研究者詳細 - 且原　真木

論文 - 且原　真木

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Barley plasma membrane intrinsic proteins (PIP aquaporins) as water and CO(2) transporters

Maki Katsuhara, Yuko T. Hanba

PFLUGERS ARCHIV-EUROPEAN JOURNAL OF PHYSIOLOGY 456 ( 4 ) 687 - 691 2008年7月

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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Drought stress alters water relations and expression of PIP-type aquaporin genes in Nicotiana tabacum plants

Majid Mahdieh, Akbar Mostajeran, Tomoaki Horie, Maki Katsuhara

PLANT AND CELL PHYSIOLOGY 49 ( 5 ) 801 - 813 2008年5月

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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Presence of aquaporin and V-ATPase on the contractile vacuole of Amoeba proteus

Eri Nishihara, Etsuo Yokota, Akira Tazaki, Hidefurni Orii, Maki Katsuhara, Kensuke Kataoka, Hisako Igarashi, Yoshinori Moriyama, Teruo Shimmen, Seiji Sonobe

BIOLOGY OF THE CELL 100 ( 3 ) 179 - 188 2008年3月

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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Female mating receptivity inhibited by injection of male-derived extracts in Callosobruchus chinensis

Takashi Yamane, Yoshinobu Kimura, Maki Katsuhara, Takahisa Miyatake

JOURNAL OF INSECT PHYSIOLOGY 54 ( 2 ) 501 - 507 2008年2月

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: < 3, 3-14, and > 14 kDa, the filtrate containing MW substances < 3 kDa reduced female receptivity 3 h and I day after injection, whereas the fraction containing MW substances > 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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Expanding roles of plant aquaporins in plasma membranes and cell organelles.

Katsuhara, M, Hanba, T.Y, Shiratake, K, Maeshima, M

Functional Plant Biology 35 ( 1 ) 1 - 14 2008年

Barley root hydraulic conductivity and aquaporins expression in relation to salt tolerance

Maki Katsuhara, Mineo Shibasaka

SOIL SCIENCE AND PLANT NUTRITION 53 ( 4 ) 466 - 470 2007年8月

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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An aluminum-activated citrate transporter in barley.

Jun Furukawa, Naoki Yamaji, Hua Wang, Namiki Mitani, Yoshiko Murata, Kazuhiro Sato, Maki Katsuhara, Kazuyoshi Takeda, Jian Feng Ma

Plant & cell physiology 48 ( 8 ) 1081 - 91 2007年8月

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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An efflux transporter of silicon in rice

Jian Feng Ma, Naoki Yamaji, Namiki Mitani, Kazunori Tamai, Saeko Konishi, Toru Fujiwara, Maki Katsuhara, Masahiro Yano

NATURE 448 ( 7150 ) 209 - U12 2007年7月

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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Characterization of silicon permeability of NIP in gramineous plants 査読

Mitani Namiki, Yamaji Naoki, Katsuhara Maki, Ma Jian Feng

PLANT AND CELL PHYSIOLOGY 48 S30 2007年

Gene expression and functional analysis of a candidate gene related to Al-activated citrate transporter in barley 査読

Furukawa Jun, Yamaji Naoki, Wang Hua, Katsuhara Maki, Sato Kazuhiro, Takeda Kazuyoshi, Ma Jian Feng

Plant and Cell Physiology 48 S44 2007年

Low temperature and aquaporins, a molecular mechanism of water transport.

Katsuhara, M, Chung, G.C, Sakurai, J, Murai, M, Izumi, Y, Tsumuki, H

Cryobiology and Cryotechnology 53 ( 1 ) 21 - 32 2007年

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

CiNii Article

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Synchronous changes of aquaporins in rice seedlings during early phase of salt-stress.

Mineo Shibasaka, Maki Katsuhara

PLANT AND CELL PHYSIOLOGY 48 S162 - S162 2007年

Comparison of transpiration rates of naturalized and domestic Sedum species

Izumi Mori, Takashi Enomoto, Maki Katsuhara

PLANT AND CELL PHYSIOLOGY 48 S227 - S227 2007年

The BnALMT1 protein that is an aluminum-activated malate transporter is localized in the plasma membrane. 国際誌

Ligaba, A, Katsuhara, M, Sakamoto, W, Matsumoto, H

Plant signaling & behavior 2 ( 4 ) 1 - 2 2007年

Molecular mechanisms of water uptake and transport in plant roots: research progress with water channel aquaporins.

Katsuhara, M

Plant Root 1 22 - 26 2007年

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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The BnALMT1 and BnALMT2 genes from rape encode aluminum-activated malate transporters that enhance the aluminum resistance of plant cells

Ayalew Ligaba, Maki Katsuhara, Peter R. Ryan, Mineo Shibasaka, Hideaki Matsumoto

PLANT PHYSIOLOGY 142 ( 3 ) 1294 - 1303 2006年11月

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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A silicon transporter in rice

JF Ma, K Tamai, N Yamaji, N Mitani, S Konishi, M Katsuhara, M Ishiguro, Y Murata, M Yano

NATURE 440 ( 7084 ) 688 - 691 2006年3月

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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Hydraulic conductivity and aquaporins of cortical cells in gravitropically bending roots of Pisum sativum L.

N Miyamoto, M Katsuhara, T Ookawa, K Kasamo, T Hirasawa

PLANT PRODUCTION SCIENCE 8 ( 5 ) 515 - 524 2005年12月

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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Salt stress-induced lipid peroxidation is reduced by glutathione S-transferase, but this reduction of lipid peroxides is not enough for a recovery of root growth in Arabidopsis

M Katsuhara, T Otsuka, B Ezaki

PLANT SCIENCE 169 ( 2 ) 369 - 373 2005年8月

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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A novel cyanobacterial SmtB/ArsR family repressor regulates the expression of a CPx-ATPase and a metallothionein in response to both Cu(I)/Ag(I) and Zn(II)/Cd(II)

T Liu, S Nakashima, K Hirose, M Shibasaka, M Katsuhara, B Ezaki, DP Giedroc, K Kasamo

JOURNAL OF BIOLOGICAL CHEMISTRY 279 ( 17 ) 17810 - 17818 2004年4月

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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