Molecular Evolution and Stress and Phytohormone Responsiveness of Genes in .

Sucrose transporters (SUTs) play key roles in allocating the translocation of assimilates from source to sink tissues. Although the characteristics and biological roles of have been intensively investigated in higher plants, this gene family has not been functionally characterized in cotton. In this study, we performed a comprehensive analysis of genes in the tetraploid cotton . A total of 18 genes were identified and classified into three groups based on their evolutionary relationships. Up to eight genes in were placed in the dicot-specific SUT1 group, while four and six genes were, respectively, clustered into SUT4 and SUT2 groups together with members from both dicot and monocot species. The genes within the same group displayed similar exon/intron characteristics, and homologous genes in At and Dt subgenomes, , and exhibited one-to-one relationships. Additionally, the duplicated genes in the diploid and polyploid cotton species have evolved through purifying selection, suggesting the strong conservation of loci in these species. Expression analysis in different tissues indicated that genes might play significant roles in cotton fiber elongation. Moreover, analyses of -acting regulatory elements in promoter regions and expression profiling under different abiotic stress and exogenous phytohormone treatments implied that genes, especially , might participate in plant responses to diverse abiotic stresses and phytohormones. Our findings provide valuable information for future studies on the evolution and function of genes in cotton.