CDPK may be an important component of Ca2+ signaling in stomata

 

 

Guard cells possess a calcium-dependent protein kinase that phosphorylates the KAT1 potassium channel

by Li J., Lee Y. R., Assmann S. M. (1998)

Jiaxu Li, Mississippi State University, Starkville, USA

Yuh-Ru Julie Lee,

Sarah M. Assmann, Pennsylvania State University, USA

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in Plant Physiol 116: 785–795 -DOI: https://doi.org/10.1104/pp.116.2.785 – 

Abstract/FREE Full Text – 

http://www.plantphysiol.org/content/116/2/785

Abstract

Increasing evidence suggests that changes in cytosolic Ca²⁺ levels and phosphorylation play important roles in the regulation of stomatal aperture and as ion transporters of guard cells. However, protein kinases responsible for Ca²⁺ signaling in guard cells remain to be identified.

Using biochemical approaches, we have identified a Ca²⁺-dependent protein kinase with a calmodulin-like domain (CDPK) in guard cell protoplasts of Vicia faba. Both autophosphorylation and catalytic activity of CDPK are Ca²⁺dependent. CDPK exhibits a Ca²⁺-induced electrophoretic mobility shift and its Ca²⁺-dependent catalytic activity can be inhibited by the calmodulin antagonists trifluoperazine andN-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide.

Antibodies to soybean CDPKα cross-react with CDPK. Micromolar Ca²⁺concentrations stimulate phosphorylation of several proteins from guard cells; cyclosporin A, a specific inhibitor of the Ca²⁺-dependent protein phosphatase calcineurin enhances the Ca²⁺-dependent phosphorylation of several soluble proteins. CDPK from guard cells phosphorylates the K⁺channel KAT1 protein in a Ca²⁺-dependent manner.

These results suggest that CDPK may be an important component of Ca²⁺ signaling in guard cells.