Abstract
SRK2C is one of SnRK2 protein kianses in Arabidopsis, and that is activated by hyper osmolarity and impact drought tolerance of Arabidopsis by controlling appropriate gene expression (Umezawa et al., PNAS, 2004). Here, we report that SRK2C activation is also elevated by exogenous ABA in Arabidopsis T87 cultured cells. We observed several differences between ABA-dependent and osmotic stress-dependent activation of SRK2C. First, osmotic stress-dependent activation of SRK2C was depleted by EGTA pretreatment for T87 cells, but EGTA did not affect ABA-dependent activation. Second, the immuno- precipitation of SRK2C from 32P-labeled cells showed that SRK2C is phosphorylated during osmotic stress-dependent activation, but not during ABA-dependent activation. These results suggest that the activation of SRK2C is regulated by different pathways between hyper osmolarity and ABA action. In addition, we will discuss about the relationship between SRK2C activation and ABA signaling in plants, referring some experimental data.
