査読あり, 英語, Plant, Cell and Environment, Ion gradients in xylem exudate and guttation fluid related to tissue ion levels along primary leaves of barley, Makiko Nagai; Miwa Ohnishi; Takeo Uehara; Mutsumi Yamagami; Eiko Miura; Mai Kamakura; Akira Kitamura; Shu-Ichi Sakaguchi; Wataru Sakamoto; Teruo Shimmen; Hidehiro Fukaki; Robert J. Reid; Akio Furukawa; Tetsuro Mimura, The concentration of ions in plant cells and tissues is an essential factor in determining physiological function. In the present study, we established that concentration gradients of mobile ions exist in both xylem exudates and tissues within a barley (Hordeum vulgare) primary leaf. For K+ and NO3-, ion concentrations generally decreased from the leaf base to the tip in both xylem exudates and tissues. Ion gradients were also found for Pi and Cl- in the xylem. The hydathode strongly absorbed Pi and re-translocated it to the rest of the plant, whereas Cl- was extruded. The ion concentration gradients developed early during leaf growth, increased as the tissue aged and remained under both high and low transpiration conditions. Measurement of the expression profiles of Pi, K+ and NO3- transporters along the longitudinal axis of the leaf revealed that some transporters are more expressed at the hydathode, but for most transporters, there was no significant variation along the leaf. The mechanisms by which longitudinal ion gradients develop in leaves and their physiological functions are discussed. © 2013 John Wiley &
Sons Ltd., 2013年10月, 36, 10, 1826, 1837, 研究論文(学術雑誌), 10.1111/pce.12090
査読あり, 英語, JOURNAL OF GENERAL AND APPLIED MICROBIOLOGY, Unique profiles of changes in cell membrane fluidity during ethanol-induced yeast-to-pseudohyphal transition in Candida tropicalis, Takahito Suzuki; Keita Kono; Shu-ichi Tawara; Takaji Fujimura; Takuya Ito; Kazuo Omi; Kaoru Ohbuchi; Yasuhiko Komatsu; Shuichi Sakaguchi; Teijiro Kamihara, A dimorphic transition from the yeast form to filamentous one in Candida tropicalis pK233 is triggered by the addition of ethanol into the glucose semi-defined liquid medium and the process of filamentation accompanies temporal depolarization of yeast cells. The transition is completely prevented by further supplementation of myo-inositol at the start of cultivation. The addition of ethanol caused an increase in membrane fluidity during the process of depolarization, and then fluidity was gradually lowered to the level equivalent with that of the stationary-phase yeast cells in accordance with filamentation. The increase in membrane fluidity of ethanol-induced cells appeared parallel with reduction in the content of membrane phosphatidylinositol, which was rich in saturated palmitic acid. Introduction of exogenous myo-inositol or 1 m sorbitol into the ethanol-supplemented culture at the start of cultivation restored yeast growth and the reduction of membrane fluidity occurred, coupled with the recovery of the phosphatidylinositol content., 2010年08月, 56, 4, 321, 329, 研究論文(学術雑誌)
査読あり, 英語, Plant Morphology, Somaclonal variation and the ploidy Level in Phalaenopsis alliance., 坂口修一; 周天甦, 2003年, 15, 1, 2-7
