||Kazuhiro Ishishita, Takeshi Higa, Hidekazu Tanaka, Shin Ichiro Inoue, Aeri Chung, Tomokazu Ushijima, Tomonao Matsushita, Toshinori Kinoshita, Masato Nakai, Masamitsu Wada, Noriyuki Suetsugu, Eiji Gotoh, Phototropin2 contributes to the chloroplast avoidance response at the chloroplast-plasma membrane interface, Plant physiology, 10.1104/pp.20.00059, 183, 5, 304-316, 2020.05, Blue-light-induced chloroplast movements play an important role in maximizing light utilization for photosynthesis in plants. Under a weak light condition, chloroplasts accumulate to the cell surface to capture light efficiently (chloroplast accumulation response). Conversely, chloroplasts escape from strong light and move to the side wall to reduce photodamage (chloroplast avoidance response). The blue light receptor phototropin (phot) regulates these chloroplast movements and optimizes leaf photosynthesis by controlling other responses in addition to chloroplast movements. Seed plants such as Arabidopsis (Arabidopsis thaliana) have phot1 and phot2. They redundantly mediate phototropism, stomatal opening, leaf flattening, and the chloroplast accumulation response. However, the chloroplast avoidance response is induced by strong blue light and regulated primarily by phot2. Phots are localized mainly on the plasma membrane. However, a substantial amount of phot2 resides on the chloroplast outer envelope. Therefore, differentially localized phot2 might have different functions. To determine the functions of plasma membrane- and chloroplast envelope-localized phot2, we tethered it to these structures with their respective targeting signals. Plasma membrane-localized phot2 regulated phototropism, leaf flattening, stomatal opening, and chloroplast movements. Chloroplast envelope-localized phot2 failed to mediate phototropism, leaf flattening, and the chloroplast accumulation response but partially regulated the chloroplast avoidance response and stomatal opening. Based on the present and previous findings, we propose that phot2 localized at the interface between the plasma membrane and the chloroplasts is required for the chloroplast avoidance response and possibly for stomatal opening as well..
||Miki Kihara, Tomokazu Ushijima, Yoshiyuki Yamagata, Yukinari Tsuruda, Takeshi Higa, Tomomi Abiko, Takahiko Kubo, Masamitsu Wada, Noriyuki Suetsugu, Eiji Gotoh, Light-induced chloroplast movements in Oryza species, Journal of Plant Research, 10.1007/s10265-020-01189-w, 2020.01, Light-induced chloroplast movements control efficient light utilization in leaves, and thus, are essential for leaf photosynthesis and biomass production under fluctuating light conditions. Chloroplast movements have been intensively analyzed using wild-type and mutant plants of Arabidopsis thaliana. The molecular mechanism and the contribution to biomass production were elucidated. However, the knowledge of chloroplast movements is very scarce in other plant species, especially grass species including crop plants. Because chloroplast movements are efficient strategy to optimize light capture in leaves and thus promote leaf photosynthesis and biomass, analysis of chloroplast movements in crops is required for biomass production. Here, we analyzed chloroplast movements in a wide range of cultivated and wild species of genus Oryza. All examined Oryza species showed the blue-light-induced chloroplast movements. However, O. sativa and its ancestral species O. rufipogon, both of which are AA-genome species and usually grown in open condition where plants are exposed to full sunlight, showed the much weaker chloroplast movements than Oryza species that are usually grown under shade or semi-shade conditions, including O. officinalis, O. eichingeri, and O. granulata. Further detailed analyses of different O. officinalis accessions, including sun, semi-shade, and shade accessions, indicated that the difference in chloroplast movement strength between domesticated rice plants and wild species might result from the difference in habitat, and the shape of mesophyll chlorenchyma cells. The findings of this study provide useful information for optimizing Oryza growth conditions, and lay the groundwork for improving growth and yield in staple food crop Oryza sativa..
