Journal Article

Phosphorylation of Plasma Membrane Aquaporin Regulates Temperature-Dependent Opening of Tulip Petals

Abul Kalam Azad, Yoshihiro Sawa, Takahiro Ishikawa and Hitoshi Shibata

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 45, issue 5, pages 608-617
Published in print May 2004 | ISSN: 0032-0781
Published online May 2004 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pch069
Phosphorylation of Plasma Membrane Aquaporin Regulates Temperature-Dependent Opening of Tulip Petals

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  • Plant Sciences and Forestry

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The opening and closing of tulip petals was reproduced in the dark by changing the temperature from 5°C to 20°C for opening and 20°C to 5°C for closing. The opening process was accompanied by 3H2O transport through the stem from the incubation medium to the petals. A Ca2+-channel blocker and a Ca2+-chelator inhibited petal opening and 3H2O transport. Several proteins in the isolated plasma membrane fraction were phosphorylated in the presence of 25 µM Ca2+ at 20°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 Ca2+-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°C, suggesting the inactivation of the water channel.

Keywords: Keywords: Ca2+ — CDPK — Dephosphorylation — Petal oscillation — Phosphorylation — Water transport.; Abbreviations: AQP, aquaporins; BAPTA, O,O′-bis(2-aminophenyl)ethylene-glycol-N,N,N′,N′-tetraacetic acid; [Ca2+]cyt, cytosolic free Ca2+ concentration; CDPK, Ca2+-dependent protein kinase; KP, potassium phosphate; MBP, myelin basic protein; 2-ME, 2-mercaptoethanol; PM, plasma membrane; PM-AQP, plasma membrane aquaporin; RR, ruthenium red; TCA, trichloroacetic acid.

Journal Article.  7124 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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