growth capability were the significant features that characterized AOX1 transformed cell lines under Al stress. These results demonstrated that AOX plays a critical role in Al stress tolerance with an enhanced respiratory capacity, reducing mitochondrial oxidative stress burden and improving the growth capability in tobacco cells.

DOI： 10.1007/s12033-012-9595-7

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Background information: Cyanobacteria possess Aquaporin-Z (AqpZ) membrane channels which have been suggested to mediate the water efflux underlying osmostress-inducible gene expression and to be essential for glucose metabolism under photomixotrophic growth. However, preliminary observations suggest that the biophy-sical properties of transport and physiological meaning of AqpZ in such photosynthetic microorganisms are not yet completely assessed. Results: In this study, we used Xenopus laevis oocyte and proteoliposome systems to directly demonstrate the water permeability of the cyanobacterium Synechococcus sp. PCC7942 aquaporin, SsAqpZ. By an in vitro assay of intracellular acidification in yeast cells, SsAqpZ was found to transport also CO2. Consistent with this result, during the entire exponential phase of growth, Synechococcus SsAqpZ-null-mutant cells grew slower than the corresponding wild-type cells. This phenotype was stronger with higher levels of extracellular CO2. In line with the conversion of CO2 gas into HCO3- ions under alkaline conditions, the impairment in growth of the SsAqpZ-null strain was weaker in more alkaline culture medium. Conclusions: Cyanobacterial SsAqpZ may exert a pleiotropic function in addition to the already reported roles in macronutrient homeostasis and osmotic-stress response as it appears to constitute an important pathway in CO2 uptake, a fundamental step in photosynthesis. © 2013 Soçiété Française des Microscopies and Soçiété de Biologie Cellulaire de France.

DOI： 10.1111/boc.201200057

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER  

OsPIP1;1 is one of the most abundant aquaporins in rice leaves and roots and is highly responsible to environmental stresses. However, its biochemical and physiological functions are still largely unknown. The oocyte assay data showed OsPIP1;1 had lower water channel activity in contrast to OsPIP2;1. EGFP and immunoelectron microscopy studies revealed OsPIP1;1 was predominantly localized in not only plasma membrane but also in some ER-like intracellular compartments in the cells. OsPIP1;1 exhibited low water channel activity in Xenopus oocytes but coexpression of OsPIP2;1 significantly enhanced its water permeability. Stop-flow assay indicated that 10His-OsPIP1;1-reconstituted proteoliposomes had significantly higher water permeability than the control liposomes. Overexpression of OsPIP1;1 greatly altered many physiological features of transgenic plants in a dosage-dependent manner. Moderate expression of OsPIP1;1 increased rice seed yield, salt resistance, root hydraulic conductivity, and seed germination rate. This work suggests OsPIP1;1 functions as an active water channel and plays important physiological roles. Published by Elsevier Masson SAS.

DOI： 10.1016/j.plaphy.2012.11.018

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記述言語：英語   出版者・発行元：SPRINGER  

Elevated Na+ levels in agricultural lands are increasingly becoming a serious threat to the world agriculture. Plants suffer osmotic and ionic stress under high salinity due to the salts accumulated at the outside of roots and those accumulated at the inside of the plant cells, respectively. Mechanisms of salinity tolerance in plants have been extensively studied and in the recent years these studies focus on the function of key enzymes and plant morphological traits. Here, we provide an updated overview of salt tolerant mechanisms in glycophytes with a particular interest in rice (Oryza sativa) plants. Protective mechanisms that prevent water loss due to the increased osmotic pressure, the development of Na+ toxicity on essential cellular metabolisms, and the movement of ions via the apoplastic pathway (i.e. apoplastic barriers) are described here in detail.

DOI： 10.1186/1939-8433-5-11

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

The effects of low air humidity and low root temperature (LRT) on water uptake, growth and aquaporin gene expression were investigated in rice plants. The daily transpiration of the plants grown at low humidity was 1.5- to 2-fold higher than that at high humidity. LRT at 13 degrees C reduced transpiration, and the extent was larger at lower humidity. LRT also reduced total dry matter production and leaf area expansion, and the extent was again larger at lower humidity. These observations suggest that the suppression of plant growth by LRT is associated with water stress due to decreased water uptake ability of the root. On the other hand, the net assimilation rate was not affected by low humidity and LRT, and water use efficiency was larger for LRT. We found that low humidity induced coordinated up-regulation of many PIP and TIP aquaporin genes in both the leaves and the roots. Expression levels of two root-specific aquaporin genes, OsPIP2;4 and OsPIP2;5, were increased significantly after 6 and 13 d of LRT exposure. Taken together, we discuss the possibility that aquaporins are part of an integrated response of this crop to low air humidity and LRT.

DOI： 10.1093/pcp/pcs087

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER TOKYO  

Although aquaporins have been known to transport hydrogen peroxide (H(2)O(2)) across cell membranes, the H(2)O(2)-regulated expression patterns and the permeability of every family member of the plasma membrane intrinsic protein (PIP) toward H(2)O(2) have not been determined. This study investigates the H(2)O(2)-regulated expression levels of all plasma membrane aquaporins of Arabidopsis thaliana (AtPIPs), and determines the permeability of every AtPIP for H(2)O(2) in yeast. Hydrogen peroxide treatment of Arabidopsis down-regulated the expression of AtPIP2 subfamily in roots but not in leaves, whereas the expression of AtPIP1 subfamily was not affected by H(2)O(2) treatment. The growth and survival of yeast cells that expressed AtPIP2;2, AtPIP2;4, AtPIP2;5, or AtPIP2;7 was reduced in the presence of H(2)O(2), while the growth of yeast cells expressing any other AtPIP family member was not affected by H(2)O(2). These results show that only certain isoforms of AtPIPs whose expression is regulated by H(2)O(2) treatment are permeable for H(2)O(2) in yeast cells, and suggest that the integrated regulation of aquaporin expression by H(2)O(2) and the capacity of individual aquaporin to transport H(2)O(2) are important for plant response to H(2)O(2).

DOI： 10.1007/s10265-011-0413-2

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Water homeostasis is crucial to the growth and survival of plants. Plasma membrane intrinsic proteins (PIPs) have been shown to be primary channels mediating water uptake in plant cells. We characterized a novel PIP2 gene, HvPIP2
8 in barley (Hordeum vulgare). HvPIP2
8 shared 72-76% identity with other HvPIP2s and 74% identity with rice OsPIP2
8. The gene was expressed in all organs including the shoots, roots and pistil at a similar level. When HvPIP2
8 was transiently expressed in onion epidermal cells, it was localized to the plasma membrane. HvPIP2
8 showed transport activity for water in Xenopus oocytes, however its interaction with HvPIP1
2 was not observed. These results suggest that HvPIP2
8 plays a role in water homeostasis although further functional analysis is required in future. © 2012 Landes Bioscience.

DOI： 10.4161/psb.22294

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：KOREAN SOC HORTICULTURAL SCIENCE  

Effects of nitrogen, phosphorus, and potassium deficiencies on water transport properties in figleaf gourd plants were studied. Plants were treated for different period of deficiency and physiological parameters such as stomatal conductance, photosynthesis and transpiration were measured. Cell and root pressure probes were utilized to measure turgor and root pressures, half-times of water exchange and hydraulic conductivities to analyze water transport properties. When plants were grown in nitrogen or phosphorus deficient nutrient solutions, they became insensitive to mercury, suggesting that aquaporin was closed resulting in reduced hydraulic conductivity. Inclusion of tungstate, however, restored the sensitivity of cells to mercury, indicating the importance of internal nutrient concentration, not the incoming nutrient supply. The hydrostatic hydraulic conductivity of roots grown in nitrogen deficient solution, representing apoplastic pathway of water transport, was reduced but this reduction was dramatically recovered by the application of tungstate, indicating the importance of nutrient availability from storage pools in relation to water status of plants.

