Protein phosphorylation is a prerequisite for intracellular Ca2+ release and ion channel control by nitric oxide and abscisic acid in guard cells
by Sokolovski S., Hill A., Gay R., Garcia-Mata C., Lamattina L., Blatt M. R. (2005)
Michael R. Blatt
in The Plant Journal2005;43:520-529. –
Recent work has indicated that nitric oxide (NO) and its synthesis are important elements of signal cascades in plant–pathogen defence, and are a prerequisite for drought and abscisic acid (ABA) responses in Arabidopsis thaliana and Vicia faba guard cells.
NO regulates inward-rectifying K+ channels and Cl− channels of Vicia guard cells via intracellular Ca2+ release. However, its integration with related signals, including the actions of serine–threonine protein kinases, is less well defined.
We report here that the elevation of cytosolic-free [Ca2+] ([Ca2+]i) mediated by NO in guard cells is reversibly inhibited by the broad-range protein kinase antagonists staurosporine and K252A, but not by the tyrosine kinase antagonist genistein.
The effects of kinase antagonism translate directly to a loss of NO-sensitivity of the inward-rectifying K+ channels and background (Cl− channel) current, and to a parallel loss in sensitivity of the K+ channels to ABA.
These results demonstrate that NO-dependent signals can be modulated through protein phosphorylation upstream of intracellular Ca2+ release, and they implicate a target for protein kinase control in ABA signalling that feeds into NO-dependent Ca2+ release.