ZmSnRK2.8 responds to ABA through the SnRK2-PP2C complex.

Understanding the responses of maize to abscisic acid (ABA) dependent drought tolerance is an important topic for the biotechnological application of functional mechanisms of stress adaptation. Key components that control and modulate stress adaptive pathways include SnRK2 (sucrose non-fermenting 1-related protein kinases 2) proteins. Recent studies indicate that SnRK2 are plant specific kinases that together with ABA ligand PYR/PYL/RCAR proteins and type 2C group A protein phosphatases constitute the central core of abscisic acid perception and signal transduction. Here, we study drought responses in maize by analyzing the mechanism of ZmSnRK2.8 in ABA signaling to establish relevant analogies with other plant species. ZmSnRK2.8 is a very closely related protein to Arabidopsis OST1 (open stomata 1) kinase with nuclear and cytosolic subcellular localization able to auto-phosphorylate S182 or T183 amino acids on its activation loop suggesting that phosphorylation at these sites may be a general mechanism for SnRK2 activation. In addition, ZmSnRK2.8 is activated by ABA and interacts with PP2C phosphatases in a constitutive, ABA independent manner. Together, our data suggest a conserved mechanism of plant responses to ABA and drought stress in maize and point to the potential use of this kinase in improving programs of drought tolerance in crops.