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, subclass II and III SnRK2s were shown to play crucial roles in ABA signaling or osmotic stress responses. In this study, we studied in planta functions of the subclass I SnRK2s (SRK2A/SnRK2.4, SRK2B/SnRK2.1, SRK2G/SnRK2.1, SRK2H/SnRK2.5) in Arabidopsis. To analyze their functions, we established the srk2abgh quadruple knockout mutant with some growth retardation. Microarray analysis showed that the many pathogen or salicylic acid (SA)-related genes were up-regulated in srk2abgh under drought stress conditions. However, endogenous SA was not changed in srk2abgh, but JA-IIe was decreased to less than half of wild-type plants. Our results suggest that some antagonistic relations between SA and JA were inhibited in srk2abgh under drought stress condition. In other words, subclass I SnRK2s might be involved in negative regulation of SA-responsive genes under drought stress via JA pathway.
