OsDi19-4 acts downstream of OsCDPK14 to positively regulate ABA response in rice

The drought-induced 19 protein family consists of several atypical Cys2/His2-type zinc finger proteins in plants and plays an important role in abiotic stress. In this study, we found that overexpressing OsDi19-4 in rice altered the expression of a series of abscisic acid (ABA)-responsive genes, resulting in strong ABA-hypersensitive phenotypes including ABA-induced seed germination inhibition, early seedling growth inhibition and stomatal closure. On the contrary, OsDi19-4 knockdown lines were less sensitive to ABA. Additionally, OsCDPK14 was identified to interact with OsDi19-4 and be responsible for the phosphorylation of OsDi19-4, and the phosphorylation of OsDi19-4 was further enhanced after the treatment of ABA. Apart from these, OsDi19-4 was shown to directly bind to the promoters of OsASPG1 and OsNAC18 genes, two ABA-responsive genes, and regulate their expression. Transient expression assays confirmed the direct regulation role of OsDi19-4, and the regulation was further enhanced by the increased phosphorylation of OsDi19-4 after the treatment of ABA. Taken together, these data demonstrate that OsDi19-4 acts downstream of OsCDPK14 to positively regulate ABA response by modulating the expression of ABA-responsive genes in rice.