Enzyme Repertoires and Genomic Insights into Lycium barbarum Pectin Polysaccharide Biosynthesis

Abstract Lycium barbarum, a member of the Solanaceae family, is an important eudicot with applications in both food and medicine. L. barbarum pectin polysaccharides (LBPPs) are key bioactive compounds of L. barbarum, notable for being among the few polysaccharides with both biocompatibility and biomedical activity. Although studies have analyzed the functional properties of LBPPs, the mechanisms underlying their biosynthesis and transport by key enzymes remain poorly understood. In this study, we assembled a 2.18-Gb reference genome of L. barbarum, reconstructed the first complete biosynthesis pathway of LBPPs, and elucidated the sugar transport system. We also characterized the important genes responsible for backbone extension, sidechain synthesis, and modification of LBPPs. Furthermore, we characterized the long non-coding RNAs (lncRNAs) associated with polysaccharide metabolism. We identified a specific rhamnogalacturonan I (RG-I) rhamnosyltransferase, RRT3020, which enhances RG-I biosynthesis within LBPPs. These newly identified enzymes and pivotal genes endow L. barbarum with unique pectin biosynthesis capabilities, distinguishing it from other Solanaceae species. Our findings thus provide a foundation for evolutionary studies and molecular breeding to expand the diverse applications of L. barbarum.