Integrated transcriptomic and metabolite analysis reveals the role of AktADT8 in the biosynthesis of phenylalanine and its derivatives in Akebia trifoliata

Arogenate dehydratase (ADT) is a key enzyme in plant phenylalanine (Phe) biosynthesis, providing precursors for protein and phenolic compounds. Akebia trifoliata is valued as a medicinal, fruit, and ornamental plant because of its abundance of Phe and derivatives. Among the 373 metabolites identified previously, 135 were phenolic compounds. Furthermore, analysis of 153 transcriptomic datasets from 53 samples across nine BioProjects revealed that AktADT3 and AktADT8 exhibited obvious stage-specific expression patterns. A total of 758 mutation sites were detected in AktADTs, with AktADT8 displaying a markedly higher proportion of synonymous variants. Co-expression analysis indicated that AktADT transcript abundance correlated significantly with the levels of 124 metabolites and 150 enzyme-encoding genes across five flavonoid biosynthesis pathways, with AktADT8 uniquely showing broad positive correlations across all pathways. Overexpression of AktADT6 and AktADT8 in Arabidopsis transformant lines presented significantly increased contents of Phe and flavonoids. Moreover, AktADT8 was uniquely characterized by two transcription start sites, and binding prediction suggested that MYB105 (where MYB is v-myb avian myeloblastosis viral oncogene homolog) could bind to the promoter region of AktADT8, whereas MYB21 could bind to the promoter regions of both AktADT8 and AktADTs8, thereby regulating their transcriptional activity. These findings highlight AktADT8 as a key candidate gene involved in Phe metabolism in A. trifoliata.