OsDi19-1 Acts Downstream of OsABI5 to Negatively Regulate ABA-Inhibited Seed Germination and Seedling Growth in Rice

Seed germination and post-germination seedling growth are critical agronomic traits in the growth process of rice, determining the seedling emergence rate and seedling quality. Previous studies have indicated that members of the Di19 (Drought-induced 19) gene family are involved in the regulation of abscisic acid (ABA)-mediated seed germination and seedling growth. However, the roles of most members and their molecular connections with ABA signaling are not well understood in rice. Here, we found that the osdi19-1 mutant exhibits enhanced ABA sensitivity during seed germination and seedling growth compared to the wild type. The expression of OsDi19-1 was induced by multiple abiotic stresses and functions as a transcription activator, localized in both the cytoplasm and nucleus. We also found that OsDi19-1 regulates the expression of ABA signaling pathway genes during seed germination, without affecting ABA biosynthesis. Furthermore, the expression of OsDi19-1 was repressed in the aba insensitive 5 (osabi5) mutants under ABA treatment, and OsABI5 could bind to the promoter of OsDi19-1 and activated its expression. Taken together, our findings demonstrate that OsDi19-1 acts downstream of OsABI5 to negatively regulate ABA-inhibited seed germination and seedling growth, thereby establishing the molecular link between the core ABA signaling pathway and the Di19 family.