Two closely related subclass II SnRK2 protein kinases cooperatively regulate drought-inducible gene expression.

The subclass III group of SNF1-related protein kinase 2 (SnRK2) members is known to play an important role in ABA and osmotic stress signaling in Arabidopsis; however, the roles of other subclasses remain elusive. Here, we established a double mutant of SRK2C/SnR2.8 and SRK2F/SnRK2.7 to investigate the functions of subclass II SnRK2s. Microarray analysis suggested that subclass II SnRK2s regulate some drought-responsive genes involving ABA-responsive element binding transcription factors (AREB/ABF) and their targets, and quantitative reverse transcription- PCR confirmed that those genes were down-regulated significantly in srk2cf. This study indicates that subclass II SnRK2s also play important roles in drought stress signaling in Arabidopsis.