Protein phosphatase 1 positively regulates stomatal opening in response to blue light in Vicia faba.
Phototropins, plant blue light receptors, mediate stomatal opening through the activation of the plasma membrane H(+)-ATPase by unknown mechanisms. Here we report that type 1 protein phosphatase (PP1) positively regulates the blue light signaling between phototropins and the H(+)-ATPase in guard cells of Vicia faba. We cloned the four catalytic subunits of PP1 (PP1c) from guard cells and determined the expression of the isoforms in various tissues. Transformation of Vicia guard cells with PP1c isoforms that had lost enzymatic activity by one amino acid mutation, or with human inhibitor-2, a specific inhibitor protein of PP1c, suppressed blue light-induced stomatal opening. Addition of fusicoccin, an activator of the plasma membrane H(+)-ATPase, to these transformed guard cells induced normal stomatal opening, suggesting that the transformations did not affect the basic mechanisms for stomatal opening. Tautomycin, an inhibitor of PP1, inhibited blue light-induced H(+) pumping, phosphorylation of the plasma membrane H(+)-ATPase in guard cell protoplasts, and stomatal opening. However, tautomycin did not inhibit the blue light-dependent phosphorylation of phototropins. We conclude that PP1 functions downstream of phototropins and upstream of the H(+)-ATPase in the blue light signaling pathway of guard cells.
Takemiya
Atsushi
A
*Department of Biology, Faculty of Science, Kyushu University, Ropponmatsu, Fukuoka 810-8560, Japan.
Kinoshita
Toshinori
T
Asanuma
Miwako
M
Shimazaki
Ken-Ichiro
K
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D018506:Gene Expression Regulation, Plant; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008027:Light; D008969:Molecular Sequence Data; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D010766:Phosphorylation; D018524:Phototropism / Q000502:physiology*; D018515:Plant Leaves / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects; D054645:Protein Phosphatase 1; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism / Q000528:radiation effects; D017386:Sequence Homology, Amino Acid; D031307:Vicia faba / Q000166:cytology / Q000378:metabolism* / Q000528:radiation effects
D007527:Isoenzymes; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D006180:Proton-Translocating ATPases