Abstract
Rubus chingii, is a red-fruited species of Rubus native to China, which is a popular and nutritious fruit in China. However, change in flavonoid composition and content during fruit maturation is poorly understood. This study examined flavonoids and the genes/proteins during four fruit ripening phases using LC-MS/MS. As a result, six major kinds of anthocyanins were first identified in R. chingii, which primarily consisted of flavanol-anthocyanins, are new to Rubus. Apart from anthocyanins, concentrations of fruit flavonoids were much higher than most berries including raspberries, and it is this that contributes to their high phenolic concentrations and antioxidant capabilities. In contrast to other known raspberries, R. chingii had a decline in flavonoids during fruit maturation, which was due to down-regulation of genes/proteins involved in phenylpropanoid and flavonoid biosynthesis. Surprisingly, anthocyanin continuously decreased during fruit coloration. This suggests that anthocyanins are not responsible for the fruit’s reddish coloration. The biosynthesis of these flavanol-anthocyanins consumed two flavonoid units both produced through the same upstream pathway. Their presence indicates a reduction in the potential biosynthesis of anthocyanin production. Also, the constantly low expression of RcANS gene down-regulated overall anthocyanin biosynthesis. The lack of RcF3’5’H gene/protein hindered the production of delphinidin glycosides. Flavonoids primarily comprising of quercetin/kaempferol-glycosides were predominately located at fruit epidermal-hair and placentae. The profile and biosynthesis of R. chingii flavonoids are unique to Rubus. It could be used to broaden the genetic base of raspberry cultivars and to improve their fruit quality.
Flavonoid Glycosides in Brassica Species Respond to UV-B Depending on Exposure Time and Adaptation Time
