Expression of chalcone synthase and chalcone isomerase genes and accumulation of corresponding flavonoids during fruit maturation of Guoqing No. 4 satsuma mandarin (Citrus unshiu Marcow)

Chalcone synthase (CHS) and chalcone isomerase (CHI) are two key genes involved in flavonoid biosynthesis. They were both cloned from Guoqing No. 4 satsuma mandarin (Citrus unshiu Marcow), and their relative expression and accumulation of corresponding flavonoid components during fruit maturation were investigated by real-time PCR and HPLC techniques, respectively. During fruit maturation, expression of CHS and CHI genes declined gradually in peels, as well as the concentrations of total flavonoids, trans-chalcone, narirutin and hesperidin; in pulps, however, expression of both genes showed an approximately uptrend, and the concentrations of total flavonoids and those three components were detected in a lower level without significant changes among different developmental periods (P < 0.05). This research confirmed that expression of CHS and CHI genes was positively correlated with flavonoid accumulation and overexpression of them could be a potential approach to produce massive desired flavonoids in citrus fruits.