Identification and comparative expression analysis of chalcone synthase, flavanone 3-hydroxylase and dihydroflavonol 4-reductase genes in wild pomegranate ( Punica granatum L.) organs

Flavonoids are the predominant polyphenolic compounds which are ubiquitously present in plants, responsible for the colour development in different plant parts, thereby playing an important role in plant physiology. In order to understand chemo-diversity and biological functions of flavonoids, it is important to understand flavonoid biosynthetic pathway that involves various structural genes. Three structural genes of flavonoid biosynthetic pathway, chalcone synthase (PgCHS; GenBank accession no: KY498075), flavanone 3-hydroxylase (PgF3H; GenBank accession no: MG012857) and dihydroflavonol 4-reductase (PgDFR; GenBank accession no: MG366127) were isolated and characterized from the wild Punica granatum. Molecular modelling indicated that the secondary structures of PgCHS, PgF3H and PgDFR are mainly α-helix and random coils. HPLC analysis of flavonoids showed its accumulation in different tissues and fruits, thus corroborating well with the expression profile of PgCHS, PgF3H and PgDFR genes. PgF3H and PgDFR genes exhibited high transcripts levels in red fruits while expression of Pg CHS gene was highest in flowers. Further, it is speculated that expression of all these structural genes is independent of each other. This is the first study that provides a comparative expression pattern of flavonoid genes playing a significant role in fruit ripening in wild pomegranate.