Abstract
Overexpression of PKABA1, a wheat ABA inducible Protein kinase(PK), has been shown to suppress the GA-induced promoter activity of α-amylase, suggesting that PKABA1 functions in the ABA-modulation of GA signaling. Guard cell-specific ABA-activated PK(AAPK), which control stomatal pores, has been shown to regulate plasma membrane ion channels. Both PKABA1 and AAPK belong to SnRK2 PK family. However, the functions of these PKs in ABA signaling pathway is still unclear. There are 10 members of SnRK2 family in the rice genome. We report here the expression and function of the ten rice SnRk2 members, designated SAPK(Stress and/or ABA regulated PK) 1 to 10. Transient expression of affinity and epitope-tagged SAPK1 to 10 revealed that all of these kinases are activated by osmotic stress. Three of these members are also activated by ABA treatment. These results suggest that rice SAPK family members are involved in both ABA and osmotic stress signaling cascades.
