Abstract
SNF1-related protein kinases 2 (SnRK2s) are activated by ABA- and/or osmotic stress and are involved in stress signaling pathways in plants. Ten members of Arabidopsis SnRK2 are classified into three subclasses. Recently, three subclass III SnRK2s including SRK2E/OST1/SnRK2.6 were shown to play crucial roles in ABA signal transduction pathways. However, the functions of other two subclasses of SnRK2s are still unclear. In this study, we studied in planta functions of the subclass II SnRK2s (SRK2C/SnRK2.8 and SRK2F/SnRK2.9) in Arabidopsis. To analyze their functions, we established the srk2cf double mutant. Microarray analysis showed that the many ABA-inducible genes were downregulated in srk2cf under drought stress conditions. However, those genes showed normal response to ABA even in srk2cf, suggesting that the subclass II SnRK2s mediate drought stress signaling significantly, but that their roles are only supportive in ABA-dependent pathway. We could not observe significant phenotypes of srk2cf. We will discuss the role of the subclass II SnRK2s in Arabidopsis.
