Examining the genes and enzymes responsible for flavonoid level modification during fruit maturation in Chinese raspberry “Rubus chingii Hu”

Rubus chingii Hu, indigenous to China, is very rich in flavonoids. With the exception of anthocyanin, fruit flavonoids were much higher than most berries including other raspberry species, which partly contributed to its high phenolics and antioxidant capability. In contrast to other raspberries, anthocyanin and other flavonoids decreased as fruit matured. We investigated four typical phases of fruit maturation using transcriptomics, proteomics and metabolomics. The results indicate that the down-regulation of phenylpropanoid, flavonoid and anthocyanin biosynthesis are responsible for the metabolic decrease. The down-regulation of RcCHS (CL6140.Contig5) and RcCHI (Unigene14858 and Unigene22344) at gene and protein levels were associated with decreases of naringenin/naringenin chalcone respectively. Down-regulation of RcLAR (CL9527.Contig3) at gene and protein levels was consistent with decreases of afzelechin/epiafzelechin, catechin/epicatechin, and gallocatechin/epigallocatechin. However, multiple genes/proteins involved in the enzymatic pathways were divergent and differently regulated, e.g. Rc4CL genes/proteins were down-regulated while Rc4CL-like was maintained at constantly low levels.