Calcium-dependent protein kinase with the inward rectified guard cell K+ channel KAT1 and stomata

 

Co-expression of calcium-dependent protein kinase with the inward rectified guard cell K+ channel KAT1 alters current parameters in Xenopus laevis oocytes.

by Berkowitz G.Zhang X.Mercie R.Leng Q.Lawton M. (2000)

 

in Plant Cell Physiol 41: 785790 – DOI: https://doi.org/10.1093/pcp/41.6.785 – 

Abstract/FREE Full Text – 

https://academic.oup.com/pcp/article/41/6/785/1923323/Co-Expression-of-Calcium-Dependent-Protein-Kinase

Abstract

Increased guard cell cytosolic [Ca2+] is known to be involved in signal transduction pathways leading to stomatal closure, and inhibit the inward rectifying guard cell K+channel KAT1.

Guard cell calcium-dependent protein kinase (CDPK) has been shown to phosphorylate KAT1; such phosphorylation is known to modulate other K+ channels involved in signal transduction cascades.

The work reported here focused on demonstrating CDPK-dependent inhibition of KAT1 currents. A cDNA encoding soybean CDPK was generated and it’s translation product was shown to be functional; demonstrating Ca2+-dependent autophosphorylation and phosphorylation of a target protein. Ion currents were monitored using voltage clamp techniques upon expression of KAT1 in Xenopus laevis oocytes.

Co-expression of recombinant CDPK with KAT1 in oocytes altered the kinetics and magnitude of induced K+ currents; at a given hyperpolarizing command voltage, the magnitude of KAT1 currents was reduced and the half-time for channel activation was increased.

This finding supports a model of Ca2+-dependent ABA inhibition of inward K+ currents in guard cells as being mediated by CDPK phosphorylation of KAT1.

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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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