OsVPS16 Deficiency Enhances Salinity Tolerance in Rice by Regulating Ion Homeostasis, Antioxidant Activity, and Stress-Responsive Gene Expression

Soil salinization has emerged as a significant global threat to agricultural productivity. Rice is susceptible to salinity stress at the seedling stage. However, the mechanisms underlying rice responses to salinity stress remain incompletely characterized. In this study, we have characterized a transfer DNA (T-DNA) insertion mutant line of rice, designated OsVPS16 (Os12g0594200), to elucidate its functional role in salt stress tolerance. A real-time quantitative PCR (RT-qPCR) analysis revealed that salt stress inhibited the expression of OsVPS16, with the vps16 mutant showing negligible expression levels. A phenotypic analysis showed that the loss of OsVPS16 enhanced primary root elongation, and increased the survival rate to improve salt stress tolerance. Compared to the wild type (DJ), the vps16 mutant accumulated less Na+ and more K+ in the shoots under salt stress. Furthermore, the vps16 mutant displayed decreased malondialdehyde (MDA) accumulation and enhanced the activities of superoxide dismutase (SOD) and peroxidase (POD) under salt stress. Transcriptomic profiling identified 1236 differentially expressed genes (DEGs) between vps16 and DJ roots under salt stress. A functional enrichment analysis revealed that DEGs were enriched in protein serine/threonine kinase activity, Ca2+ signal pathways, and the MAPK signaling pathway. Notably, the up-regulation of critical protein kinases (PKs) and transcription factors (TFs), including OsSRK1, OsCDPK21, and OsNAC45, probably adds to the effect of OsVPS16 mutation to account for salt stress tolerance. Collectively, comprehensive physiological and molecular analyses demonstrated that the loss of OsVPS16 improves rice salt tolerance through multiple mechanisms, including the regulation of K+/Na+ homeostasis, the modulation of antioxidant enzyme activities, and the transcriptional reprogramming of stress-responsive genes. This study not only elucidates the function of a novel salt stress response gene in rice, but also provides valuable genetic resources for developing salt-tolerant rice cultivars through molecular breeding approaches.