||Eiji Gotoh, Kohei Oiwamoto, Shin Ichiro Inoue, Ken Ichiro Shimazaki, Michio Doi, Stomatal response to blue light in crassulacean acid metabolism plants Kalanchoe pinnata and Kalanchoe daigremontiana, Journal of Experimental Botany, 10.1093/jxb/ery450, 70, 4, 1367-1374, 2019.02, Blue light (BL) is a fundamental cue for stomatal opening in both C 3 and C 4 plants. However, it is unknown whether crassulacean acid metabolism (CAM) plants open their stomata in response to BL. We investigated stomatal BL responses in the obligate CAM plants Kalanchoe pinnata and Kalanchoe daigremontiana that characteristically open their stomata at night and close them for part of the day, as contrasted with C 3 and C 4 plants. Stomata opened in response to weak BL superimposed on background red light in both intact leaves and detached epidermal peels of K. pinnata and K. daigremontiana. BL-dependent stomatal opening was completely inhibited by tautomycin and vanadate, which repress type 1 protein phosphatase and plasma membrane H + -ATPase, respectively. The plasma membrane H + -ATPase activator fusicoccin induced stomatal opening in the dark. Both BL and fusicoccin induced phosphorylation of the guard cell plasma membrane H + -ATPase in K. pinnata. These results indicate that BL-dependent stomatal opening occurs in the obligate CAM plants K. pinnata and K. daigremontiana independently of photosynthetic CO 2 assimilation mode..
||Eiji Gotoh, Noriyuki Suetsugu, Wataru Yamori, Kazuhiro Ishishita, Ryota Kiyabu, Masako Fukuda, Takeshi Higa, Bungo Shirouchi, Masamitsu Wada, Chloroplast Accumulation Response Enhances Leaf Photosynthesis and Plant Biomass Production, Plant Physiology, 10.1104/pp.18.00484, 178, 3, 1358-1369, 2018.11, Under high light intensity, chloroplasts avoid absorbing excess light by moving to anticlinal cell walls (avoidance response), but under low light intensity, chloroplasts accumulate along periclinal cell walls (accumulation response). In most plant species, these responses are induced by blue light and are mediated by the blue light photoreceptor, phototropin, which also regulates phototropism, leaf flattening, and stomatal opening. These phototropin-mediated responses could enhance photosynthesis and biomass production. Here, using various Arabidopsis (Arabidopsis thaliana) mutants deficient in chloroplast movement, we demonstrated that the accumulation response enhances leaf photosynthesis and plant biomass production. Conspicuously, phototropin2 mutant plants specifically defective in the avoidance response but not in other phototropin-mediated responses displayed a constitutive accumulation response irrespective of light intensities, enhanced leaf photosynthesis, and increased plant biomass production. Therefore, our findings provide clear experimental evidence of the importance of the chloroplast accumulation response in leaf photosynthesis and biomass production..
||Gotoh Eiji, Suetsugu Noriyuki, Higa Takeshi, Matsushita Tomonao, Tsukaya Hirokazu, Wada Masamitsu, Palisade cell shape affects the light-induced chloroplast movements and leaf photosynthesis, SCIENTIFIC REPORTS, 10.1038/s41598-018-19896-9, 8, 2018.01, Leaf photosynthesis is regulated by multiple factors that help the plant to adapt to fluctuating light conditions. Leaves of sun-light-grown plants are thicker and contain more columnar palisade cells than those of shade-grown plants. Light-induced chloroplast movements are also essential for efficient leaf photosynthesis and facilitate efficient light utilization in leaf cells. Previous studies have demonstrated that leaves of most of the sun-grown plants exhibited no or very weak chloroplast movements and could accomplish efficient photosynthesis under strong light. To examine the relationship between palisade cell shape, chloroplast movement and distribution, and leaf photosynthesis, we used an Arabidopsis thaliana mutant, angustifolia (an), which has thick leaves that contain columnar palisade cells similar to those in the sun-grown plants. In the highly columnar cells of an mutant leaves, chloroplast movements were restricted. Nevertheless, under white light condition (at 120 µmol m−2 s−1), the an mutant plants showed higher chlorophyll content per unit leaf area and, thus, higher light absorption by the leaves than the wild type, which resulted in enhanced photosynthesis per unit leaf area. Our findings indicate that coordinated regulation of leaf cell shape and chloroplast movement according to the light conditions is pivotal for efficient leaf photosynthesis..
||Noriyuki Suetsugu*, Takeshi Higa*, Eiji Gotoh*, Masamitsu, Light-Induced Movements of Chloroplasts and Nuclei Are Regulated in Both Cp-Actin-Filament-Dependent and -Independent Manners in Arabidopsis thaliana, PLOS ONE, 10.1371/journal.pone.0157429, 11, 6, *These authors contributed equally., 2016.06.
||Ishishita Kazuhiro, Noriyuki Suetsugu, Yuki Hirose, Tomonao Matsushita, Takeshi Higa, Masamitsu Wada, Michio Doi, Eiji Gotoh, Functional characterization of blue-light-induced responses and PHOTOTROPIN 1 gene in Welwitschia mirabilis, JOURNAL OF PLANT RESEARCH, 10.1007/s10265-016-0790-7, 129, 2, 175-187, 2016.03.