Biosynthesis of delphinidin and resveratrol in three fruiting species

Abstract

Phenylpropanoids are plant secondary metabolites biosynthesized from the amino acid phenylalanine. They are a multifarious group of metabolites with diverse roles in processes such as pigmentation and defense. Major classes are the flavonoids and stilbenoids, represented by delphinidin and resveratrol respectively. Delphinidin, produced at the distal end of the phenylpropanoid biosynthesis pathway, is an anthocyanidin with pigment properties responsible for the blue hue of many flowers. In contrast, resveratrol is produced at the beginning of the phenylpropanoid biosynthesis pathway and is a phytoalexin synthesized by plants in response to microbial infection. While the general pathways producing these compounds are conserved within the plant kingdom, individual plant genera have evolved to include or exclude phenylpropanoid biosynthesis genes. The primary aim of this project is to investigate the ability of three species, apple (Malus x domestica), woodland strawberry (Fragaria vesca) and kiwifruit (Actinidia spp.), to synthesize delphinidin or resveratrol. Bioinformatic approaches were taken to identify a set of candidate genes from each species, which were narrowed down to core target genes for further molecular analysis. Gene expression of the target genes was measured over a variety of tissue types using qPCR. The metabolite profiles of transient assays involving target genes expressed in tobacco (Nicotiana tabacum) were obtained via HPLC and MS. A flavonoid3",5"-hydroxylase (AcF3'5'H) was identified in Actinidia spp. with expression patterns matching delphinidin presence and when transformed into tissue produces an increase in delphinidin production. Several type III polyketide synthase genes were identified in M. domestica and F. vesca, however none showed highest homology to stilbene synthase or produced resveratrol in transformed tissue.