Amino acid transporters of Brassica napus: Identification, evolution, expression and response to various stresses

Amino acid transporters (AATs) are membrane proteins that mediate the transport of amino acids and other compounds across membranes and have an important role in plant growth and development. However, to date, little evolutionary analysis of this gene family has been reported in Brassica napus. In this study, 191 AAT members were identified in B. napus. They were divided into 12 subfamilies based on phylogenetic relationships, and similar gene structures and conserved domains existed in each subfamily. These BnaAATs were unevenly distributed on 19 chromosomes, mainly through whole genome duplication (WGD) or segmental duplication events. Collinearity analysis of the AAT genes of B. napus with Arabidopsis, Brassica rapa and Brassica oleracea showed that the BnaAAT gene family had a large number of homologous genes with the diploid ancestor. The BnaAAT gene family had undergone strong purifying selection during evolution, but some positive selection sites had also been identified. Further studies of the cis-acting elements and their expression patterns of BnaAATs in different tissues and under stress, combined with quantitative real-time PCR (qRT-PCR) analysis, showed that BnaAATs were involved in growth regulation and various stress responses. Protein-protein network analysis also identified 442 interactions, implying that this gene family was functionally diverse. This study provides the first comprehensive survey of the BnaAAT gene family and lays the foundation for future functional validation.