DOI： 10.1007/s13580-011-0046-3

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC PLANT BIOLOGISTS  

Members of class II of the HKT transporters, which have thus far only been isolated from grasses, were found to mediate Na+-K+ cotransport and at high Na+ concentrations preferred Na+-selective transport, depending on the ionic conditions. But the physiological functions of this K+-transporting class II of HKT transporters remain unknown in plants, with the exception of the unique class II Na+ transporter OsHKT2;1. The genetically tractable rice (Oryza sativa; background Nipponbare) possesses two predicted K+-transporting class II HKT transporter genes, OsHKT2;3 and OsHKT2;4. In this study, we have characterized the ion selectivity of the class II rice HKT transporter OsHKT2;4 in yeast and Xenopus laevis oocytes. OsHKT2;4 rescued the growth defect of a K+ uptake-deficient yeast mutant. Green fluorescent protein-OsHKT2;4 is targeted to the plasma membrane in transgenic plant cells. OsHKT2;4-expressing oocytes exhibited strong K+ permeability. Interestingly, however, K+ influx in OsHKT2;4-expressing oocytes did not require stimulation by extracellular Na+, in contrast to other class II HKT transporters. Furthermore, OsHKT2;4-mediated currents exhibited permeabilities to both Mg2+ and Ca2+ in the absence of competing K+ ions. Comparative analyses of Ca2+ and Mg2+ permeabilities in several HKT transporters, including Arabidopsis thaliana HKT1;1 (AtHKT1;1), Triticum aestivum HKT2;1 (TaHKT2;1), OsHKT2;1, OsHKT2;2, and OsHKT2;4, revealed that only OsHKT2;4 and to a lesser degree TaHKT2;1 mediate Mg2+ transport. Interestingly, cation competition analyses demonstrate that the selectivity of both of these class II HKT transporters for K+ is dominant over divalent cations, suggesting that Mg2+ and Ca2+ transport via OsHKT2;4 may be small and would depend on competing K+ concentrations in plants.

DOI： 10.1104/pp.110.168047

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

Water homeostasis is crucial to the growth and survival of plants under water-related stress. Plasma membrane intrinsic proteins (PIPs) have been shown to be primary channels mediating water uptake in plant cells. Here we report the water transport activity and mechanisms for the regulation of barley (Hordeum vulgare) PIP aquaporins. HvPIP2 but not HvPIP1 channels were found to show robust water transport activity when expressed alone in Xenopus laevis oocytes. However, the co-expression of HvPIP1 with HvPIP2 in oocytes resulted in significant increases in activity compared with the expression of HvPIP2 alone, suggesting the participation of HvPIP1 in water transport together with HvPIP2 presumably through heteromerization. Severe salinity stress (200 mM NaCl) significantly reduced root hydraulic conductivity (Lp(r)) and the accumulation of six of 10 HvPIP mRNAs. However, under relatively mild stress (100 mM NaCl), only a moderate reduction in Lp(r) with no significant difference in HvPIP mRNA levels was observed. Sorbitol-mediated osmotic stress equivalent to 100 and 200 mM NaCl induced nearly identical Lp(r) reductions in barley roots. Furthermore, the water transport activity in intact barley roots was suggested to require phosphorylation that is sensitive to a kinase inhibitor, staurosporine. HvPIP2s also showed water efflux activity in Xenopus oocytes, suggesting a potential ability to mediate water loss from cells under hypertonic conditions. Water transport via HvPIP aquaporins and the significance of reductions of Lp(r) in barley plants during salinity stress are discussed.

DOI： 10.1093/pcp/pcr027

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SOC BIOSCIENCE BIOENGINEERING JAPAN  

Potassium ion (K(+)) plays vital roles in many aspects of cellular homeostasis including competing with sodium ion (Na(+)) during potassium starvation and salt stress. Therefore, one way to engineer plant cells with improved salt tolerance is to enhance K(+) uptake activity of the cells, while keeping Na(+) out during salt stress. Here, in search for Na(+)-insensitive transporter for this purpose, bacterial expression system was used to characterize two K(+) transporters, OsHAK2 and OsHAK5, isolated from rice (Oryza sativa cv. Nipponbare). The two OsHAK transporters are members of a KT/HAK/KUP transporter family, which is one of the major K(+) transporter families in bacteria, fungi and plants. When expressed in an Escherichia cola K(+) transport mutant strain LB2003, both OsHAK transporters rescued the growth defect in K(+)-limiting conditions by significantly increasing the K(+) content of the cells. Under the condition with a large amount of extracellular Na(+), we found that OsHAK5 functions as a Na(+)-insensitive K(+) transporter, while OsHAK2 is sensitive to extracellular Na(+) and exhibits higher Na(+) over K(+) transport activities. Moreover, constitutive expression of OsHAK5 in cultured-tobacco BY2 (Nicotiana tabacum cv. Bright Yellow 2) cells enhanced the accumulation of K(+) but not Na(+) in the cells during salt stress and conferred increased salt tolerance to the cells. Transient expression experiment indicated that OsHAK5 is localized to the plant plasma membrane. These results suggest that the plasma-membrane localized Na(+) insensitive K(+) transporters, similar to OsHAK5 identified here, could be used as a tool to enhance salt tolerance in plant cells. (C) 2010, The Society for Biotechnology, japan. All rights reserved.

DOI： 10.1016/j.jbiosc.2010.10.014

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER GMBH, URBAN & FISCHER VERLAG  

Natural rubber is synthesized in laticifers in the inner liber of the rubber tree (Hevea brasiliensis). Upon bark tapping, the latex is expelled due to fiber turgor pressure. The mature laticifers are devoid of plasmodesmata; therefore a corresponding decrease-in the total latex solid content is likely to occur due to water influx inside the laticifers. Auxins and ethylene used as efficient yield stimulants in mature untapped rubber trees, but, bark treatments with abscisic acid (ABA) and salicylic acid (SA) could also induce a transient increase latex yield. We recently reported that there are three aquaporin genes, HbPIP2;1, HbT1P1;1 and HbPIP1;1, that are regulated differentially after ethylene bark treatment. HbPIP2:1 was up-regulated in both the laticifers and the inner liber tissues, whereas HbT1P1:1 was up-regulated in the latex cells, but very markedly down-regulated in the inner liber tissues. Conversely, HbPIP1:1 was down-regulated in both tissues. In the present study, HbPIP2;1 and HbT1P1:1 showed a similar expression in response to auxin, ABA and SA, as seen in ethylene stimulation, while HbPIP1;1 was slightly regulated by auxin, but neither by ABA nor SA. The analysis of the HbPIP1:1 promoter region indicated the presence of only ethylene and auxin responsive elements. In addition, the poor efficiency of this HbPIP1;1 in increasing plasmalemma water conductance was confirmed in Xenopus oocytes. Thus, an increase in latex yield in response to all of these hormones was proposed to be the major function of aquaporins, HbPIP2:1 and HbTIP1;1. This study emphasized that the circulation of water between the laticifers and their surrounding tissues that result in latex dilution, as well as the probable maintenance of the liber tissues turgor pressure, favor the prolongation of latex flow. (C) 2010 Elsevier GmbH. All rights reserved.