査読あり, 英語, PROTOPLASMA, Development and disintegration of phragmoplasts in living cultured cells of a GFP :: TUA6 transgenic Arabidopsis thaliana plant, K Ueda; S Sakaguchi; F Kumagai; S Hasezawa; H Quader; U Kristen, Cultured suspension cells of Arabidopsis thaliana that stably express a green-fluorescent protein-alpha-tubulin 6 fusion protein were used to follow the development and disintegration of phragmoplasts. The development and disintegration of phragmoplasts in the living cultured cells could be successively observed by detecting the green-fluorescent protein fluorescence of the microtubules. In the early telophase spindle, where two kinetochore groups and two daughter chromosome groups had completely separated from one another, fluorescence appeared in the interzone between the two chromosome groups. The fluorescent region was gradually condensed at the previous equator and increased in fluorescence intensity, and finally it formed the initial phragmoplast. The initial phragmoplast moved from the cell center towards the cell periphery, and it lost fluorescence at its center and became double rings in shape. The expansion orientation of the phragmoplast was not always the same as that of the future new cell wall before it came in contact with the cell wall. The phragmoplast did not usually come in contact with the cell wall simultaneously with its entire length. A portion of the phragmoplast which was earlier in contact with the cell wall disappeared earlier than other portions of the phragmoplast. The duration of contact between any portions of the phragmoplast and the plasma membrane of the cell wall was 15-30 min. The fluorescence intensity of the cytoplasm did not seem to be elevated by the disintegration of the strongly fluorescent phragmoplast., 2003年, 220, 3-4, 111, 118, 研究論文(学術雑誌), 10.1007/s00709-002-0049-0
査読あり, 日本語, Plant Morphology, ナツミカンCitrus natsudaidai Hayata果実の毛状体の起源と発生., 坂口修一; 杉山明子, 2002年, 14, 1, 29-33
査読あり, 英語, CELL STRUCTURE AND FUNCTION, Ca2+ signal is generated only once in the mating pheromone response pathway in Saccharomyces cerevisiae, J Nakajima-Shimada; S Sakaguchi; F Tsuji; Y Anraku; H Iida, The mating pheromone, alpha-factor, of the yeast Saccharomyces cerevisiae binds to the heterotrimeric G protein-coupled cell surface receptor of MATa cells and induces cellular responses necessary for mating. In higher eukaryotic cells, many hormones and growth factors rapidly mobilize a second messenger, Ca2+, by means of receptor-C protein signaling. Although striking similarities between the mechanisms of the receptor-G protein signaling in yeast and higher eukaryotes have long been known, it is still uncertain whether the pheromone rapidly mobilizes Ca2+ necessary for early events of the pheromone response. Here we reexamine this problem using. sensitive methods for detecting Ca2+ fluxes and mobilization, and find no evidence that there is rapid Ca2+ influx leading to a rapid increase in the cytosolic free Ca2+ concentration. In addition, the yeast PLC1 deletion mutant lacking phosphoinositide-specific phospholipase C, a hey enzyme for generating Ca2+ signals in higher eukaryotic cells, responds normally to the pheromone. These findings suggest that the receptor-G protein signaling does not utilize Ca2+ as a second messenger In the early stage of the pheromone response pathway, Since the receptor-G protein signaling does stimulate Ca2+ influx after early events have finished and this stimulation is essential for late events in the pheromone response pathway {Iida et al,, (1990) J, Biol, Chem., 265: 13391-13399} Ca2+ may be used only once in the signal transduction pathway in unicellular eukaryotes such as yeast., 2000年04月, 25, 2, 125, 131, 研究論文(学術雑誌)
