Fig. 1: SnRK2s downstream targets in osmotic stress signalling pathways.
From: Role of Raf-like kinases in SnRK2 activation and osmotic stress response in plants
Schematic cartoon of the downstream targets described for the different subclasses of SnRK2s. ABA-unresponsive subclass I SnRK2s are activated by phosphorylation under osmotic stress and activate components of the mRNA decapping complex VCS through direct phosphorylation. Subclass I SnRK2s also interact with PA and phosphorylate two dehydrin proteins, ERD10 and ERD14, in response to osmotic stress. ABA-responsive subclass II SnRK2s are activated by phosphorylation under osmotic stress and phosphorylate GLX1, 14-3-3, ADK1 and R5P target proteins. Subclass II SnRK2s likely activate AREB/ABF transcription factors in response to osmotic stress. Subclass III SnRK2s, the core components of ABA signalling, are activated by phosphorylation under osmotic stress and they phosphorylate AREB/ABF, which in turn activate the expression of stress-responsive genes. Subclass III SnRK2s also phosphorylate a number of substrates, including AKS1 transcription factors, BRM, SNS1, HYL1, and SE1 proteins and SLAC1, RBOHF, and KAT1 membrane proteins. PA, phosphatidic acid; VCS, VARICOSE; ERD, EARLY RESPONSIVE TO DEHYDRATION; GLX1, GLYOXALASE 1; ADK1, ADENOSINE KINASE 1; R5P, Ribose 5-phosphate isomerase; AKS1, ABA-RESPONSIVE KINASE SUBSTRATE 1; BRM, BRAHMA; SNS1, SNRK2-SUBSTRATE 1; HYL1, HYPONASTIC LEAVES; SE, SERRATE; MAPKKK, mitogen-activated protein kinase kinase kinases; SLAC, SLOW ANION CHANNEL-ASSOCIATED; A−, anions; KAT1, POTASSIUM CHANNEL IN ARABIDOPSIS THALIANA 1; K+, potassium; RBOHF, RESPIRATORY BURST OXIDASE HOMOLOG F. Straight arrows indicate direct interaction and phosphorylation, dashed arrows (black) indicate in vitro interactions not fully experimentally validated in vivo, and dashed arrows (grey) depict ion flux through membrane channel proteins.
