Fruit development and ripening orchestrating the biosynthesis and regulation of Lycium barbarum polysaccharides in goji berry

Lycium barbarum polysaccharides (LBPs) are the primary bioactive components in fruits of L. barbarum, commonly known as goji berry. Despite significant progress in understanding the chemical structures and health benefits of LBPs, the biosynthesis and regulation of LBPs in goji berry remains largely unknown. In this study, physiological indicators, including LBPs, were monitored in goji berry during fruit development and ripening (FDR), suggesting that pectin might be the major component of LBPs with increased content reaching 235.8 mg/g DW. Proteomic and transcriptomic analysis show that 6410 differentially expressed genes (DEGs) and 2052 differentially expressed proteins (DEPs) were identified with overrepresentation of flavonoids and polysaccharides-related gene ontology (GO) terms and KEGG pathways. Weighted gene co-expression network analysis (WGCNA) showed that LBPs coexpress with genes involved in pectin biosynthesis (LbGALS3, LbGATL5, LbQUA1, LbGAUT1/4/7, LbRGGAT1, LbRRT1/7, and LbRHM2), modification (LbSBT1.7), and regulation (LbAP2, LbGL2 LbTLP2, LbERF4, and LbTTG2), as well as with novel transcription factors (LbSPL9 and LbRIN homologs) and glycosyltransferases. Transgenic hairy roots overexpressing LbRIN validated that LbRIN modulate the expression of WGCNA-predicted regulators, including LbERF4, LbTTG2, and LbSPL9. These findings suggest that the biosynthesis and regulation of LBPs is conserved partially to those in Arabidopsis pectin. Taken together, this study provides valuable insights into the biosynthesis and regulation of LBPs, which can facilitate future studies on synthetic biology applications and genetic improvement of LBPs.