DOI： 10.1016/j.jplph.2010.06.009

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER  

In one of the most important crops, barley (Hordeum vulgare L), gene expression and physiological roles of most major intrinsic proteins (MIPs) remained to be elucidated. Here we studied expression of five tonoplast intrinsic protein isoforms (HvTIP1;2, HvTIP2:1, HvTIP2;2,HvTIP2;3 and HvTIP4:1), a NOD26-like intrinsic protein (HvNIP2;1) and a plasma membrane intrinsic protein (HvPIP2;1) by using the quantitative real-time RT-PCR. Five-day-old seedlings were exposed to abiotic stresses (salt, heavy metals and nutrient deficiency), abscisic acid (ABA) and gibberellic acid (GA) for 24 h. Treatment with 100 mM NaCl, 0.1 mM ABA and 1 mM GA differentially regulated gene expression in roots and shoots. Nitrogen and prolonged P-deficiency downregulated expression of most MIP genes in roots. Intriguingly, gene expression was restored to the values in the control three days after nutrient supply was resumed. Heavy metals (0.2 mM each of Cd, Cu, Zn and Cr) downregulated the transcript levels by 60-80% in roots, whereas 0.2 mM Hg upregulated expressions of most genes in roots. This was accompanied by a 45% decrease in the rate of transpiration. In order to study the physiological role of the MIPs, cDNA of three genes (HvTIP2:1, HvTIP2:3 and HvNIP2;1) have been cloned and heterologous expression was performed in Xenopus laevis oocytes. Osmotic water permeability was determined by a swelling assay. However, no water uptake activity was observed for the three proteins. Hence, the possible physiological role of the proteins is discussed. (C) 2010 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

DOI： 10.1016/j.crvi.2010.11.005

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY-BLACKWELL  

Barley varieties, K305 and I743, which are sodium chloride (NaCl) tolerant and sensitive respectively, were hydroponically grown to determine the short-term effects of NaCl on the cell water relations in roots using a cell pressure probe, and on the transcript levels of 10 barley PIP aquaporin genes (HvPIPs) in roots. Stomatal conductance, as an indicator of sensitivity to NaCl, was decreased to less than half values of control upon exposure to 100 mmol L-1 NaCl for 24 h in I743 whereas tolerant variety, K305, was able to maintain original conductance. Osmotic half-times of water exchange in cortical cells allowed for a clear distinction between the two varieties up to 200 mmol L-1 NaCl. With treatment duration of up to 12 h with 100 mmol L-1 NaCl, the elastic modulus was reduced in I743 but increased in K305. Hydrostatic half-times of water exchange in K305 increased rapidly, whereas this value remained unchanged in I743. Application of abscisic acid (ABA) after 1 h NaCl treatment restored the hydraulic conductivity of cells (Lp) in K305 but not in I743 whereas the opposite results were obtained when mercury chloride (HgCl2) was applied, verifying the contrasting gating response of aquaporins in two varieties. Reduced expression of HvPIPs was consistent with the reduction of hydraulic conductivity of both varieties after 24 h NaCl, but without any significant differences between them, indicating the importance of the activities of existing aquaporins rather than de novo synthesis to cope with short-term effects of salt stress.

DOI： 10.1080/00380768.2010.541870

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s10265-009-0272-2

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1104/pp.109.145722

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3390/s100706290

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出版者・発行元：日本植物生理学会  

塩ストレスは作物の成長・収量を減少させる代表的な非生物的ストレスの一種である。塩ストレスにさらされたオオムギの根の水輸送特性及び制御機構を解明するため、我々はプレッシャーチャンバー法を用いた研究を進めており、これまでに塩ストレスによって引き起こされる水輸送活性の変化は浸透圧刺激を受容することによるものであることを明らかにした。また、耐塩性品種ではストレス開始後1時間で水輸送活性は急速に低下し、4時間で一過的な回復が起こるが、脱リン酸化阻害剤であるokadaic acid (OA) 処理によってストレス開始後1時間で起こる水輸送活性の急激な低下は抑制されたものの、未処理と比較した場合にその抑制程度は不十分なものであった。一方、エンドサイトーシス阻害剤のwartmannin（WM）処理では十分に抑制された。さらに、エキソサイトーシス阻害剤のbrefeldin A (BFA) 処理によってストレス開始4時間で起こる水輸送活性の一過的回復が抑制された。これらのことは、膜タンパク質のリン酸化、およびエンドサイトーシスを伴ったリサイクリングが関与している可能性を示唆するものである。現在免疫学的手法による解析も進めており、これらについても報告する。<br>この研究は生研センター基礎研究推進事業の支援を受けて行った。

DOI： 10.14841/jspp.2010.0.0034.0

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC PLANT BIOLOGISTS  

Natural rubber is synthesized in specialized articulated cells (laticifers) located in the inner liber of Hevea brasiliensis. Upon bark tapping, the laticifer cytoplasm (latex) is expelled due to liber tissue turgor pressure. In mature virgin (untapped) trees, short-term kinetic studies confirmed that ethylene, the rubber yield stimulant used worldwide, increased latex yield, with a concomitant decrease in latex total solid content, probably through water influx in the laticifers. As the mature laticifers are devoid of plasmodesmata, the rapid water exchanges with surrounding liber cells probably occur via the aquaporin pathway. Two full-length aquaporin cDNAs (HbPIP2;1 and HbTIP1;1, for plasma membrane intrinsic protein and tonoplast intrinsic protein, respectively) were cloned and characterized. The higher efficiency of HbPIP2;1 than HbTIP1;1 in increasing plasmalemma water conductance was verified in Xenopus laevis oocytes. HbPIP2;1 was insensitive to HgCl(2). In situ hybridization demonstrated that HbPIP2;1 was expressed in all liber tissues in the young stem, including the laticifers. HbPIP2;1 was up-regulated in both liber tissues and laticifers, whereas HbTIP1;1 was down-regulated in liber tissues but up-regulated in laticifers in response to bark Ethrel treatment. Ethylene-induced HbPIP2;1 up-regulation was confirmed by western-blot analysis. The promoter sequences of both genes were cloned and found to harbor, among many others, ethylene-responsive and other chemical-responsive (auxin, copper, and sulfur) elements known to increase latex yield. Increase in latex yield in response to ethylene was emphasized to be linked with water circulation between the laticifers and their surrounding tissues as well as with the probable maintenance of liber tissue turgor, which together favor prolongation of latex flow.

DOI： 10.1104/pp.109.140228

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出版者・発行元：日本植物生理学会  

PIP型アクアポリン(Plasma Membrane Intrinsic Protein)は、水の透過孔を形成する細胞膜タンパク質であり、水輸送に重要な役割を果たしている。塩ストレス下におけるオオムギ(Hordeum Vulgare cv. Haruna-nijo)の根の水輸送特性を分子生物学的観点から解析した。発芽後4日齢のオオムギの根に、NaClを一定時間処理し定量的RT-PCR解析を行った結果、200 mMの塩処理によって10種中6種のHvPIP mRNAの蓄積量が顕著に減少した。プレッシャーチャンバー法によりオオムギ根の水透過性を性格付けした結果、200 mM NaClの塩処理によって根の水透過性が著しく減退する事が判明した。各種生物活性阻害剤を併用した解析から、オオムギ根の水透過性は、少なくともリン酸化によって制御されている事が強く示唆された。アフリカツメガエルの卵母細胞を用いて各HvPIPの水輸送特性を解析した結果、単独では水輸送活性を示さないHvPIP1型アクアポリンは、単独で高い水輸送活性を示すHvPIP2型と共発現する事により、HvPIP2型の水輸送活性を強める事が判明した。これらの結果をもとに、オオムギの根におけるHvPIPを介した水輸送機構、及び塩ストレス時の根における水輸送活性制御機構について議論する。（生研センター基礎研究推進事業の支援により実施）

