The OsDREB1C-OsNAC3-OsGH3.2 module regulates seed germination in rice

Abstract Seed germination is a critical determinant for successful direct-seeding cultivation in rice (Oryza sativa); however, its underlying regulatory mechanisms remain poorly understood. Here, we reveal a transcriptional cascade involving OsDREB1C-OsNAC3-OsGH3.2 that modulates seed germination through an abscisic acid (ABA)-dependent auxin pathway. While exogenous indole-acetic acid (IAA) treatment did not significantly reduce seed germination of Osnac3 mutants compared to the wild type (WT), a pronounced reduction in seed germination was observed in Osnac3 mutants when IAA was applied in the presence of ABA. OsNAC3 directly binds to the promoter of the auxin metabolism gene OsGH3.2, activating its expression and reducing IAA accumulation during early germination stages. Notably, natural variation in the OsNAC3 promoter alters the binding affinity of transcription factor OsDREB1C, which itself directly activates both OsNAC3 and OsGH3.2 expression. OsDREB1C and OsGH3.2 function as upstream and downstream regulators of OsNAC3, respectively, both modulating seed germination through ABA-dependent auxin pathways. Targeted improvement of the OsDREB1C-OsNAC3-OsGH3.2 module provides a molecular breeding strategy to enhance rice adaptation to direct-seeding cultivation.