Disruption of OsGPRP3 impairs salt tolerance and growth vigor in rice

Soil salinization poses a major threat to global rice production, underscoring the need to identify key genetic components of salt tolerance. Glycine- and proline-rich proteins (GPRPs) are evolutionarily conserved across plant species, yet their roles in crop salinity responses remain poorly understood. Here, we demonstrate that disruption of OsGPRP3, a GPRP gene previously associated with grain development, markedly impairs salt tolerance and growth vigor in rice throughout its life cycle, from germination to maturity. CRISPR-Cas9-generated OsGPRP3 knockout lines exhibited heightened salt sensitivity, with germination and seedling survival rates reduced to 6.7-14.4 % and 38.9-66.7 %, respectively, compared to 58.9 % and 88.5 % in wild-type ZH11. Under reproductive-stage salt stress, grain yield per plant declined by 24.8 % in mutant versus only 9.1 % in ZH11. Physiological assays revealed greater H₂O₂ accumulation, reduced SOD and CAT activities, and lower proline levels in mutants, indicating impaired oxidative and osmotic homeostasis. Transcriptomic profiling identified 998 differentially expressed genes, including 324 mutant-specific salt-responsive genes enriched in pathways related to ion transport, phenylpropanoid biosynthesis, and tryptophan metabolism-key processes suggesting potential disruptions in ionic balance, cell wall remodeling, and auxin-mediated growth regulation. Collectively, our findings demonstrate that OsGPRP3 plays a pivotal role in coordinating physiological and molecular responses to salt stress in rice. This study provides the first functional evidence linking a GPRP family member to multi-stage salinity adaptation in crops, and offers promising genetic targets for the development of salt-resilient rice varieties.