Genome-Wide Identification and Multi-Project Transcriptome Compendium Profiling of the UDP-Glycosyltransferase Gene Family in Litchi (Litchi chinensis Sonn.)

Litchi (Litchi chinensis Sonn.) is a high-value subtropical fruit crop prized for its unique flavor and nutritional profile. UDP-glycosyltransferases (UGTs) catalyze the glycosylation of diverse small molecules and play critical roles in fruit development, secondary metabolism, and stress responses, yet this gene family has not been systematically characterized in litchi. Here, we identified 102 LcUGT genes across the 15 litchi chromosomes and classified them into ten phylogenetic subfamilies. Duplication analysis indicated that whole-genome/segmental and tandem duplications were the major drivers. By integrating 212 public RNA-seq samples spanning diverse tissues, developmental stages, and stress conditions, we constructed a comprehensive expression atlas of the LcUGT family and identified candidate genes with divergent spatiotemporal patterns during fruit development. Co-expression network analysis further revealed tissue-specific modules, hub UGTs, and candidate upstream transcription factors associated with aril and seed development, and qRT-PCR assays in an additional cultivar showed expression trends consistent with the transcriptome data. This study provides the first genome-wide characterization of the litchi UGT gene family and offers candidate targets for molecular breeding of fruit quality and stress tolerance.