Integrated metabolomics and transcriptomics reveal flavonoids glycosylation difference in two Citrus peels

Citrus reticulata 'Huajuhong' (HJH) and C. reticulata 'Sanhuhongju' (SHHJ) have distinct level of bioactive ingredients including flavonoid derivatives in peels meanwhile its underlying mechanism remain unclear. Integrated analysis of metabolome and transcriptome was comparatively investigated differences of HJH and SHHJ peels. The total flavonoid in HJH peels was significantly higher than that in SHHJ. Of 203 differentially accumulated metabolites (DAMs) and 3,517 differentially expressed genes (DEGs) were identified. KEGG enrichment analysis indicated that flavonoid pathway was overrepresented. Among the DAMs, the major components were flavonoids (104, 51.2%) followed by phenolic acids (30, 14.7%). Seven of top 10 flavonoid glycosides in HJH were highly accumulated and positively correlated with 10 glucosyltransferase genes. Collectively, higher content of flavonoid glycosides in HJH peels than in SHHJ peels might contribute to the distinct health-promoting effect, which provides a novel insight into improving the fruit quality of citrus as a health-promoting food resource.