Deciphering OsCBS gene family in rice: evolution, subcellular localization, and response to salt stress

Abstract Cystathionine β-synthase (CBS) plays crucial roles in abiotic stress responses. However, the molecular characteristics of the OsCBS gene family in rice and its transcriptional response to salt stress remain poorly characterized. This study systematically identified 28 OsCBS genes in the rice genome, unevenly distributed on nine chromosomes. Collinearity analysis revealed three segmental duplication pairs ( OsCBS5 - OsCBS24 , OsCBS 6- OsCBS19 , and OsCBS27 - OsCBS28 ), indicating that segmental duplication is a major force driving family expansion. Gene structure and conserved motif analyses showed that the exon numbers varied among family members, but the core conserved motifs were consistently present. Promoter regions contained numerous cis-acting elements associated with hormone and abiotic stress responsiveness, including salt stress. Quantitative real-time PCR (qRT-PCR) demonstrated that salt stress significantly induced OsCBS genes. Notably, OsCBS13 and OsCBS25 were upregulated in roots, OsCBS6 and OsCBS7 in shoots, and OsCBS3 and OsCBS11 in both tissues. Subcellular localization revealed specific tonoplast targeting of OsCBS11 and dual chloroplast–plasma membrane localization of OsCBS13. This systematic characterization of the OsCBS gene family and its expression patterns under salt stress provides a valuable reference for further functional studies of OsCBS in rice salt tolerance.