Genome-wide analysis of the CesA gene family in Brassica napus under abiotic stress and functional study of in root growth

Cellulose synthase is involved in complex biological processes, including the formation of primary and secondary cell walls, hormone signaling, and responses to environmental stresses. However, systematic identification and characterization of its gene family in the genus Brassica remain at an early stage. Heren, the cellulose synthase (CesA) gene family in Brassica napus (BnCesA) was systematically identified and characterized. Our analysis revealed that BnCesA genes are unevenly distributed across all 12 chromosomes and exhibit high sequence conservation with their orthologs in Brassica rapa and Brassica oleracea. Phylogenetic classification grouped the BnCesA genes into three distinct subfamilies, with subfamily III clustering closely with CesA genes from Arabidopsis thaliana and Oryza sativa. Cis-regulatory element analysis identified multiple stress-responsive motifs in BnCesA promoters. Tissue-specific expression profiling demonstrated that this gene family is predominantly expressed in the stem cortex and developing seeds. Notably, salt and osmotic stress treatments significantly upregulated the expression of BnCesA15 and its functionally associated genes. Haplotype analysis further revealed that specific BnCesA1 haplotypes were significantly correlated with enhanced root elongation under salt stress. Using ACT7 (the most stable internal reference gene) for normalization, RT-qPCR validation of nine representative BnCesA genes confirmed that BnCesA15, BnCesA21, and BnCesA24 exhibited strong and consistent regulatory trends across four stress conditions at multiple time points. Subcellular localization experiments indicated that BnCesA15 primarily localizes to the plasma membrane. This study provides novel insights into the molecular mechanisms underlying stress adaptation in B. napus and identifies candidate target genes for improving stress resistance in rapeseed breeding. Functional analysis revealed that mutation of AtCESA6 (corresponding to BnCesA15 in rapeseed) significantly affected root growth in Arabidopsis, resulting in much shorter roots compared with the wild type.