Effect of Phenyllactic Acid on the Biosynthesis of Proanthocyanidin and Anthocyanin in Winter Jujube Fruits

This study was performed to evaluate the effect of postharvest immersion in 1.0 g/L phenyllactic acid solution on the biosynthesis of anthocyanin and proanthocyanidin in winter jujube fruits. The results demonstrated that treatment with phenyllactic acid up-regulated the expression levels of transcription factors, including ZjMYB1R1, ZjMYB13/44/101, and ZjbHLH13/35/47/62. Conversely, it inhibited the expression levels of both ZjbHLH30 and ZjMYB30. Concomitantly, the gene expression levels of phenylalanine ammonialyase, 4-coumarate coenzyme A ligase, cinnamic acid-4-hydroxylase, chalcone isomerase, chalcone synthase, flavanone 3-hydroxylase, flavanone 3'-hydroxylase, anthocyanidin synthase, dihydroflavonol 4-reductase, UDP-glucose:flavonoid-3-O-glucosyltransferase 3, anthocyanidin reductase, and leucoanthocyanidin reductase were up-regulated by phenyllactic acid, resulting in the accumulation of anthocyanin and proanthocyanidin. Also, phenyllactic acid treatment reduced the accumulation of hydrogen peroxide. These findings suggest that phenyllactic acid promotes the biosynthesis of anthocyanin and proanthocyanidin in winter jujube fruits by enhancing the expression of key genes involved in their biosynthesis through the activation of bHLH and MYB transcription factors, thereby enhancing antioxidant capacity.