Abstract
Background
SWEET (Sugar Will Eventually be Exported Transporter) gene family is a unique type of sugar transporter, that plays a vital role in metabolic regulation, growth, development, and stress response in multiple species. This study aimed to systematically identify the SWEET gene family members and detect the regulation of gene expression and potential roles of the SWEET gene family in Brassica juncea.
Results
A total of 66 BjSWEET genes distributed across 17 chromosomes, were identified, and the gene structure and motifs were relatively conserved, with all members containing the MtN3/saliva domain. Phylogenetic analysis revealed that the SWEET gene family could be classified into four subfamilies (Clades I, II, III, and IV). Collinearity analysis showed that there were 118 pairs of segment duplicates, indicating that some BjSWEET genes were probably obtained by segmental duplication. The promoter region of the BjSWEET genes contained a large number of plant hormone-related response elements, stress-related response elements, growth and development elements, and light-responsive regulatory elements. Furthermore, analysis of the expression profiles revealed that the expression levels of the BjSWEET genes differed among the eight different tissues. qRT-PCR analysis of six selected BjSWEET genes revealed that the expression levels of BjSWEET17.2、BjSWEET17.4、BjSWEET12.2 and BjSWEET12.3 were significantly up-regulated under drought treatment, suggesting that these genes may respond to drought stress in Brassica juncea.
Conclusion
This study systematically identified and analyzed the SWEET gene family members in B. juncea for the first time, which lays the foundation for further research on the molecular mechanisms of drought resistance in B. juncea and provides theoretical guidance for the application of these genes in other species.