Gene Expressions Involved in Flavonoid Biosynthetic Pathway Is Associated with Tannin Accumulation in Japanese Persimmon (Diospyros kaki Thunb.) Fruit

Japanese persimmons (Diospyros kaki Thunb.) are classified into the following four types depending on the effect of pollination on flesh colour and whether the fruit lose astringency on the tree: 1) pollination-constant non-astringent (PCNA), 2) pollination-variant non-astringent (PVNA), 3) pollination-variant astringent (PVA), and 4) pollination-constant astringent (PCA). Among these four types, PCNA-type is the most desirable persimmon for fresh consumption, since the fruit can be eaten always while firm without any postharvest treatments. The PCNA-type appeared uniquely in Japan probably due to the loss of the ability of tannin accumulation. PCNA-type fruit stops accumulating tannins at an early stage of fruit development. However, the molecular mechanism controlling tannin accumulation in persimmon is not so clear. Persimmon tannins are categorized into condensed tannins consisted of polymeric proanthocyanidins, which are synthesized via flavonoid biosynthetic pathway. So, we investigated varietal and seasonal changes in expressions of five genes involved in flavonoid biosynthesis (PAL, CHS, CHI, F3H, and DFR). The expressions of these genes were high until late stages of fruit growth in astringent-type, whereas those disappeared at an early stage of fruit growth in PCNA-type fruit. The relationship between transcripts of these genes and tannin accumulation in the fruit is discussed.