Expression of the flavonoid 3′-hydroxylase and flavonoid 3′,5′-hydroxylase genes and flavonoid composition in grape ( Vitis vinifera)

Abstract

Flavonoid 3′-hydroxylase (F3′H) and flavonoid 3′,5′-hydroxylase (F3′5′H) are involved in the biosynthetic pathway of cyanidin- and delphinidin-based anthocyanins, respectively, as well as quercetin and myricetin (flavonols) and procyanidin and prodelphinidin (flavan-3-ols). Grape ( Vitis vinifera) accumulates these three classes of flavonoids and is presumed to have both F3′ h and F3′ 5′ h. Thus, we obtained the genomic sequences of F3′ h and F3′ 5′ h from grape and determined their mRNA levels as well as the flavonoid composition of several grape organs to investigate whether the transcription of these genes controls the flavonoid composition. The flower, stem, tendril, and seed, which accumulated a higher level of mRNA of F3′ h than F3′ 5′ h, showed reasonable compositions of flavonols and/or flavan-3-ols. The organs that accumulated a high level of F3′ 5′ h mRNA contained a high level of delphinidin-based anthocyanins (berry skin at the harvest stage) or prodelphinidin (small leaf), consistent with the mRNA levels. However, not all classes of flavonoid showed a similar composition according to the mRNA levels of F3′ h and F3′ 5′ h. The compositions of anthocyanins and flavonols in the small leaf were inconsistent with the mRNA levels. Consequently, other mechanisms in addition to gene transcription are also expected to control the composition of each flavonoid class.