Identification of genes in the phenylalanine metabolic pathway by ectopic expression of a MYB transcription factor in tomato fruit.

摘要

Altering expression of transcription factors can be an effective means to coordinately modulate entire metabolic pathways in plants. It can also provide useful information concerning the identities of genes that constitute metabolic networks. In this study, ectopic expression of a MYB transcription factor, Petunia hybrida ODORANT1, was used to alter Phe and phenylpropanoid metabolism in tomato fruits. Despite the importance of Phe and phenylpropanoids to plant and human health, the pathway for Phe synthesis has not been unambiguously determined. Microarray analysis of ripening fruits from transgenic and control plants permitted identification of a suite of coregulated genes involved in synthesis and further metabolism of Phe. The pattern of coregulated gene expression facilitated discovery of the tomato gene encoding prephenate aminotransferase, which converts prephenate to arogenate. Expression and biochemical data established an arogenate pathway for Phe synthesis in tomato fruits. Metabolic profiling and 13C flux analysis of ripe fruits further revealed large increases in the levels of a specific subset of phenylpropanoid compounds. However, while increased levels of these human nutrition-related phenylpropanoids may be desirable, there were no increases in levels of Phe-derived flavour volatiles.