査読あり, 英語, Mycoscience, Roles of Ca2+ in hyphal and yeast-form growth in Candida albicans. Growth regulation by altered extracellular and intracellular free Ca2+ concentrations, Shuichi Sakaguchi; Kyoko Shibuya; Hidetoshi Iida; Yasuhiro Anraku; Takahito Suzuki, The dimorphic fungus Candida albicans has both a yeast form and a hyphal form. When yeast-form cells were starved and then transferred to a N-acetylglucosamine medium, the formation of true hyphae from the unbudded yeast-form cells was induced. Removal of Ca2+ from the medium with EGTA inhibited hyphal formation by 50%, resulting in only thin and short hyphae. Externally applied excess Ca2+ (>
10-2 M) also affected the hyphal formation, resulting in formation of pseudohyphae. This effect required a high concentration of Ca2+ but was Ca2+-specific. Deprivation of Ca2+ also inhibited yeast-form growth. Interestingly, such cells had abnormally wide bud necks and became defective in cell separation. To measure cytosolic free Ca2+, fura-2 was introduced into hyphal cells by electroporation. Its normal value was estimated to be about 100 nM. The electroporation caused transient elevation of cytosolic free Ca2+ concentration and transient cessation of hyphal growth. There was a close correlation between the timing of recovery of Ca2+ concentration and that of the resumption of hyphal growth. Our results demonstrate the importance of extracellular and intracellular free Ca2+ for the growth of C. albicans., 1997年, 38, 2, 215, 225, 研究論文(学術雑誌), 10.1007/BF02460856
査読無し, 英語, PROTOPLASMA, Overproduction of Cdc24p (Cls4p), a guanine nucleotide-exchange factor toward Cdc42 GTPase, impairs initiation of budding in Saccharomyces cerevisiae, S Sakaguchi; S Miyamoto; H Iida; T Suzuki; Y Ohya; Y Anraku, An entire coding region of the CDC24/CLS4 gene and its truncated derivatives were overexpressed in yeast cells under the control of the GAL1 promoter. Western blotting analysis of the yeast cell lysates showed that the CDC24/CLS4 protein (Cdc24p) was induced to reach its maximum level after 9 h incubation of the cells in galactose medium. Overexpression of Cdc24p within the cells caused the morphological change, accumulating large spherical unbudded cells which exhibited actin cytoskeleton disturbed, chitin delocalized on the cell surface, and cell viability decreased. Multiple nuclei were observed in these cells, indicating that only budding cycle bur not nuclear division cycle is blocked by the overproduction of Cdc24p. In order to identify the region of Cdc24p responsible for the growth inhibition, several truncated CDC24 genes were expressed. Surprisingly, overexpression of fragments either containing the C-terminal 76 amino acid residues or deleting the same region inhibited cellular growth. This suggests that Cdc24p contains multiple functional domains for its tasks, likely cooperating signals of bud positioning and bud timing., 1995年, 189, 3-4, 142, 148, 研究論文(学術雑誌)
査読あり, 英語, Protoplasma, Overproduction of Cdc24p(cls4p), a GTP-GDP exchange factor toward Cdc42 GTPase impairs initiation of budding in Saccharomyces cerevisiae., 坂口修一; 大矢禎一他, 1995年, 189, 3-4, 142-148
