title: Identification of a regulatory subunit of protein phosphatase 1 which mediates blue light signaling for stomatal opening.
abstract: Protein phosphatase 1 (PP1) is a eukaryotic serine/threonine protein phosphatase comprised of a catalytic subunit (PP1c) and a regulatory subunit that modulates catalytic activity, subcellular localization and substrate specificity. PP1c positively regulates stomatal opening through blue light signaling between phototropins and the plasma membrane H(+)-ATPase in guard cells. However, the regulatory subunit functioning in this process is unknown. We identified Arabidopsis PRSL1 (PP1 regulatory subunit2-like protein1) as a regulatory subunit of PP1c. Tautomycin, a selective inhibitor of PP1c, inhibited blue light responses of stomata in the single mutants phot1 and phot2, supporting the idea that signals from phot1 and phot2 converge on PP1c. We obtained PRSL1 based on the sequence similarity to Vicia faba PRS2, a PP1c-binding protein isolated by a yeast two-hybrid screen. PRSL1 bound to Arabidopsis PP1c through its RVxF motif, a consensus PP1c-binding sequence. Arabidopsis prsl1 mutants were impaired in blue light-dependent stomatal opening, H(+) pumping and phosphorylation of the H(+)-ATPase, but showed normal phototropin activities. PRSL1 complemented the prsl1 phenotype, but not if the protein carried a mutation in the RVxF motif, suggesting that PRSL1 functions through binding PP1c via the RVxF motif. PRSL1 did not affect the catalytic activity of Arabidopsis PP1c but it stimulated the localization of PP1c in the cytoplasm. We conclude that PRSL1 functions as a regulatory subunit of PP1 and regulates blue light signaling in stomata.
authors.affiliation: Department of Biology, Faculty of Science, Kyushu University, 6-10-1 Hakozaki, Fukuoka, 812-8581 Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Takemiya
authors.forename: Shota
authors.initials: S
authors.lastname: Yamauchi
authors.forename: Takayuki
authors.initials: T
authors.lastname: Yano
authors.forename: Chie
authors.initials: C
authors.lastname: Ariyoshi
authors.forename: Ken-ichiro
authors.initials: K
authors.lastname: Shimazaki
mesh_terms: D020816:Amino Acid Motifs; D017360:Arabidopsis / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D008027:Light; D008969:Molecular Sequence Data; D009154:Mutation; D010750:Phosphoproteins / Q000378:metabolism; D010802:Phylogeny; D054046:Plant Stomata / Q000502:physiology*; D030821:Plants, Genetically Modified; D054645:Protein Phosphatase 1 / Q000235:genetics* / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000378:metabolism; D011714:Pyrans / Q000494:pharmacology; D015398:Signal Transduction; D013141:Spiro Compounds / Q000494:pharmacology; D031307:Vicia faba / Q000737:chemistry
chemical_list: D029681:Arabidopsis Proteins; C423903:PHOT2 protein, Arabidopsis; D010750:Phosphoproteins; D021122:Protein Subunits; D011714:Pyrans; D013141:Spiro Compounds; C053079:tautomycin; C103646:NPH1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases; D054645:Protein Phosphatase 1; D006180:Proton-Translocating ATPases