Phosphorylation of DUF1639 protein by osmotic stress/ABA-activated protein kinase 10 regulates abscisic acid-induced antioxidant defense in rice

Abstract

In rice (Oryza Sativa), Osmotic Stress/ABA-activated Protein Kinase 10 (SAPK10) has been shown to be induced by hyperosmotic stress and abscisic acid (ABA). However, the molecular function of SAPK10 and its downstream targets in ABA-induced antioxidant defense is poorly understood. Here, we identified an unknown function DUF1639 family protein, OsDUF1639.1, which interacts with SAPK10 in vitro and in vivo. OsDUF1639.1 positively regulates ABA responses in seed germination and tolerance to drought stress. We found that SAPK10 directly phosphorylates OsDUF1639.1 at Thr-80 in vitro. The transient expression analysis in combination with mutant analysis in rice protoplasts showed that Thr-80 is essential for ABA-induced stimulation of antioxidant defense by SAPK10. These results suggest that SAPK10 functions upstream of OsDUF1639.1 to regulate the activities of antioxidant enzymes, and Thr-80 phosphorylation of OsDUF1639.1 has a crucial role in ABA-induced antioxidant defense.