DOI： 10.14841/jspp.2009.0.s0029.0

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

We suggested previously that temperature-dependent tulip (Tulipa gesneriana) petal movement that is concomitant with water transport is regulated by reversible phosphorylation of an unidentified plasma membrane intrinsic protein (PIP). In this study, four full-length cDNAs of PIPs from tulip petals were identified and cloned. Two PIPs, namely TgPIP1;1 and TgPIP1;2, are members of the PIP1 subfamily, and the remaining two PIPs, namely TgPIP2;1 and TgPIP2;2, belong to the PIP2 subfamily of aquaporins and were named according to the nomenclature of PIP genes in plants. Of these four homologs, only TgPIP2;2 displayed significant water channel activity in the heterologous expression assay using Xenopus laevis oocytes. The water channel activity of this functional isoform was abolished by mercury and was affected by inhibitors of protein kinase and protein phosphatase. Using a site-directed mutagenesis approach to substitute several serine residues with alanine, and assessing water channel activity using the methylotrophic yeast Pichia pastoris expression assay, we showed that Ser35, Ser116 and Ser274 are the putative phosphorylation sites of TgPIP2;2. Real-time reverse transcriptionPCR analysis revealed that the transcript levels of TgPIP1;1 and TgPIP1;2 in tulip petals, stems, leaves, bulbs and roots are very low when compared with those of TgPIP2;1 and TgPIP2;2. The transcript level of TgPIP2;1 is negligible in roots, and TgPIP2;2 is ubiquitously expressed in all organs with significant transcript levels. From the data reported herein, we suggest that TgPIP2;2 might be modulated by phosphorylation and dephosphorylation for regulating water channel activity, and may play a role in transcellular water transport in all tulip organs.

DOI： 10.1093/pcp/pcn095

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER  

We identified barley aquaporins and demonstrated that one, HvPIP2;1, transports water and CO(2). Regarding water homeostasis in plants, regulations of aquaporin expression were observed in many plants under several environmental stresses. Under salt stress, a number of plasma membrane-type aquaporins were down-regulated, which can prevent continuous dehydration resulting in cell death. The leaves of transgenic rice plants that expressed the largest amount of HvPIP2;1 showed a 40% increase in internal CO(2) conductance compared with leaves of wild-type rice plants. The rate of CO(2) assimilation also increased in the transgenic plants. The goal of our plant aquaporin research is to determine the key aquaporin species responsible for water and CO(2) transport, and to improve plant water relations, stress tolerance, CO(2) uptake or assimilation, and plant productivity via molecular breeding of aquaporins.

DOI： 10.1007/s00424-007-0434-9

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

Plasma membrane intrinsic proteins (PIPs), a type of aquaporins, mediate water transport in many plant species. In this study, we investigated the relationship between the functions of PIP-type water channels and water relations of tobacco plants (Nicotiana tabacum cv. Samsun) under drought stress. Drought stress treatments have led to reductions in the stomatal conductance, transpiration, water potential and turgor pressure in leaves, and also the sap flow rate and osmotic hydraulic conductance in roots. In contrast, leaf osmotic pressure was increased in response to drought stress. Interestingly, the accumulation of NtPIP1;1 and NtPIP2;1 transcripts was significantly decreased, but only that of the NtAQP1 transcript was increased under drought stress. Functional analysis using Xenopus laevis oocytes revealed that NtPIP2;1 shows marked water transport activity, but the activities of NtAQP1 and NtPIP1;1 are weak or almost negligible, respectively, when expressed alone. However, co-expression of NtPIP1;1 with NtPIP2;1 significantly enhanced water transport activity compared with that of NtPIP1;1- or NtPIP2;1-expressing oocytes, suggesting that these two aquaporins may function as a water channel, forming a heterotetramer. Heteromerization of NtPIP1;1 and NtPIP2;1 was also suggested by co-expression analyses of NtPIP1;1-GFP (green fluorescent protein) and NtPIP2;1 in Xenopus oocytes. Re-watering treatments recovered water relation parameters and the accumulation of the three NtPIP transcripts to levels similar to control conditions. These results suggest that NtPIP1;1 and NtPIP2;1 play an important role in water transport in roots, and that expression of NtPIP1;1 and NtPIP2;1 is down-regulated in order to reduce osmotic hydraulic conductance in the roots of tobacco plants under drought stress.

DOI： 10.1093/pcp/pcn054

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PORTLAND PRESS LTD  

Background information. The results of water permeability measurements suggest the presence of an AQP (aquaporin) in the membrane of the CV (contractile vacuole) in Amoeba proteus [Nishihara, Shimmen and Sonobe (2004) Cell Struct. Funct. 29, 85-90].
Results. In the present study, we cloned an AQP gene from A. proteus [ApAQP (A. proteus AQP)] that encodes a 295-amino-acid protein. The protein has six putative TMs (transmembrane domains) and two NPA (Asn-Pro-Ala) motifs, which are conserved among various AQPs and are thought to be involved in the formation of water channels that span the lipid bilayer. Using Xenopus oocytes, we have demonstrated that the ApAQP protein product can function as a water channel. Immuncifluorescence microscopy with anti-ApAQP antibody revealed that ApAQP is detected on the CV membrane and on the vesicles around the CV. The presence of V-ATPase (vacuolar H+-ATPase) on the vesicle membrane around the CV was also detected.
Conclusions. Our data on ApAQP allow us to provide the first informed explanation of the high water permeability of the CV membrane in amoeba. Moreover, the results suggest that vesicles possessing V-ATPase are involved in generating an osmotic gradient. Based on our findings, we propose a new hypothesis for the mechanism of CV function.

DOI： 10.1042/BC20070091

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

The effects of male-derived extracts on female receptivity to remating were investigated in Callosobruchus chinensis (Coleoptera: Bruchidae). Injection of aqueous extracts of male reproductive tracts into the abdomen of females reduced receptivity. When aqueous extracts of male reproductive tracts were divided to three molecular weight (MW) fractions by ultrafiltration: &lt; 3, 3-14, and &gt; 14 kDa, the filtrate containing MW substances &lt; 3 kDa reduced female receptivity 3 h and I day after injection, whereas the fraction containing MW substances &gt; 14 kDa inhibited receptivity 2 and 4 days after injection. Finally, male reproductive tract organs were divided into accessory gland, seminal vesicle, and testis. Aqueous extracts of testis reduced receptivity of females on the second day and at 3 h, and aqueous extracts of accessory gland reduced receptivity of females on the second day after injection. On the other hand, aqueous extracts of seminal vesicle did not reduce female receptivity. The results indicate that more than one mechanism may be involved in producing the effects of male-derived substances on female receptivity; low MW male-derived substances, which possibly exist in testis, cause short-term inhibition, while high MW substances, which possibly exist in the accessory gland, inhibit female mating later than low MW substances in C chinensis. (c) 2007 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jinsphys.2007.11.009

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DOI： 10.1071/FP07/130

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：BLACKWELL PUBLISHING  

Root hydraulic conductivity (Lp(r)) and aquaporins were investigated in barley seedlings under salt stress of 100 mmol L-1 NaCl in hydroponic culture for 24 and 48 h. No reduction in root elongation was observed in stressed seedlings, and more that 75% of root and shoot growth was maintained under salt stress of 100 mmol L-1 NaCl. A slight increase in HvPIP2;1 transcript, which was the most abundant of the three aquaporins investigated, was observed. No significant changes in LPr and HvPIP2;1 protein were detected. The possible reason for these complicated results and the function of aquaporins in LPr under salt stress are discussed.

