Nagoya University · Agricultural and Biological Sciences
Professor Toshinori Kinoshita's research lab focuses on the molecular mechanisms regulating plasma membrane H⁺-ATPase in plant guard cells, particularly its role in stomatal opening and ion homeostasis. The lab investigates how this essential proton pump is activated by environmental signals such as blue light and phytohormones like brassinosteroids, through post-translational modifications including phosphorylation and 14-3-3 protein binding. Calcium signaling and the action of small molecules such as fusicoccin are also central to understanding the dynamic regulation of H⁺-ATPase activity. The research integrates cell biology, biochemistry, and molecular physiology to elucidate signal transduction pathways in plant cells.
Figures are computed from collected data and may differ slightly.
Opening of the stomata is driven by the light-activated plasma membrane proton pumping ATPase, although the activation and inactivation mechanism of the enzyme is not known. In this study, we show that the H+-ATPase in guard cells is reversibly inhibited by Ca2+ at physiological concentrations. Isolated microsomal membranes of guard cell protoplasts from fava bean exhibited vanadate-sensitive, ATP-dependent proton pumping. The activity was inhibited almost completely by 1 [mu]M Ca2+ with a half-
Phototropins are blue-light (BL) receptor serine (Ser)/threonine kinases, and contain two light, oxygen, and voltage (LOV) domains, and are members of the PAS domain superfamily. They mediate phototropism, chloroplast movement, leaf expansion, and stomatal opening of higher plants in response to BL. In stomatal guard cells, genetic analysis has revealed that phototropins mediate activation of the plasma membrane H+-ATPase by phosphorylation and drive stomatal opening. However, biochemical eviden
Toshinori Kinoshita, Mitsuo Nishimura, Ken-ichiro Shimazaki, Cytosolic Concentration of Ca2⁺ Regulates the Plasma Membrane H⁺-ATPase in Guard Cells of Fava Bean, The Plant Cell, Vol. 7, No. 8 (Aug., 1995), pp. 1333-1342
A fungal phytotoxin fusicoccin (FC) causes irreversible opening of stomata by activation of the plasma membrane H+-ATPase in guard cells. However, the mechanism by which FC activates the H+-ATPase is not fully understood with respect to the event of phosphorylation. In this study, we provide quantitative evidence that FC-dependent activation of H+-ATPase requires the phosphorylation of the C-terminus, and that FC maintains the activated state by preventing the dephosphorylation. The plasma membr
Blue light (BL) activates the plasma membrane H(+)-ATPase via phosphorylation of the C-terminus with concomitant binding of 14-3-3 protein to the terminus in stomatal guard cells. However, the binding site and role of 14-3-3 protein in this physiological response have not been elucidated. We investigated the above using synthetic phosphopeptides designed from the C-terminus of Vicia H(+)-ATPase (isoform 1; VHA1). The presence of KGLDIDTIQQHYphospho-T(950)V peptide (P-950) prevented binding of 14
Brassinosteroids (BRs) are steroid phytohormones that regulate plant growth and development, and promote cell elongation at least in part via the acid-growth process. BRs have been suggested to induce cell elongation by the activating plasma membrane (PM) H+-ATPase. However, the mechanism by which BRs activate PM H+-ATPase has not been clarified. In this study, we investigated the effects of BR on hypocotyl elongation and the phosphorylation status of a penultimate residue, threonine, of PM H+-A
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