Abstract:
Plant calcium-dependent protein kinases (CDPKs) may function as calcium sensors and play important roles in the regulation
of plant growth and development and in plant responses to biotic and abiotic stresses. The Arabidopsis (Arabidopsis thaliana)
genome encodes 34 CDPKs, and most of them have not been functionally characterized. Here, we report the functional
characterization of CPK10 in Arabidopsis response to drought stress. The cpk10 mutant, a T-DNA insertion mutant for the
Arabidopsis CPK10 gene, showed a much more sensitive phenotype to drought stress compared with wild-type plants, while
the CPK10 overexpression lines displayed enhanced tolerance to drought stress. Induction of stomatal closure and inhibition of
stomatal opening by abscisic acid (ABA) and Ca2+ were impaired in the cpk10 mutants. Using yeast two-hybrid methods, a heat
shock protein, HSP1, was identified as a CPK10-interacting protein. The interaction between CPK10 and HSP1 was further
confirmed by pull-down and bimolecular fluorescence complementation assays. The HSP1 knockout mutant (hsp1) plants
showed a similar sensitive phenotype under drought stress as the cpk10 mutant plants and were similarly less sensitive to ABA
and Ca2+ in regulation of stomatal movements. Electrophysiological experiments showed that ABA and Ca2+ inhibition of the
inward K+ currents in stomatal guard cells were impaired in the cpk10 and hsp1 mutants. All presented data demonstrate that
CPK10, possibly by interacting with HSP1, plays important roles in ABA- and Ca2+-mediated regulation of stomatal movements
