Faculty Profiles - KATSUHARA Maki

Papers - KATSUHARA Maki

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T-DNA Tagging-Based Gain-of-Function of OsHKT1;4 Reinforces Na Exclusion from Leaves and Stems but Triggers Na Toxicity in Roots of Rice Under Salt Stress Reviewed

Oda Y, Kobayashi NI, Tanoi K, Ma JF, Itou Y, Katsuhara M, Itou T, Horie T

International Journal of Molecular Sciences 19 ( 1 ) 2018.1

Language：English Publishing type：Research paper (scientific journal) Publisher：MDPI

The high affinity K+ transporter 1;4 (HKT1;4) in rice (Oryza sativa), which shows Na+ selective transport with little K+ transport activity, has been suggested to be involved in reducing Na in leaves and stems under salt stress. However, detailed physiological roles of OsHKT1;4 remain unknown. Here, we have characterized a transfer DNA (T-DNA) insertion mutant line of rice, which overexpresses OsHKT1;4, owing to enhancer elements in the T-DNA, to gain an insight into the impact of OsHKT1;4 on salt tolerance of rice. The homozygous mutant (the O/E line) accumulated significantly lower concentrations of Na in young leaves, stems, and seeds than the sibling WT line under salt stress. Interestingly, however, the mutation rendered the O/E plants more salt sensitive than WT plants. Together with the evaluation of biomass of rice lines, rhizosphere acidification assays using a pH indicator bromocresol purple and (NaCl)-Na-22 tracer experiments have led to an assumption that roots of O/E plants suffered heavier damages from Na which excessively accumulated in the root due to increased activity of Na+ uptake and Na+ exclusion in the vasculature. Implications toward the application of the HKT1-mediated Na+ exclusion system to the breeding of salt tolerant crop cultivars will be discussed.

DOI： 10.3390/ijms19010235

Other Link： http://orcid.org/0000-0001-7545-2771

Identification of an H2O2permeable PIP aquaporin in barley and a serine residue promoting H2O2transport Reviewed

Rhee J, Horie T, Sasano S, Nakahara Y, Katsuhara M

Physiologia Plantarum 159 ( 1 ) 120 - 128 2017.1

Exogenous application of abscisic acid (ABA) increases root and cell hydraulic conductivity and abundance of some aquaporin isoforms in the ABA-deficient barley mutant Az34 Reviewed

Guzel Sharipova, Dmitriy Veselov, Guzel Kudoyarova, Wieland Fricke, Ian C. Dodd, Maki Katsuhara, Takuya Furuichi, Igor Ivanov, Stanislav Veselov

Annals of Botany 118 ( 4 ) 777 - 785 2016.10

Genome-Wide Characterization of Major Intrinsic Proteins in Four Grass Plants and Their Non-Aqua Transport Selectivity Profiles with Comparative Perspective

Abul Kalam Azad, Jahed Ahmed, Md. Asraful Alum, Md. Mahbub Hasan, Takahiro Ishikawa, Yoshihiro Sawa, Maki Katsuhara

PLOS ONE 11 ( 6 ) e0157735 2016.6

Language：English Publishing type：Research paper (scientific journal) Publisher：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

Phosphorus deprivation effects on water relations of Nicotiana tabacum plant via reducing plasma membrane permeability

M. Mahdieh, A. Mostajeran, M. Katsuhara

RUSSIAN JOURNAL OF PLANT PHYSIOLOGY 63 ( 1 ) 54 - 61 2016.1

Language：English Publishing type：Research paper (scientific journal) Publisher：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

OsHKT1;4-mediated Na+ transport in stems contributes to Na+ exclusion from leaf blades of rice at the reproductive growth stage upon salt stress

Kei Suzuki, Naoki Yamaji, Alex Costa, Eiji Okuma, Natsuko I. Kobayashi, Tatsuhiko Kashiwagi, Maki Katsuhara, Cun Wang, Keitaro Tanoi, Yoshiyuki Murata, Julian I. Schroeder, Jian Feng Ma, Tomoaki Horie

BMC PLANT BIOLOGY 16 ( 1 ) 22 2016.1

Language：English Publishing type：Research paper (scientific journal) Publisher：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

OsHKT2;2/1-mediated Na+ influx over K+ uptake in roots potentially increases toxic Na+ accumulation in a salt-tolerant landrace of rice Nona Bokra upon salinity stress

Kei Suzuki, Alex Costa, Hideki Nakayama, Maki Katsuhara, Atsuhiko Shinmyo, Tomoaki Horie

JOURNAL OF PLANT RESEARCH 129 ( 1 ) 67 - 77 2016.1

Language：English Publishing type：Research paper (scientific journal) Publisher：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

Yeast functional screen to identify genes conferring salt stress tolerance in Salicornia europaea

Yoshiki Nakahara, Shogo Sawabe, Kenta Kainuma, Maki Katsuhara, Mineo Shibasaka, Masanori Suzuki, Kosuke Yamamoto, Suguru Oguri, Hikaru Sakamoto

