title: Guard cell chloroplasts are essential for blue light-dependent stomatal opening in Arabidopsis.
abstract: Blue light (BL) induces stomatal opening through the activation of H+-ATPases with subsequent ion accumulation in guard cells. In most plant species, red light (RL) enhances BL-dependent stomatal opening. This RL effect is attributable to the chloroplasts of guard cell, the only cells in the epidermis possessing this organelle. To clarify the role of chloroplasts in stomatal regulation, we investigated the effects of RL on BL-dependent stomatal opening in isolated epidermis, guard cell protoplasts, and intact leaves of Arabidopsis thaliana. In isolated epidermal tissues and intact leaves, weak BL superimposed on RL enhanced stomatal opening while BL alone was less effective. In guard cell protoplasts, RL enhanced BL-dependent H+-pumping and DCMU, a photosynthetic electron transport inhibitor, eliminated this effect. RL enhanced phosphorylation levels of the H+-ATPase in response to BL, but this RL effect was not suppressed by DCMU. Furthermore, DCMU inhibited both RL-induced and BL-dependent stomatal opening in intact leaves. The photosynthetic rate in leaves correlated positively with BL-dependent stomatal opening in the presence of DCMU. We conclude that guard cell chloroplasts provide ATP and/or reducing equivalents that fuel BL-dependent stomatal opening, and that they indirectly monitor photosynthetic CO2 fixation in mesophyll chloroplasts by absorbing PAR in the epidermis.
authors.affiliation: Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Suetsugu
authors.affiliation: Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Tsuneaki
authors.initials: T
authors.lastname: Takami
authors.affiliation: Graduate School of System Life Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Yuuta
authors.initials: Y
authors.lastname: Ebisu
authors.affiliation: Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Harutaka
authors.initials: H
authors.lastname: Watanabe
authors.affiliation: Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Chihoko
authors.initials: C
authors.lastname: Iiboshi
authors.affiliation: Faculty of Art and Science, Kyushu University, Fukuoka, Japan.
authors.forename: Michio
authors.initials: M
authors.lastname: Doi
authors.affiliation: Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Ken-ichiro
authors.initials: K
authors.lastname: Shimazaki
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D002736:Chloroplasts / Q000187:drug effects / Q000502:physiology*; D004237:Diuron / Q000494:pharmacology; D008027:Light; D010766:Phosphorylation; D010788:Photosynthesis / Q000187:drug effects; D018515:Plant Leaves / Q000502:physiology; D010940:Plant Proteins / Q000378:metabolism; D054046:Plant Stomata / Q000187:drug effects / Q000502:physiology*; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D011523:Protoplasts / Q000166:cytology* / Q000187:drug effects
chemical_list: D010940:Plant Proteins; D004237:Diuron; D006180:Proton-Translocating ATPases