Genome-Wide Analysis of the UDP-Glycosyltransferase Family Reveals Its Roles in Coumarin Biosynthesis and Abiotic Stress in Melilotus albus

Abstract

Coumarins, natural products abundant in <i>Melilotus albus</i>, confer features in response to abiotic stresses, and are mainly present as glycoconjugates. UGTs (UDP-glycosyltransferases) are responsible for glycosylation modification of coumarins. However, information regarding the relationship between coumarin biosynthesis and stress-responsive <i>UGT</i>s remains limited. Here, a total of 189 <i>MaUGT</i> genes were identified from the <i>M. albus</i> genome, which were distributed differentially among its eight chromosomes. According to the phylogenetic relationship, <i>MaUGT</i>s can be classified into 13 major groups. Sixteen <i>MaUGT</i> genes were differentially expressed between genotypes of Ma46 (low coumarin content) and Ma49 (high coumarin content), suggesting that these genes are likely involved in coumarin biosynthesis. About 73.55% and 66.67% of the <i>MaUGT</i> genes were differentially expressed under ABA or abiotic stress in the shoots and roots, respectively. Furthermore, the functions of <i>MaUGT68</i> and <i>MaUGT186</i>, which were upregulated under stress and potentially involved in coumarin glycosylation, were characterized by heterologous expression in yeast and <i>Escherichia coli</i>. These results extend our knowledge of the <i>UGT</i> gene family along with <i>MaUGT</i> gene functions, and provide valuable findings for future studies on developmental regulation and comprehensive data on <i>UGT</i> genes in <i>M. albus</i>.