Genome-wide identification and expression analysis of the expansin gene family in Brassica napus L

Expansins (EXPs) are a class of proteins that cause the relaxation of plant cell walls, thereby playing a role in regulating cell growth and various developmental processes in plants. In this study, a comprehensive analysis of the EXP gene family in Brassica napus L. (B. napus) was conducted, 127 EXP genes of B. napus identified using the ZS11 reference genome. These genes were classified into four subfamilies: alpha-expansin (EXPA), beta-expansin (EXPB), expansin-like A (EXLA), and expansin-like B (EXLB), with 98, 18, 5, and 6 members, respectively, evenly distributed across 19 chromosomes. The physicochemical properties, motif structures, and chromosomal distribution of these genes were evaluated. Evolutionary analysis within and between genomes indicated that the EXP genes(BnaEXs) exhibit a high degree of conservation., and segmental duplication was identified as the primary driver of the expansion of the BnaEXs in B. napus. Additionally, synteny analysis between B. napus, Arabidopsis thaliana L. and Nicotiana tabacum L. revealed that BnaEXs exhibit diverse evolutionary patterns across different plant species. The gene expression levels of the B. napus transcriptome database (BnPIR) demonstrated that most members are expressed in at least one tissue of B. napus. The differential expression of eight BnaEXs in response to various stress conditions and across different tissues was demonstrated by qPCR. The results of this study provide a solid foundation for further elucidating the biological functions of expansin genes in B. napus development and offer valuable genetic resources for future crop improvement.