Abstract:
Drought is a major threat for plant growth and productivity. Plants lose over 90% of water by transpiration
through stomatal pores. The cytosolic free Ca2+ elevated in guard cells in response to stress stimuli triggers
stomatal closure. The plant-specific calcium-dependent protein kinases (CDPKs) play important roles in regulat ing downstream components of calcium signaling. In this study the biological function of Arabidopsis calcium dependent protein kinase, CPK8, in response to ABA signaling in guard cells was characterized. The plants of T DNA insertion mutant of cpk8 were more sensitive to drought stress than wild-type plants. The GUS staining stud ies confirmed that CPK8 expressed in leaves, specifically in guard cells. RT-PCR analysis showed that CPK8 ex pression was induced in response to drought stress. Further, pre-opened cpk8 stomata failed to close in response to
H2O2 and Ca2+, which is consistent with the inability of cpk8 plants to reduce water loss upon drought. The
drought susceptibility and stomatal impairment in response to H2O2 and Ca2+ of the cpk8 implicated that CPK8
plays a role in cellular environment in the control of H2O2 homeostasis and also as a compulsory molecule in the
transduction of H2O2 signal in guard cells in response to drought stress.