DOI： 10.1111/j.1747-0765.2007.00154.x

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記述言語：英語  

Soluble ionic aluminum (Al) inhibits root growth and reduces crop production on acid soils. Al-resistant cultivars of barley (Hordeum vulgare L.) detoxify Al by secreting citrate from the roots, but the responsible gene has not been identified yet. Here, we identified a gene (HvAACT1) responsible for the Al-activated citrate secretion by fine mapping combined with microarray analysis, using an Al-resistant cultivar, Murasakimochi, and an Al-sensitive cultivar, Morex. This gene belongs to the multidrug and toxic compound extrusion (MATE) family and was constitutively expressed mainly in the roots of the Al-resistant barley cultivar. Heterologous expression of HvAACT1 in Xenopus oocytes showed efflux activity for (14)C-labeled citrate, but not for malate. Two-electrode voltage clamp analysis also showed transport activity of citrate in the HvAACT1-expressing oocytes in the presence of Al. Overexpression of this gene in tobacco enhanced citrate secretion and Al resistance compared with the wild-type plants. Transiently expressed green fluorescent protein-tagged HvAACT1 was localized at the plasma membrane of the onion epidermal cells, and immunostaining showed that HvAACT1 was localized in the epidermal cells of the barley root tips. A good correlation was found between the expression of HvAACT1 and citrate secretion in 10 barley cultivars differing in Al resistance. Taken together, our results demonstrate that HvAACT1 is an Al-activated citrate transporter responsible for Al resistance in barley.

DOI： 10.1093/pcp/pcm091

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：NATURE PUBLISHING GROUP  

Silicon is an important nutrient for the optimal growth and sustainable production of rice(1-4). Rice accumulates up to 10% silicon in the shoot, and this high accumulation is required to protect the plant from multiple abiotic and biotic stresses(1-5). A gene, Lsi1, that encodes a silicon influx transporter has been identified in rice(6). Here we describe a previously uncharacterized gene, low silicon rice 2 (Lsi2), which has no similarity to Lsi1. This gene is constitutively expressed in the roots. The protein encoded by this gene is localized, like Lsi1, on the plasma membrane of cells in both the exodermis and the endodermis, but in contrast to Lsi1, which is localized on the distal side, Lsi2 is localized on the proximal side of the same cells. Expression of Lsi2 in Xenopus oocytes did not result in influx transport activity for silicon, but preloading of the oocytes with silicon resulted in a release of silicon, indicating that Lsi2 is a silicon efflux transporter. The identification of this silicon transporter revealed a unique mechanism of nutrient transport in plants: having an influx transporter on one side and an efflux transporter on the other side of the cell to permit the effective transcellular transport of the nutrients.

DOI： 10.1038/nature05964

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記述言語：英語   出版者・発行元：低温生物工学会  

Aquaporins are membrane proteins facilitating the membrane transport of water and low molecular weight compounds. Recent studies have indicated that aquaporins are involved in cellular tolerance mechanisms under low temperature stress in plants and insects. Critical roles of aquaporins in cold tolerance and the influence of H_2O_2 were suggested in the cucumber and figleaf gourd. Reduction of water uptake was observed in rice under chilling stress, in which the down-regulation of aquaporin expression and probable inactivation of aquaporins were involved. Glycerol and water transport by aquaporins was investigated, and revealed to be essential for freezing tolerance in insect cells.

DOI： 10.20585/cryobolcryotechnol.53.1_21

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記述言語：英語   出版者・発行元：OXFORD UNIV PRESS  

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記述言語：英語   出版者・発行元：OXFORD UNIV PRESS  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

PubMed

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記述言語：英語   出版者・発行元：Japanese Society for Root Research  

Aquaporins (water channels) are membrane proteins which facilitate the transport of water and low molecular weight compounds across biological membranes. The author and collaborators identified barley aquaporins and investigated the level of transcripts in roots, water transport activity, tissue localization, expression reduction by salt stress, and diurnal changes in the expression of a particular aquaporin. Over-expression of a barley aquaporin, HvPIP2;1, increased the shoot/root ratio and raised salt sensitivity in transgenic rice plants. Aquaporin research is providing significant insights into the water relations of plant roots.

DOI： 10.3117/plantroot.1.22

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC PLANT BIOLOGISTS  

The release of organic anions from roots can protect plants from aluminum (Al) toxicity and help them overcome phosphorus ( P) deficiency. Our previous findings showed that Al treatment induced malate and citrate efflux from rape ( Brassica napus) roots, and that P deficiency did not induce the efflux. Since this response is similar to the malate efflux from wheat ( Triticum aestivum) that is controlled by the TaALMT1 gene, we investigated whether homologs of TaALMT1 are present in rape and whether they are involved in the release of organic anions. We isolated two TaALMT1 homologs from rape designated BnALMT1 and BnALMT2 (B. napus Al-activated malate transporter). The expression of these genes was induced in roots, but not shoots, by Al treatment but P deficiency had no effect. Several other cations ( lanthanum, ytterbium, and erbium) also increased BnALMT1 and BnALMT2 expression in the roots. The function of the BnALMT1 and BnALMT2 proteins was investigated by heterologous expression in cultured tobacco ( Nicotiana tabacum) cells and in Xenopus laevis oocytes. Both transfection systems showed an enhanced capacity for malate efflux but not citrate efflux, when exposed to Al. Smaller malate fluxes were also activated by ytterbium and erbium treatment. Transgenic tobacco cells grew significantly better than control cells following an 18 h treatment with Al, indicating that the expression of BnALMT1 and BnALMT2 increased the resistance of these plant cells to Al stress. This report demonstrates that homologs of the TaALMT1 gene from wheat perform similar functions in other species.

DOI： 10.1104/pp.106.085233

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：NATURE PUBLISHING GROUP  

Silicon is beneficial to plant growth and helps plants to overcome abiotic and biotic stresses by preventing lodging ( falling over) and increasing resistance to pests and diseases, as well as other stresses(1-3). Silicon is essential for high and sustainable production of rice(4), but the molecular mechanism responsible for the uptake of silicon is unknown. Here we describe the Low silicon rice 1 (Lsi1) gene, which controls silicon accumulation in rice, a typical silicon-accumulating plant. This gene belongs to the aquaporin family(5) and is constitutively expressed in the roots. Lsi1 is localized on the plasma membrane of the distal side of both exodermis and endodermis cells, where casparian strips are located. Suppression of Lsi1 expression resulted in reduced silicon uptake. Furthermore, expression of Lsi1 in Xenopus oocytes showed transport activity for silicon only. The identification of a silicon transporter provides both an insight into the silicon uptake system in plants, and a new strategy for producing crops with high resistance to multiple stresses by genetic modification of the root's silicon uptake capacity.

DOI： 10.1038/nature04590

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：CROP SCIENCE SOC JAPAN  

We examined the differential elongation of gravitropically bending roots of Pisum sativum L. in terms of cell enlargement and water uptake by cells in the growing tissue. Hydraulic conductivity between the elongating and mature tissues (Lp) was estimated from the equation G = A x Lp x AT, where G is the water-uptake rate, A is the surface area of a single cell and AP is the driving force. The rate of entry of water into a cell was estimated from the rate of increase in the volumes of cells in the outer cortex, which were calculated from longitudinal sections at given times. Gravitropic bending occurred I h after the application of gravi-stimulation and the curvature increased rapidly for the next 3 h. The biggest difference in the partial elongation rate between opposite sides of a root was found in the region 3 to 4 mm from the root tip at the start of stimulation. Cell enlargement rate was 2.8 to 3.8 times greater on the upper side of the root than on the lower side. The water potential and the osmotic potential, in both the elongating and mature tissues, were the same on both sides of the root. Therefore, there was no difference in the driving force for water flow. Hydraulic conductivity was 2.3 to 4.2 times greater on the upper side of the root than on the lower side. There was no difference between the upper and lower sides of the root in the amounts of 19-kD and 24-kD proteins in membrane fractions, which we assumed to be aquaporins (putative aquaporins), as estimated with two preparations of polyclonal antibodies. The differential elongation that Occurred during root gravitropism was caused by a difference in Lp. However, the difference in Lp did not appear to be regulated by the concentration in cell membranes of the putative aquaporins.

