Genome-Wide Analysis and Screening of Uridine Diphosphate-Glycosyltransferase Family Genes Involved in Lignin/Flavonoid Glycosylation and Stress Response in <i>Boehmeria nivea</i> (L.) Gaudich

Lignins and flavonoids, which are derived from the phenylpropanoid pathway and share common precursors, play an important role in <i>Boehmeria nivea</i> (ramie). Uridine diphosphate-glycosyltransferases (UGTs) are essential for the glycosylation of secondary metabolites and are involved in plant growth and stress responses. Hence, this study aimed to screen candidate <i>UGTs</i> related to lignin/flavonoid glycosylation and stress responses. A total of 84 <i>BnUGT</i>s were identified, and all <i>BnUGT</i>s contain a conserved PGPS domain. Phylogenetic analysis suggested that 10, 5, 1, and 1 putative <i>BnUGT</i>s might be associated with lignin glycosylation, flavonoid glycosylation, and adverse stress, respectively. Further analysis showed that <i>Bnt05T007753.1</i> expression was upregulated and showed a significant positive correlation with lignin content in the phloem and leaf, reaching up to 710 in the xylem after 75 days of germination. <i>Bnt14T019888.1</i> expression (in the leaf and xylem) and <i>Bnt06T010117.1</i> expression (in the xylem) were upregulated and showed a significant positive correlation with lignin and flavonoid content. In the phloem, <i>Bnt14T019888.1</i> expression was downregulated and showed a significant negative correlation with lignin content. <i>Bnt04T006105.1</i> expression was upregulated in the stem and leaf under Cd treatment. Overall, we successfully identified four candidate <i>BnUGTs</i> (<i>Bnt05T007753.1</i>, <i>Bnt14T019888.1, Bnt06T010117.1</i>, and <i>Bnt04T006105.1</i>); these findings provide insight into the glycosylation mechanisms of lignins and flavonoids and stress responses in ramie.