査読あり, 英語, MICROBIOLOGY-UK, OCCURRENCE OF CHROMOSOME REARRANGEMENTS DURING THE FUSION PROCESS IN THE IMPERFECT YEAST CANDIDA-ALBICANS, T SUZUKI; M YAMADA; S SAKAGUCHI, Auxotrophic derivatives of three strains of the pathogenic yeast Candida albicans of different origins, including 1006 derived from CBS5736, A5153 derived from FC18 and NARA2 derived from NUM961, were used in spheroplast fusion experiments. The DNA content of the prototrophic fusion product obtained following fusion between strains 1006 and A5153 approximated to the sum of those of the parents, but was variable when NARA2 was used as the parent for fusion. Chromosome-sized DNA molecules of the fusion derivatives were separated by pulsed-field gel electrophoresis to examine whether either or both of the chromosome-sized DNA molecules of each parent were transferred into the fusion derivatives. In the fusion derivatives obtained following fusion between strains 1006 and A5153, nearly the full complement of chromosomes was shown to be transferred, but partial transfer of chromosomes occurred in the fusion derivatives that were obtained following fusion between strains NARA2 and A5153. Results indicated that chromosome loss also occurred when these two strains were fused. Variations in the size of R chromosomes, the rDNA-containing chromosomes, were observed in all fusion derivatives tested, indicating high-frequency recombination between R chromosomes during the fusion process., 1994年12月, 140, 3319, 3328, 研究論文(学術雑誌)
査読あり, 英語, JOURNAL OF BACTERIOLOGY, CORRELATION BETWEEN POLYPLOIDY AND AUXOTROPHIC SEGREGATION IN THE IMPERFECT YEAST CANDIDA-ALBICANS, T SUZUKI; A HITOMI; PT MAGEE; S SAKAGUCHI, In order to clarify the relationship between polyploidization and the capability of phenotypic switching in the imperfect yeast Candida albicans, two types of variants were isolated as segregants from a fusant, which produced a proportion of the cell population with a higher ploidy than the rest, either in a temperature-dependent or -independent manner, when incubated at low (28 degrees C) and high (37 degrees C) temperatures. In the case of the temperature-dependent type of variants, high-ploidy cells appeared at 37 degrees C but rarely at 28 degrees C. This phenotype was named Pld(ts) (temperature-sensitive polyploidization), and the temperature-independent phenotype was called Pld(-). The appearance of high-ploidy cells in the culture of the Pld(ts) strain at 37 degrees C was accompanied by a significant increase in the frequency of auxotrophic variants; these variants probably occur as a result of segregation of auxotrophic markers from the heterozygous to the homozygous state. Both Pld(ts) and Pld(-) phenotypes were recessive in a fusion with a Pld(+) parent. An adenine auxotrophic marker (ade1) was introduced into a Pld(ts) strain in a heterozygous state, and the individual high-ploidy cells of this strain, grown at 37 degrees C, were micromanipulated to form colonies, which consisted of red and white sectors appearing at high frequency on a pink background. When the ade1 auxotrophy was introduced into Pld(-) strains, frequently sectored colonies were produced. These results suggested an increased level of chromosome missegregation in both types of Pld mutants. Analyses by pulsed-field gel electrophoresis of Ade(-) segregants, derived from a micromanipulated high-ploidy cell of a Pld(ts) strain, suggested the occurrence of nonreciprocal recombination, some of which includes chromosome loss., 1994年06月, 176, 11, 3345, 3353, 研究論文(学術雑誌)