DOI： 10.1626/pps.8.515

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER IRELAND LTD  

Reactive oxygen species (ROS)-related membrane lipid peroxidation in the root of Arabidopsis thaliana was fluorescently visualized and investigated under salt stress. In the control roots without salt stress, more fluorescence was observed in the elongating region than in the meristematic region. Salt stress of 100 mM NaCl enhanced the fluorescence in both, indicating that salt stress-induced ROS, and consequently membrane lipid peroxidation. In transgenic tobacco glutathione S-transferase over-expressing Arabidopsis (the parB plants), less fluorescence was observed than in the non-transgenic control plants. In the salt-stressed parB plant roots, the fluorescent brightness was reduced to 46% of that of the non-transgenic plant in the meristematic region. However, the inhibition of root growth was not improved in parB plants under salt stress at pH 5.7. That is, 100 mM of salt stress reduced the root growth to 40% or less both in the parent control plants and the parB plants. The root tissue osmotic pressure was almost the same between the two tested lines, which may be one of the reasons why no difference was observed in root growth between the two lines. These results suggested that salt stress-induced oxidative stress, and the introduction/overexpression of a glutathione S-transferase gene may have reduced the amount of ROS but the removal of ROS was not sufficient to effect salt tolerance because salt stress also caused an osmotic imbalance reducing the root growth. (c) 2005 Elsevier Ireland Ltd. All rights reserved.

DOI： 10.1016/j.plantsci.2005.03.030

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC  

A novel SmtB/ArsR family metalloregulator, denoted BxmR, has been identified and characterized from the cyanobacterium Oscillatoria brevis. Genetic and biochemical evidence reveals that BxmR represses the expression of both bxa1, encoding a CPx-ATPase metal transporter, as well as a divergently transcribed operon encoding bxmR and bmtA, a heavy metal sequestering metallothionein. Derepression of the expression of all three genes is mediated by both monovalent (Ag(I) and Cu(I)) and divalent (Zn(II) and Cd(II)) heavy metal ions, a novel property among SmtB/ArsR metal sensors. Electrophoretic gel mobility shift experiments reveal that apoBxmR forms multiple resolvable complexes with oligonucleotides containing a single 12-2-12 inverted repeat derived from one of the two operator/promoter regions with similar apparent affinities. Preincubation with either monovalent or divalent metal ions induces disassembly of both the BxmR-bxa1 and BxmR-bxmR/bmtA operator/promoter complexes. Interestingly, the temporal regulation of expression of bxa1 and bmtA mRNAs is different in O. brevis with bxa1 induced first upon heavy metal treatment, followed by bmtA/bxmR. A dynamic interplay among Bxa1, BmtA, and BxmR is proposed that maintains metal homeostasis in O. brevis by balancing the relative rates of metal storage and efflux of multiple heavy metal ions.

DOI： 10.1074/jbc.M310560200

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：BLACKWELL PUBLISHING LTD  

The major constraint to plant growth in acid soils is the presence of toxic aluminum (Al) cations, which inhibit root elongation. The enhanced Al tolerance exhibited by some cultivars of wheat is associated with the Al-dependent efflux of malate from root apices. Malate forms a stable complex with Al that is harmless to plants and, therefore, this efflux of malate forms the basis of a hypothesis to explain Al tolerance in wheat. Here, we report on the cloning of a wheat gene, ALMT1 (aluminum-activated malate transporter), that co-segregates with Al tolerance in F-2 and F-3 populations derived from crosses between near-isogenic wheat lines that differ in Al tolerance. The ALMT1 gene encodes a membrane protein, which is constitutively expressed in the root apices of the Al-tolerant line at greater levels than in the near-isogenic but Al-sensitive line. Heterologous expression of ALMT1 in Xenopus oocytes, rice and cultured tobacco cells conferred an Al-activated malate efflux. Additionally, ALMT1 increased the tolerance of tobacco cells to Al treatment. These findings demonstrate that ALMT1 encodes an Al-activated malate transporter that is capable of conferring Al tolerance to plant cells.

DOI： 10.1111/j.1365-313X.2003.01991.x

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

The internal conductance for CO2 diffusion (g(i)) and CO2 assimilation rate were measured and the related anatomical characteristics were investigated in transgenic rice leaves that overexpressed barley aquaporin HvPIP2;1. This study was performed to test the hypothesis that aquaporin facilitates CO2 diffusion within leaves. The g(i) value was estimated for intact leaves by concurrent measurements of gas exchange and carbon isotope ratio. The leaves of the transgenic rice plants that expressed the highest levels of Aq-anti-HvPIP2;1 showed a 40% increase in g(i) as compared to g(i) in the leaves of wild-type rice plants. The increase in g(i) was accompanied by a 14% increase in CO2 assimilation rate and a 27% increase in stomatal conductance (g(s)). The transgenic plants that had low levels of Aq-anti-HvPIP2;1 showed decreases in g(i) and CO2 assimilation rate. In the plants with high levels of Aq-anti-HvPIP2;1, mesophyll cell size decreased and the cell walls of the epidermis and mesophyll cells thickened, indicating that the leaves had become xeromorphic. Although such anatomical changes could partially offset the increase in g(i) by the aquaporin, the increase in aquaporin content overcame such adverse effects.

DOI： 10.1093/pcp/pch070

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記述言語：英語   出版者・発行元：OXFORD UNIV PRESS  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPANESE SOC SOIL SCIENCE PLANT NUTRITION  

Both root and shoot of barley seedlings showed continuous growth at night as well as in the daytime. Root hydraulic conductivity (Lp(r)) was monitored, and high Lp(r) values were recorded at night. For revealing the molecular mechanism, the presence of an aquaporin HvPIP2;1 in barley roots was investigated. The accumulation of the HvPIP2;1 transcript was mostly observed from the evening to the middle of the night. HvPIP2;1 protein was most abundant around midnight. As for tissue localization, HvPIP2;1 protein was abundant in cells involved in water transport. These results suggested the possible involvement of HvPIP2;1 in the mechanism of water transport in roots.

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

Barley HvPIP2;1 is a plasma membrane aquaporin and its expression was down-regulated after salt stress in barley [Katsuhara et al. (2002) Plant Cell Physiol. 43: 885]. We produced and analyzed transgenic rice plants over-expressing barley HvPIP2;1 in the present study. Overexpression of HvPIP2;1 increased (1) radial hydraulic conductivity of roots (Lp(r)) to 140%, and (2) the mass ratio of shoot to root up to 150%. In these transgenic rice plants under salt stress of 100 mM NaCl, growth reduction was greater than in non-transgenic plants. A decrease in shoot water content (from 79% to 61%) and reduction of root mass or shoot mass (both less than 40% of non-stressed plants) were observed in transgenic plants under salt stress for 2 weeks. These results indicated that over-expression of HvPIP2;1 makes rice plants sensitive to 100 mM NaCl. The possible involvement of aquaporins in salt tolerance is discussed.

DOI： 10.1093/pcp/pcg167

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

A metallothionein (BmtA) and a CPx-ATPase (Bxa1) have been identified and characterized from the cyanobacterium Oscillatoria brevis. Both bmtA and bxa1 expression can be markedly induced in vivo by Zn2+ or Cd2+. Over-expression of bmaA or bxa1 in Escherichia coli enhances Zn2+ and Cd2+ tolerance in the transformant. Dynamic studies on the expression of two genes showed that the maximum expression of bxa1 induced by Zn2+ and Cd2+ was much quicker than that of bmtA, suggesting distinct physiological roles of metallothionein and CPx-ATPase in the handling of surplus metal. (C) 2003 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.

