CARK6 is involved in abscisic acid to regulate stress responses in Arabidopsis thaliana.

Abscisic acid (ABA), one of phytohormones, is induced in response to abiotic stress to mediate plant acclimation to environmental challenge. Key players of the ABA-signaling pathway are the ABA-binding receptors (RCAR/PYR1/PYL), which perceive ABA and then inhibit PP2Cs to activate SnRK2s. Here, we report that a putative receptor-like cytoplasmic kinase (RLCK) in Arabidopsis named CARK6, which is a member of cytosolic ABA receptor kinases. We confirm that CARK6 interacts with ABA receptors, RCAR11-14 in vitro and in vivo. Induced overexpression of CARK6 in Arabidopsis enhances sensitivity to ABA by inhibition of seed germination and root elongation, and promotes the drought resistance. However, loss-of-function seedlings of cark6 are less sensitive to ABA and show reduced drought stress response with respect to water loss and stomatal aperture. In transgenic Arabidopsis complementation lines in the cark6 mutant background, stress responsivity was restored by CARK6. In conclusion, our data provide evidence that CARK6 plays a positive role in ABA signaling in Arabidopsis.