Genome-wide identification of the UGT gene family in foxtail millet and preliminary functional analysis of SiUGT26 during leaf senescence.

Plant uridine diphosphate glycosyltransferases (UGTs) catalyze glycosylation, a pivotal biochemical modification essential for diverse metabolic and physiological processes. Foxtail millet (Setaria italica), a drought-tolerant C4 cereal crop, serves as an emerging model for studying abiotic stress adaptation. Here, we identified 173 UGT genes (SiUGTs) in the foxtail millet genome, unevenly distributed across nine chromosomes and classified into 17 phylogenetically distinct subfamilies. Collinearity analysis revealed nine segmental duplicated duplication pairs under purifying selection, highlighting evolutionary conservation. Promoter analysis identified cis-acting elements associated with growth and development, biotic/abiotic stress responses, and hormonal regulation, suggesting functional versatility of SiUGTs. Transcriptome profiling under dark-induced leaf senescence (DIS) revealed 5 up-regulated and 27 down-regulated SiUGTs, implicating their roles in senescence regulation. Subsequently, RT-qPCR validated SiUGT26 as a senescence-responsive gene. Heterologous overexpression of SiUGT26 in Arabidopsis was associated with delayed leaf senescence and enlarged rosettes compared with wild-type plants. Co-expression analysis suggested that SiWRKY71 may be associated with the regulation of SiUGT26. Collectively, this study provides a genomic resource for the UGT gene family in foxtail millet and identifies SiUGT26 as a senescence-responsive candidate gene. These findings provide a basis for further investigation of UGT-mediated regulation of leaf senescence in foxtail millet.