DOI： 10.1016/S0014-5793(03)00370-3

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記述言語：英語   出版者・発行元：OXFORD UNIV PRESS  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC MICROBIOLOGY  

A novel gene related to heavy-metal transport was cloned and identified from the filamentous cyanobacterium Oscillatoria brevis. Sequence analysis of the gene (the Bxa1 gene) showed that its product possessed high homology with heavy-metal transport CPx-ATPases. The CPC motif, which is proposed to form putative cation transduction channel, was found in the sixth transmembrane helix. However, instead of the CXXC motif that is present in the N termini of most metal transport CPx-ATPases, Bxa1 contains a unique Cys-Cys (CC) sequence element and histidine-rich motifs as a putative metal binding site. Northern blotting and real-time quantitative reverse transcription-PCR showed that expression of Bxa1 mRNA was induced in vivo by both monovalent (Cu+ and Ag+) and divalent (Zn2+ and Cd2+) heavy-metal ions at similar levels. Experiments on heavy-metal tolerance in Escherichia coli with recombinant Bxa1 demonstrated that Bxa1 conferred resistance to both monovalent and divalent heavy metals. This is the first report of a CPx-ATPase responsive to both monovalent and divalent heavy metals.

DOI： 10.1128/JB.184.18.5027-5035.2002

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

We identified three genes homologous to water channels in the plasma membrane type subfamily from roots of barley seedlings. These genes were designated HvPIP2;1, HvPIP1;3, and HvPIP1;5 after comparison to Arabidopsis aquaporins. Competitive reverse transcription (RT)-PCR was applied in order to distinguish and to quantify their transcripts. The HvPIP2;1 transcript was the most abundant among the three in roots. Salt stress (200 mM NaCl) down-regulated HvPIP2;1 (transcript and protein), but had almost no effect on the expressions of HvPIP1;3, or HvPIP1;5. Approximately equal amounts of the transcripts of the three were detected in shoots, and salt stress enhanced the expression of HvPIP2;1 but not of HvPIP1;3, or HvPIP1;5. HvPIP2;1 protein was confirmed to be localized in the plasma membrane. Functional expression of HvPIP2;1 in Xenopus oocytes confirmed that HvPIP2;1 encoded an aquaporin that transports water. This water permeability was reduced by HgCl2, which is a typical water channel inhibitor. This activity was not modified by some inhibitors against protein kinase and protein phosphatase.

DOI： 10.1093/pcp/pcf102

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC PLANT BIOLOGISTS  

We have characterized the mechanism of action of four transgenes (AtBCB [Arabidopsis blue copper-binding protein], parB [tobacco {Nicotiana tabacum} glutathione S-transferase], NtPox [tobacco peroxidase], and NtGDI1 [tobacco GDP dissociation inhibitor]) that independently Al resistance on transgenic Arabidopsis. All four transgenic lines showed lower deposition of callose after Al treatment than the Landsberg erecta ecotype of Arabidopsis, confirming that the four genes function to ameliorate Al toxicity. Influx and efflux experiments of Al ions suggested that the AtBCB gene may suppress Al absorption, whereas expression of the NtGDI1 gene promotes a release of Al in the root tip region of Arabidopsis. The total enzyme activities of glutathione S-transferases or peroxidases in transoenic lines carrying either the parB or NtPox genes were significantly higher than in the Landsberg erecta ecotype of Arabidopsis, and these enzyme activities were maintained at higher levels during Al stress. Furthermore, lipid peroxidation caused by Al stress was repressed in these two transgenic lines, suggesting that overexpression of these two genes diminishes oxidative damage caused by Al stress. Al-treated roots of trans-enic plants were also stained by 4',6-diamino-2-phenylindole to monitor cell death caused by Al toxicity. The result suggested that cell death is repressed in the NtPox line. Analysis of F-1 hybrids between the four transgenic lines suggests that more resistant transgenic plants can be constructed by combinations of these four genes.

DOI： 10.1104/pp.127.3.918

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPANESE SOC SOIL SCIENCE PLANT NUTRITION  

A homologous gene to rice salT was isolated from barley and designated as Hv-salT, Since the expression of rice salT was regulated by plant hormones (abscisic acid and jasmonic acid) and salt stress, the effects of these plant hormones and salt stress on the growth of barley seedlings and the expression of Hv-salT were investigated. In contrast to rice salT, almost no changes in the expression of Hv-salT by hormones and salt stress were detected.

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC PLANT PHYSIOLOGISTS  

We have characterized transcripts for three potassium channel homologs in the AKT/KAT subfamily (Shaker type) from the common ice plant (Mesembryanthemum crystallinum), with a focus on their expression during salt stress (up to 500 mM NaCl). Mkt1 and 2, Arabidopsis AKT homologs, and Kmt1, a KAT homolog, are members of small gene families with two to three isoforms each. Mkt1 is root specific; Mkt2 is found in leaves, flowers, and seed capsules; and Kmt1 is expressed in leaves and seed capsules. Mkt1 is present in all cells of the root, and in leaves a highly conserved isoform is detected present in all cells with highest abundance in the vasculature. MKT1 for which antibodies were made is localized to the plasma membrane. Following salt stress, MKT1 (transcripts and protein) is drastically down-regulated, Mkt2 transcripts do not change significantly, and Kmt1 is strongly and transiently (maximum at 6 h) up-regulated in leaves and stems. The detection and stress-dependent behavior of abundant transcripts representing subfamilies of potassium channels provides information about tissue specificity and the complex regulation of genes encoding potassium uptake systems in a halophytic plant.

DOI： 10.1104/pp.125.2.604

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記述言語：英語   出版者・発行元：Japanese Society of Plant Physiologists  

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その他リンク： https://projects.repo.nii.ac.jp/?action=repository_uri&item_id=185274

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：TRANSACTION PERIOD CONSORTIUM  

A protocol is described for RNA in situ hybridization using thin sections prepared by Technovit resin. Technovit is a widely used resin for histological examinations. Since it does not require time-consuming processes such as removal of the resin and can be performed without high temperature treatment, a high resolution of sections could be possible compared to other resins and paraffin. Thin sections (approximately 4 mu m) were made from inflorescences of Arabidopsis thaliana embedded in Technovit 8100 resin, and in situ hybridization was performed using the protocol described in this article. Hybridization signals were observed using LEAFY and other genes as probes, showing that this resin can be used for in situ analysis. In our experiments, the most important factor for a successful in situ, hybridization pattern was to optimize the RNase A concentration after hybridization. We routinely used RNase A at a concentration of 2-5 ng/ml, a concentration much lower than that used for paraffin embedding method. Thus, the use of the Technovit resin for plant tissue embedding results in a faster protocol and greater quality than allowed by paraffin sections.

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Oxford University Press  

Salt stress-induced changes of intracellular pH and in levels of phosphorous compounds were monitored in intact root tips of barley seedlings (Hordeum vulgare cv. Akashinriki) by in vivo 31P-nuclear magnetic resonance (NMR) spectroscopy. Vacuolar alkalization was observed after treatment with both 300 and 500 mM NaCl. Much of the observed apparent alkalization of the cytoplasm was eliminated when the effect of Na+ ions on the titration curve was considered. Within 1 h after the initiation of salt stress, levels of glucose-6-phosphate and UDP-glucose decreased markedly, and such decreases might lead directly or indirectly to cell death. Simultaneous measurements of the external and intracellular pH revealed the promotion of external acidification and internal alkalization during salt stress. Possible mechanisms of Na+/H+ antiport at the tonoplast and the role of proton-pump in the plasma membrane are discussed.