FRONTIERS IN PLANT SCIENCE 6 920 2015.10

Language：English Publishing type：Research paper (scientific journal) Publisher：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

Control of the Water Transport Activity of Barley HvTIP3;1 Specifically Expressed in Seeds

Shigeko Utsugi, Mineo Shibasaka, Masahiko Maekawa, Maki Katsuhara

PLANT AND CELL PHYSIOLOGY 56 ( 9 ) 1831 - 1840 2015.9

Language：English Publishing type：Research paper (scientific journal) Publisher：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

Dynamic Regulation of the Root Hydraulic Conductivity of Barley Plants in Response to Salinity/Osmotic Stress

Toshiyuki Kaneko, Tomoaki Horie, Yoshiki Nakahara, Nobuya Tsuji, Mineo Shibasaka, Maki Katsuhara

PLANT AND CELL PHYSIOLOGY 56 ( 5 ) 875 - 882 2015.5

Language：English Publishing type：Research paper (scientific journal) Publisher：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

Osmotic stress decreases PIP aquaporin transcripts in barley roots but H2O2 is not involved in this process

Maki Katsuhara, Nobuya Tsuji, Mineo Shibasaka, Sanjib Kumar Panda

JOURNAL OF PLANT RESEARCH 127 ( 6 ) 787 - 792 2014.11

Language：English Publishing type：Research paper (scientific journal) Publisher：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

Expression of root HvPIPs of barley seedling under chilling stress

Rui-Jun Duan, Hui-Yan Xiong, Katsuhara Maki

Zhiwu Shengli Xuebao/Plant Physiology Journal 50 ( 8 ) 1203 - 1208 2014.8

Language：Chinese Publishing type：Research paper (scientific journal) Publisher：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

CO2 Transport by PIP2 Aquaporins of Barley

Izumi C. Mori, Jiye Rhee, Mineo Shibasaka, Shizuka Sasano, Toshiyuki Kaneko, Tomoaki Horie, Maki Katsuhara

PLANT AND CELL PHYSIOLOGY 55 ( 2 ) 251 - 257 2014.2

Language：English Publishing type：Research paper (scientific journal) Publisher：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

Functional and molecular characteristics of rice and barley NIP aquaporins transporting water, hydrogen peroxide and arsenite

Maki Katsuhara, Shizuka Sasano, Tomoaki Horie, Tadashi Matsumoto, Jiye Rhee, Mineo Shibasaka

PLANT BIOTECHNOLOGY 31 ( 3 ) 213 - U173 2014

Language：English Publishing type：Research paper (scientific journal) Publisher：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

The photosynthetic response of tobacco plants overexpressing ice plant aquaporin McMIPB to a soil water deficit and high vapor pressure deficit

Miki Kawase, Yuko T. Hanba, Maki Katsuhara

JOURNAL OF PLANT RESEARCH 126 ( 4 ) 517 - 527 2013.7

Language：English Publishing type：Research paper (scientific journal) Publisher：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

Overexpression of Alternative Oxidase Gene Confers Aluminum Tolerance by Altering the Respiratory Capacity and the Response to Oxidative Stress in Tobacco Cells

Sanjib Kumar Panda, Lingaraj Sahoo, Maki Katsuhara, Hideaki Matsumoto

MOLECULAR BIOTECHNOLOGY 54 ( 2 ) 551 - 563 2013.6

Language：English Publishing type：Research paper (scientific journal) Publisher：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

Water and CO2 permeability of SsAqpZ, the cyanobacterium Synechococcus sp. PCC7942 aquaporin

Xiaodong Ding, Tadashi Matsumoto, Patrizia Gena, Chengwei Liu, Marialuisa Pellegrini-Calace, Shihua Zhong, Xiaoli Sun, Yanming Zhu, Maki Katsuhara, Ikuko Iwasaki, Yoshichika Kitagawa, Giuseppe Calamita

Biology of the Cell 105 ( 3 ) 118 - 128 2013.3

Language：English Publishing type：Research paper (scientific journal)

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

Rice sodium-insensitive potassium transporter, OsHAK5, confers increased salt tolerance in tobacco BY2 cells

NAKAYAMA Pulla K

生物工学会誌 : seibutsu-kogaku kaishi 91 ( 2 ) 85 - 85 2013.2

Aquaporin OsPIP1;1 promotes rice salt resistance and seed germination

Chengwei Liu, Tatsuya Fukumoto, Tadashi Matsumoto, Patrizia Gena, Daniele Frascaria, Tomoyuki Kaneko, Maki Katsuhara, Shihua Zhong, Xiaoli Sun, Yanming Zhu, Ikuko Iwasaki, Xiaodong Ding, Giuseppe Calamita, Yoshichika Kitagawa

PLANT PHYSIOLOGY AND BIOCHEMISTRY 63 151 - 158 2013.2

Language：English Publishing type：Research paper (scientific journal) Publisher：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

Salinity tolerance mechanisms in glycophytes: An overview with the central focus on rice plants. Reviewed

Horie T, Karahara I, Katsuhara M

Rice (New York, N.Y.) 5 ( 1 ) 11 - 11 2012.12

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