PP1 functions downstream of phototropins and upstream of the H(+)-ATPase in the blue light signaling pathway of stomata

Photo credit: PNAS

Response to fusicoccin of guard cells transformed with PP1c mutant and inhibitor-2. (A and C) Images of guard cells under bright field (a) and fluorescence conditions (b). Typical guard cells transformed with VfPP1c-1-H137N:sGFP (A) and inhibitor-2:sGFP (C) are shown. Epidermal strips were preincubated for 2.5 h in darkness before fusicoccin (10 μM) was added; images were taken after further incubation for 2.5 h in darkness. (Scale bars, 10 μm.) (B and D) Determination of half stomatal apertures of guard cells transformed with VfPP1c-1-H137N:sGFP (B) or inhibitor-2:sGFP (D). Data are means ± SE (n = 45, pooled from triplicate experiments).

Protein phosphatase 1 positively regulates stomatal opening in response to blue light in Vicia faba.

by Takemiya A., Kinoshita T., Asanuma M., Shimazaki K.-i. (2006)

*Department of Biology, Faculty of Science, Kyushu University, Ropponmatsu, Fukuoka 810-8560, Japan.

in Proceedings of the National Academy of Sciences, USA 2006;103:13549-13554. -DOI: 10.1073/pnas.0602503103 –

Abstract/FREE Full TextCASPubMedArticle

https://www.ncbi.nlm.nih.gov/pubmed/16938884?dopt=Abstract&holding=npg

vicia-faba-fl-nkramer
Vicia faba (broad vetch) – https://newfs.s3.amazonaws.com/taxon-images-1000s1000/Fabaceae/vicia-faba-fl-nkramer.jpg

Abstract

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.

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Published by

Willem Van Cotthem

Honorary Professor of Botany, University of Ghent (Belgium). Scientific Consultant for Desertification and Sustainable Development.

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