The rice GLYCINE-RICH PROTEIN 3 enhances nitrogen utilization via mRNA stabilization of nitrogen transporter and assimilation genes

Efficient nitrogen utilization is crucial for sustainable crop productivity; however, the molecular regulators of nitrogen use efficiency (NUE) in rice remain incompletely understood. Here, we identify the GLYCINE-RICH RNA-BINDING PROTEIN (OsGRP3) as a positive regulator of NUE in rice through its role in post-transcriptional mRNA stabilization. Transgenic field trials revealed that OsGRP3 overexpression (OE) enhances agronomic performance under both normal and nitrogen-deficient conditions, with OE lines exhibiting increased plant height, seed number, and grain yield, particularly under low nitrogen input. In contrast, OsGRP3 knockdown (KD) plants displayed markedly reduced growth and yield. Molecular analyses demonstrated that OsGRP3 promotes the expression of key nitrogen uptake and assimilation genes, including OsAMT1.1 and OsGS1.1. RNA immunoprecipitation and decay assays confirmed that OsGRP3 directly binds to and stabilizes these transcripts under nitrogen-limited conditions. Enhanced ammonium uptake and elevated amino acid accumulation in OE lines further supported OsGRP3's role in facilitating nitrogen assimilation. These findings suggest that OsGRP3 binds to and stabilizes nitrogen-related transcripts, thereby promoting their expression during nutrient stress. Overall, our study reveals OsGRP3 as a crucial post-transcriptional regulator of NUE in rice, providing a mechanistic framework for its function. Targeted manipulation of OsGRP3 expression may offer a promising strategy for improving nitrogen utilization and crop yield under suboptimal fertilizer conditions.