Note:  Bofei Yang and Yan Song contributed equally.
Abstract: BACKGROUND:Blueberry fruits contain large amounts of phenolic compounds derived from the phenylpropanoid pathway. Their biosynthesis is complex, involving many enzymes. OBJECTIVE:We sought to investigate the content of phenylpropanoid-derived compounds and identify key genes involved in the phenylpropanoid metabolite pathway during half-highbush blueberry fruit development. METHODS:Phenylpropanoid metabolite contents were determined by high-performance liquid chromatography (HPLC) and spectrophotometry. Gene expression was examined through reverse-transcription PCR. RESULTS:Phloretin, chlorogenic acid, total flavonol, quercetin, catechin, and proanthocyanidin contents were highest in small-sized green fruits; myricetin and epicatechin contents were highest in pink fruits; and lignin and anthocyanin were highest in blue fruits. Genes from the 4-coumarate CoA ligase (4CL) family regulate the biosynthesis of phenylpropanoid metabolites. Phenylalanine ammonia-lyase (PAL) and cinnamoyl-CoA reductase (CCR) are key genes in the lignin biosynthetic pathway. Flavonol synthase (FLS) is a key gene affecting total flavonols and the quercetin biosynthetic pathway. PAL and chalcone isomerase (CHI) are key genes in the epicatechin and anthocyanin biosynthetic pathways, respectively. CONCLUSION:Phenylpropanoid metabolites are regulated by multiple genes from the same or different families. Enzymes in different metabolic pathways compete for precursors to form a complex regulatory network for phenylalanine metabolism.