Molecular characterization of legume-lectin receptor-like kinase SIT genes in Brassica napus reveals the involvement of BnaA02.SIT3 in salt tolerance

Plant Legume-type lectin receptor-like kinases (L-LecRLKs) are widely regarded as key regulators of plant signaling networks that orchestrate diverse cellular and developmental processes in several species. Although vital for plant growth, development, and stress response, the landscape of L-LecRLK Brassica napus Salt Intolerance (BnaSIT) genes in Brassica napus (rapeseed) remains elusive. In this study, we conducted a genome-wide identification and discovered 21 BnaSIT genes unevenly distributed on 11 chromosomes. The BnaSIT gene family, comprising three subfamilies expanded by segmental duplication, encodes canonical L-LecRLKs localized to the plasma membrane. Structural and in vitro evidence confirms that these proteins contain functional kinase domains. Furthermore, their promoters are enriched with cis-regulatory elements associated with growth, hormonal, and stress responses, suggesting diverse physiological roles. This finding aligns with their expression profiles across different organs and their differential expression in response to hormone and stress stimuli. Overexpression of BnaA02.SIT3 enhanced salt tolerance in Arabidopsis thaliana. Thereby, these results demonstrate that BnaA02.SIT3 acts as an active protein kinase and may play important roles in regulating plant growth, development, and stress responses. Consequently, this study provides comprehensive genomic identification and characterization of rapeseed L-LecRLK BnaSITs. It thereby establishes a critical resource for future functional studies, which aim to elucidate the roles of these genes in growth and stress adaptation.