査読あり, 英語, BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS, A DBL-HOMOLOGOUS REGION OF THE YEAST CLS4/CDC24 GENE-PRODUCT IS IMPORTANT FOR CA2+-MODULATED BUD ASSEMBLY, S MIYAMOTO; Y OHYA; Y SANO; S SAKAGUCHI; H IIDA; Y ANRAKU, 1991年12月, 181, 2, 604, 610, 研究論文(学術雑誌)
査読あり, 英語, JOURNAL OF BIOLOGICAL CHEMISTRY, CELL-CYCLE CONTROL BY CA-2+ IN SACCHAROMYCES-CEREVISIAE, H IIDA; S SAKAGUCHI; Y YAGAWA; Y ANRAKU, 1990年12月, 265, 34, 21216, 21222, 研究論文(学術雑誌)
査読あり, 英語, BOTANICAL MAGAZINE-TOKYO, SPECIFIC ARRANGEMENTS OF CORTICAL MICROTUBULES ARE CORRELATED WITH THE ARCHITECTURE OF MERISTEMS IN SHOOT APICES OF ANGIOSPERMS AND GYMNOSPERMS, S SAKAGUCHI; T HOGETSU; N HARA, 1990年06月, 103, 1070, 143, 163, 研究論文(学術雑誌)
査読あり, 英語, BOTANICAL MAGAZINE-TOKYO, ARRANGEMENT OF CORTICAL MICROTUBULES AT THE SURFACE OF THE SHOOT APEX IN VINCA-MAJOR L - OBSERVATIONS BY IMMUNOFLUORESCENCE MICROSCOPY, S SAKAGUCHI; T HOGETSU; N HARA, 1988年12月, 101, 1064, 497, 507, 研究論文(学術雑誌)
査読あり, 英語, PLANTA, ARRANGEMENT OF CORTICAL MICROTUBULES IN THE SHOOT APEX OF VINCA-MAJOR L - OBSERVATIONS BY IMMUNOFLUORESCENCE MICROSCOPY, S SAKAGUCHI; T HOGETSU; N HARA, 1988年09月, 175, 3, 403, 411, 研究論文(学術雑誌)
査読あり, 英語, PLANT AND CELL PHYSIOLOGY, INTRA-LEAF AND INTRACELLULAR GRADIENTS IN CHLOROPLAST ULTRASTRUCTURE OF DORSIVENTRAL LEAVES ILLUMINATED FROM THE ADAXIAL OR ABAXIAL SIDE DURING THEIR DEVELOPMENT, TERASHIMA, I; S SAKAGUCHI; N HARA, 1986年09月, 27, 6, 1023, 1031, 研究論文(学術雑誌)
植物学の百科事典, 丸善出版, 坂口修一; 相田光宏, 分担, 2016年06月, 536-539, 542-543, 日本語, 査読無し, その他
Atlas of Plant Cell Structure, Springer, 坂口修一; Tetsuko Noguchi, 分担, 2014年09月, 134-135, 英語, 査読無し, その他, 9784431549406
岩波生物学辞典、第五版, 岩波書店, 坂口修一; 相羽惠介, 分担, 2013年02月, 63--1476中の56ヵ所, 日本語, 査読無し, その他
生物学辞典, 東京化学同人, 坂口修一; 相川真一, 分担, 2010年12月, p. 337他、71カ所, 日本語, 査読無し, その他
これでナットク!植物の謎 植木屋さんも知らないたくましいその生き方\n(ブルーバックスB-1565), 講談社, 坂口修一; 浅田浩二, その他, 2007年08月, 71-73, 73-78, 103-106, 日本語, 査読無し, その他
食Up to Date - 食と健康|食と安全|食と環境 -, 金芳堂、京都, 坂口修一; 松田覚他, 分担, 2005年01月, pp. 194-211, 日本語, 査読無し, その他
2011年, X線CT顕微鏡法によるシロイヌナズナ胚の非破壊構造解析, 0, 0, 0, 競争的資金
2011年, Analysis of cellular arrangements in Arabidopsis embryo as revealed by micro X-ray computer tomography method., 0, 0, 0, 競争的資金
2008年, 2010年, 環境に配慮した遺伝子組換えサツマイモの作出に関する基礎的研究, 0, 0, 0, 環境中に逃げ出しても子孫を残せない、または、容易に識別可能で防除可能なサツマイモの作出に関し複数の観点からアプローチする。, 競争的資金
2008年, 2010年, Fundamental study on the novel transgenic sweetpotatos to minimize the undesirable effect on ecological system, 0, 0, 0, 競争的資金
2006年, 植物の姿勢制御に関する研究, 0, 0, 0, ランなどの左右相称花の向きが重力により調整される現象や、要面が葉柄のねじれ運動により天空方向を向くように調節される現象をタイムラプス撮影等により観察するとともに、現象に関与するメカニズムを生理学、遺伝学的に解析している, 競争的資金
2006年, Studies on phenomena of posture control of plants, 0, 0, 0, 競争的資金
2001年, GFPを用いた植物細胞における微小管の動的観察, 0, 0, 0, これまでにシロイヌナズナのGFP-tubulin導入植物体および培養細胞を用いて隔壁形成体などの動的変化等を明らかにした。, 競争的資金
2001年, Visualization of microtubules in living plant cells using GFP, 0, 0, 0, 競争的資金
1999年, コチョウランの培養変異に関する研究, 0, 0, 0, 競争的資金
1999年, Studies on Somaclonal Variation in Phalaenopsis, 0, 0, 0, 競争的資金
1994年, 植物細胞の細胞骨格制御にかかわる情報伝達系, 0, 0, 0, 競争的資金
1994年, Signal transduction of cytoskeletal control in plant, 0, 0, 0, 競争的資金
1992年, トランスジェニック植物を用いたクローン解析, 0, 0, 0, 競争的資金
1992年, Clonal analysis using transgenic plants, 0, 0, 0, 競争的資金
1987年, 茎頂における形態形成, 0, 0, 0, 茎頂からの葉の発生機構に関し、葉序の転換現象や不規則型葉序の記載学的研究にあわせ、微小管の配列やオーキシンの役割について解析を進めている。, 競争的資金
1987年, Morphogenesis in the Shoot apex, 0, 0, 0, 競争的資金
高等植物の組織・細胞観察, 0, 0, 0, 競争的資金
Examination of Cells and Tissues of Higher Plants, 0, 0, 0, 競争的資金