DOI： 10.1093/oxfordjournals.pcp.a029146

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Japanese Society of Plant Physiologists  

Root growth of barley (Hordeum vulgare L., ev. Akashinriki) was inhibited by 200 mM NaCl, when 1 mM CaCl2 was present in the hydroponic culture solution. Increasing the CaCl2 up to 10 mM partially prevented this inhibition. However, inhibition also occurred with 100 mM NaCl in the presence of 0.1 mM CaCl2. The nuclei of meristematic cells in roots in which growth had been inhibited by salt stress were studied after staining with DAPI (4',6-diamino-2-phenylindol). Nuclear deformation of the cells occurred with 12 h of salt stress with 500 mM NaCl, and was followed by degradation. The nuclear degradation was also observed when the roots were exposed to more than 300 mM NaCl for 24 h. Biochemical analysis revealed that nuclear degradation was accompanied by apoptosislike DNA fragmentation. The intracellular mechanisms of nuclear degradation in cells after salt stress are discussed.

DOI： 10.1093/oxfordjournals.pcp.a028928

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記述言語：英語   出版者・発行元：Japanese Society of Plant Physiologists  

A quantitative analysis of organic acid in leaves of barnyard grass revealed that the contents of trans-aconitic acid were high, suggesting that this compound may act as an antifeedant against brown planthoppers. However, trans-aconitic acid could not be detected in the phloem sap which was considered to be the main nutrient source for brown planthoppers. trans-Aconitic acid was formed in vitro from cis-aconitic acid through the aconitate isomerase activity which was detected only in the leaf sheath, but not in the leaf blade.

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その他リンク： https://projects.repo.nii.ac.jp/?action=repository_uri&item_id=181825

記述言語：日本語   出版者・発行元：日本蠶絲學會  

クワ萎縮病の病原であるマイコプラズマ様微生物 (MLO) が, ベッコウハゴロモ (Ricania japonica Melichar) を用いたスタイレクトミー法 (YAGレーザー光線により昆虫の口針を切断) により採取された。すなわち, この方法で採取した萎縮病クワの師管液をDAPI (4′,6-ジアミジノ-2-フェニールインドール) で染色すると, 健全師管液では観察されない蛍光粒子としてMLOが観察された。さらに師管液を透過型電子顕微鏡で観察すると, 罹病クワ組織内と同形態のMLOが検出された。<br>一方, 萎縮病の媒介昆虫であるヨコバイ類および他の供試した数種の半翅目昆虫は, このレーザー・スタイレクトミー法には利用出来なかった。これら利用不能なヨコバイ類のレーザー切断口針は, 一部が脱落するなど著しく変形していたのに対し, 師管液が採取されたベッコウハゴロモの口針は, 組織内によく挿入されたままの状態で残ることが走査型電子顕微鏡により観察された。

DOI： 10.11416/kontyushigen1930.62.125

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その他リンク： http://agriknowledge.affrc.go.jp/RN/2010510238

掲載種別：研究論文（学術雑誌）   出版者・発行元：Oxford University Press ({OUP})  

DOI： 10.1093/oxfordjournals.pcp.a078072

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Abstract. The tonoplasts of internodal cells of Nitellopsis were removed by perfusing the vacuoles with media containing a Ca2 chelator, EGTA. Treatment of tonoplast‐free cells with 100 mol m3 NaCl induces a large membrane depolarization, a drastic decrease in the membrane resistance and an increase in Na+ influx. These events are identical to those that occur in intact cells subjected to high NaCl. These responses to NaCl are prevented if 10 mol m3 Ca2+ is supplied together with 100 mol m3 NaCl. The protective effect of Ca2+ is evident only when the intracellular ATP concentration exceeds 0.1 mol m3 and does not occur full when the intracellular ATP is removed. AMP at concentrations greater than 0.5 mol m3 or 0.25 mol m3 AMPPNP can replace ATP. It is concluded that ATP does not act as an energy source nor as a substrate for protein phosphorylation. ATP seems to exert its effects as a coeffector with Ca2+ in regulating the Na+ permeability of the plasma membrane. Copyright © 1990, Wiley Blackwell. All rights reserved

DOI： 10.1111/j.1365-3040.1990.tb01290.x

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：American Society of Plant Biologists  

Using the patch-clamp technique, we recorded single-channel currents across the excised patch of the plasma membrane of Nitellopsis. Both K+ and Na+ can pass this channel, but currents were not carried by Cl-. Upon the addition of ATP or AMP to the cytoplasmic side, the frequency of channel opening decreased. This is the first report on an ATP-regulated channel in plant cells.

DOI： 10.1104/pp.93.1.343

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Oxford University Press  

Cytoplasmic drops were prepared from internodal cells of the brackish Characeae Lamprothamnium succinctum. Applying the patch-clamp technique to single drops covered with tonoplast, we demonstrated the presence of Ca2+-regulated K+ channels in the tonoplast. In a cell-attached mode, the selectivity of such channels for K+ was about 50 times that for Na+. This channel showed a tendency to rectify in an outward direction. In the negative region of the pipette voltage, the conductance of this channel was 50 pS, while it was 100 pS in the positive voltage region. When the pipette voltage was increased above 50 mV, two conductance levels were found in the cell-attached mode as well as in the excised patch (cytoplasmic-side-out patch), which was obtained by pulling the patch pipette from the cytoplasmic drop under conditions of low levels of Ca2+. Using the excised patch, we controlled the level of Ca2+ on the cytoplasmic side of the channels. At a low level of Ca2+ (pCa=8) on the cytoplasmic side, the open frequency was very low and the opening time was short. An increase in Ca2+ on the cytoplasmic side (pCa = 5) increased both the frequency and the duration of opening. However, the conductance of the channels did not change. This regulation by Ca2+ of the K+ channels was reversible, that is, addition of EGTA on the cytoplasmic side inactivated the channels. The present study demonstrates a direct action of Ca2+ on the K+ channels. The physiological role of the K+ channel in the regulation of turgor in Lamprothamnium is discussed. © 1989 The Japanese Society of Plant Physiologists (JSPP).

DOI： 10.1093/oxfordjournals.pcp.a077774

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPANESE SOC PLANT PHYSIOLOGISTS  

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記述言語：英語   出版者・発行元：SPRINGER-VERLAG WIEN  

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記述言語：日本語  

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記述言語：日本語   出版者・発行元：日本作物学会  

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記述言語：日本語   出版者・発行元：一般社団法人日本土壌肥料学会  

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記述言語：日本語   出版者・発行元：日本応用動物昆虫学会  

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記述言語：日本語   出版者・発行元：一般社団法人日本土壌肥料学会  

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記述言語：日本語   出版者・発行元：養賢堂  

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記述言語：日本語   出版者・発行元：Japanese Society for Root Research  

水チャネル・アクアポリンの遺伝子が発見され, 細胞の水透過性と水輸送について, その分子機構を研究できるようになった. 私たちはオオムギ幼植物の根で発現している水チャネル遺伝子を同定し, その水輸送活性, 発現の組織的局在性, 発現量とその日周変化等を明らかにした. また水チャネルの発現が植物体の地上部/根の量比に影響することと, 耐塩性機構に関係していることを, 形質転換植物を使って示した. さらにこの形質転換体で, 二酸化炭素の葉内透過性が上昇していたことから, アクアポリンは水だけでなく, 二酸化炭素の膜透過を担っている可能性も示唆された.

DOI： 10.3117/rootres.13.15

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記述言語：日本語   出版者・発行元：一般社団法人日本土壌肥料学会  

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：OXFORD UNIV PRESS  

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記述言語：日本語   出版者・発行元：一般社団法人日本土壌肥料学会  

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：OXFORD UNIV PRESS  

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記述言語：日本語   出版者・発行元：裳華房  

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