Poster: Stomatal Physiology

Abs # 388: Involvement of a serine/threonine protein phosphatase in blue light signaling of stomatal guard cells

Presenter:	Takemiya, Atsushi , takemiyarcb@mbox.nc.kyushu-u.ac.jp
Authors	Takemiya, Atsushi  (A)   Kinoshita, Toshinori  (A)   Shimazaki, Ken-ichiro  (A)
Affiliations:	(A): Department of Biology, Faculty of Science, Kyushu University

Blue light (BL) perceived by phototropins (phots), BL receptors in guard cells, induces stomatal opening through the activation of plasma membrane H⁺-ATPase. Recent pharmacological evidence suggested that protein phosphatase might be involved in BL signal transduction in guard cells. In this study, we used tautomycin (TAU), a specific inhibitor of type1 serine/threonine protein phosphatase, to investigate the role of protein phosphatase in BL signaling. In the presence of TAU, both BL-induced stomatal opening and H⁺ pumping were inhibited. In accord with this, the H⁺-ATPase was not phosphorylated, but phots were phosphorylated in the presence of TAU in response to BL. These results indicate that a protein phosphatase is involved downstream of phots and upstream of H⁺-ATPase in BL signaling of guard cells, and that the protein phosphatase transmits BL signal to the plasma membrane H⁺-ATPase for its activation. Determination of the activity of intracellular protein phosphatase is now in progress.