Molecular Identification and Characterization of UDP-glycosyltransferase (UGT) Multigene Family in Pomegranate

Abstract

Pomegranate (Punica granatum L.) is regarded as one of the functional fruits because of its large amounts of secondary metabolites. The glycosylation processes mediated by UDP-glycosyltransferases (UGTs) play a decisive role in regulating secondary metabolite availability. In this study, a genome-wide search identified 145 UGT genes in pomegranate, and further phylogenetic analysis defined 17 distinct groups: A to P and R. PgUGTs were dispersed unevenly across all eight chromosomes. Duplication events analysis revealed that both segmental and tandem duplications were the main mechanisms leading to gene family expansions. The comparison of exon–intron patterns identified 53 intron-less genes. A total of 24 types of cis-acting elements related to hormone, stress, and developmental responses were predicted in the promoter regions. Expression analysis of PgUGT genes using RNA-seq data and quantitative real-time PCR (qRT-PCR) verification suggested that PgUGT genes were expressed at specific stages of fruit development, and different PgUGT members likely played different roles in specific fruit developmental stages. In an attempt to identify the UGTs involved in the glycosylation of flavonoids, 44 PgUGTs were putatively determined, and 5 well-defined orthologous groups (OGs) were characterized by the regioselectivity of these enzymes. These results provide significant insight into the UGT multi-gene family in pomegranate, and will be helpful to further elucidate their roles involved in secondary and specialized metabolism in pomegranate.