Genome-wide identification of UGT gene family and their expression profiles analysis during fruit development in walnut (Juglans regia L.)

Abstract Walnut (Juglans regia L.) possess the ability to prevent coronary heart disease and promote cardiovascular health, which can be attributed to their rich content of polyphenols, particularly flavonoids. The biosynthesis of flavonoids is reliant on the catalytic activity of uridine diphosphate glycosyltransferase (UGT). However, the identification of UGTs in walnut has not been reported. In the current study, a total of 124 UGT genes containing the PSPG box were identified from the walnut genome. Based on phylogenetic analysis, the 124 UGT could be classified into 16 distinct groups, which exhibited an uneven distribution across the 16 chromosomes. Subcellular localization prediction analysis revealed that approximately 78.23% of walnut UGT proteins were predominantly localized in the cytoplasmic compartment. Furthermore, motif annotation confirmed that motifs 1, 2, and 3 represented conserved structural features within UGT proteins, while interestingly, around 56.5% of walnut UGT members lacked introns. In conjunction with transcriptome analysis and quantitative expression, approximately 39% of UGT genes in walnut exhibited high expression levels during early fruit development. Correlation analysis between UGT genes expression and phenolic content in walnut indicated that JrUGT6, JrUGT38, JrUGT39, JrUGT58, JrUGT69, JrUGT75, and JrUGT82 might be involved in phenolic biosynthesis in walnut. This comprehensive study provides a comprehensive overview of the UGT genes in walnut, serving as a valuable reference and theoretical foundation for further investigations into the biological functions of JrUGTs in flavonoid biosynthesis.