Metabolome and transcriptome based investigation of anthocyanin accumulation in black wolfberry (Lycium ruthenicum) and validation of the function of LrUFGT.

Background: Black wolfberry (Lycium ruthenicum Murray) is renowned for its abundant anthocyanins, exhibiting antioxidant, anti-inflammatory, and anti-ageing activities. However, the accumulation patterns and molecular regulation of anthocyanins during fruit maturation are poorly understood. This study examined anthocyanin biosynthesis at three different stages: young fruit (LR-1), color transition (LR-2), and mature fruit (LR-3).

Results: The analysis revealed higher levels of anthocyanins in LR-3 (12.83 mg/g) than in LR-2 (9.76 mg/g) and LR-1 (8.41 mg/g), which established a correlation between anthocyanin accumulation and pericarp pigmentation. Antioxidant capacity assays demonstrated an increase in total antioxidant activity and hydroxyl radical scavenging ability during maturation. HPLC profiling identified three anthocyanidin aglycones: cyanidin, pelargonidin and delphinidin. LR-3 exhibited predominant cyanidin accumulation, while LR-1 lacked pelargonidin. Furthermore, the metabolomic analysis revealed that, the accumulation of three specific anthocyanins cyanidin-3,5-di-O-glucoside, cyanidin-3-sophoroside-5-glucoside, and pelargonidin, serves as the primary determinant of color variation in black wolfberry fruits. A transcriptomic investigation revealed the activation of structural genes (LrCHI, LrF3'H, LrF3'5'H) and glycosyltransferase gene LrUFGT. WGCNA and correlation analyses were then performed to identify networks coordinating anthocyanin biosynthesis. Functional characterization confirmed that chloroplast-localized LrUFGT catalysis cyanidin glycosylation to produce cyanidin-3-O-glucoside. Heterologous expression of LrUFGT in yeast led to enhanced tolerance to salinity and drought stress.

Conclusions: This multi-omics study provides a mechanistic understanding of anthocyanin regulation in black wolfberry, identifying targets for developing novel germplasms with elevated anthocyanin content. These findings establish a foundation for breeding strategies to enhance the nutritional quality and commercial value of black wolfberry.