title: Phosphorylation of plasma membrane aquaporin regulates temperature-dependent opening of tulip petals.
abstract: The opening and closing of tulip petals was reproduced in the dark by changing the temperature from 5 degrees C to 20 degrees C for opening and 20 degrees C to 5 degrees C for closing. The opening process was accompanied by (3)H(2)O transport through the stem from the incubation medium to the petals. A Ca(2+)-channel blocker and a Ca(2+)-chelator inhibited petal opening and (3)H(2)O transport. Several proteins in the isolated plasma membrane fraction were phosphorylated in the presence of 25 micro M Ca(2+) at 20 degrees C. The 31-kDa protein that was phosphorylated, was suggested immunologically as the putative plasma membrane aquaporin (PM-AQP). This phosphorylated PM-AQP clearly reacted with the anti-phospho-Ser. In-gel assay revealed the presence of a 45-kDa Ca(2+)-dependent protein kinase in the isolated plasma membrane. Phosphorylation of the putative PM-AQP was thought to activate the water channel composed of PM-AQP. Dephosphorylation of the phosphorylated PM-AQP was also observed during petal closing at 5 degrees C, suggesting the inactivation of the water channel.
authors.affiliation: Faculty of Life and Environmental Sciences, Shimane University, Matsue, Shimane, 690-8504 Japan.
authors.forename: Abul Kalam
authors.initials: AK
authors.lastname: Azad
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Sawa
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ishikawa
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Shibata
mesh_terms: D020346:Aquaporins / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D002614:Chelating Agents / Q000494:pharmacology; D035264:Flowers / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D019441:Plant Epidermis / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D013696:Temperature; D031447:Tulipa / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D014867:Water / Q000378:metabolism
chemical_list: D020346:Aquaporins; D002121:Calcium Channel Blockers; D002614:Chelating Agents; D014867:Water; D002118:Calcium