title: Photosynthetic control of the plasma membrane H+-ATPase in Vallisneria leaves. I. Regulation of activity during light-induced membrane hyperpolarization.
abstract: In mesophyll cells of the aquatic angiosperm Vallisneria gigantea Graebner, red, blue, or blue plus far-red light induced a typical membrane hyperpolarization, whereas far-red light alone had little effect. Both N,N'-dicyclohexylcarbodiimide, a potent inhibitor of H+-ATPase, and carbonylcyanide m-chlorophenylhydrazone, an uncoupler, produced a considerable membrane depolarization in the dark-adapted cells and a complete suppression of the light-induced hyperpolarization. Although 3-(3',4'-dichlorophenyl)-1,1-dimethylurea (DCMU), an inhibitor of photosynthetic electron transport, did not affect the membrane potential in darkness, it completely inhibited the light-induced membrane hyperpolarization. In vivo illumination of the leaves with red light caused a substantial decrease in the Km for ATP, not only of the vanadate-sensitive ATP-hydrolyzing activity in leaf homogenate, but also of the ATP-dependent H+-transporting activity in plasma membrane (PM) vesicles isolated from the leaves by aqueous polymer two-phase partitioning methods. The effects of red light were negated by the presence of DCMU during illumination. In vivo illumination with far-red light had no effect on the Km for ATP of H+-transporting activity. These results strongly suggest that an electrogenic component in the membrane potential of the mesophyll cell is generated by the PM H+-ATPase, and that photosynthesis-dependent modulation of the enzymatic activity of the PM H+-ATPase is involved in the light-induced membrane hyperpolarization.
authors.affiliation: Department of Biology, Graduate School of Science, Osaka University, Toyonaka 560-0043, Japan. aharada8@bio.sci.osaka-u.ac.jp
authors.forename: Akiko
authors.initials: A
authors.lastname: Harada
authors.forename: Yoshiji
authors.initials: Y
authors.lastname: Okazaki
authors.forename: Shingo
authors.initials: S
authors.lastname: Takagi
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000031:analogs & derivatives* / Q000494:pharmacology; D002462:Cell Membrane / Q000201:enzymology / Q000528:radiation effects; D004024:Dicyclohexylcarbodiimide / Q000494:pharmacology; D004237:Diuron / Q000494:pharmacology; D006859:Hydrogen / Q000378:metabolism; D007700:Kinetics; D008027:Light; D019684:Magnoliopsida / Q000201:enzymology / Q000502:physiology / Q000528:radiation effects*; D008564:Membrane Potentials / Q000187:drug effects / Q000528:radiation effects; D010788:Photosynthesis / Q000502:physiology / Q000528:radiation effects*; D010936:Plant Extracts / Q000378:metabolism / Q000528:radiation effects; D018515:Plant Leaves / Q000201:enzymology / Q000502:physiology / Q000528:radiation effects*; D006180:Proton-Translocating ATPases / Q000378:metabolism*
chemical_list: D010936:Plant Extracts; D004024:Dicyclohexylcarbodiimide; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D006859:Hydrogen; D000255:Adenosine Triphosphate; D004237:Diuron; D006180:Proton-Translocating ATPases