Molecular dissection of novel anthocyanin transcripts HsCHS and HsF3H from the calyx tissue of Hibiscus sabdariffa L.

Abstract

Flavonoids are polyphenolic compounds commonly found in vegetables as well as fruits and contribute significantly in the human diet. The calyx of roselle (Hibiscus sabdariffa L.) is rich in polyphenolic compounds and anthocyanins. Chalcone synthase (CHS) and flavanone 3-hydroxylase (F3H) are two important genes involved in the biosynthesis of flavonoids including anthocyanins in plants. The two transcripts designated as HsCHS (KR709156) and HsF3H (KR709157) were isolated from the calyx tissue of roselle using the Rapid Amplification of cDNA Ends PCR and PCR walking approaches, which encoded the polypeptides of 389 and 368 amino acids, respectively. Several important domains were revealed in the HsCHS amino acid sequence, including CHS-like, fabH, BcsA, Chal-sti-synt-N and Chal-sti-synt-C, which indicates that the isolated gene is probably a CHS belonging to the polyketide synthase family. On the other hand, identification of 2OG-FeII_oxy, Isopenicillin N synthase-like, DIOXN and PLN02515 domains in HsF3H protein sequence supports the idea that the isolated gene is an F3H related to the large gene family of 2-oxoglutarate-dependent dioxygenases. This study predicted the putative functions of the two central genes governing the flavonoid pathway in H. sabdariffa, which leads to anthocyanin production.