Phenylalanine-inducible OscWRKY7 regulates arogenate dehydratase-5 to alter phenylpropanoid metabolism in Ocimum sanctum

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The phenylpropanoid pathway varies across species and environments, producing diverse metabolites. The transcriptional regulation governing precursor feeding into this pathway remains largely unexplored. Here, we characterize OscWRKY7 TF, from Ocimum sanctum, as a positive regulator of arogenate dehydratase 5 (ADT5), a key shikimate pathway gene catalyzing the conversion of arogenate into phenylalanine. Phenylalanine treatment in O. sanctum induced key genes and metabolites of the phenylpropanoid pathway, with OscWRKY7 showing early induction. Recombinant OscWRKY7 interacts with the canonical W-box cis element and transactivates the reporter gene in yeast. Ectopic expression of OscWRKY7 in Arabidopsis thaliana induced transcriptomic changes in the shikimate and phenylpropanoid pathways, leading to upregulation of ADT5 transcripts, enhanced accumulation of phenylalanine and downstream metabolites. The biological function of OscWRKY7 was determined in Ocimum sanctum using gain- and loss-of-function approaches via hairy root-mediated overexpression and TRV-based VIGS. Overexpression of OscWRKY7 upregulated OscADT5 and enhanced phenylalanine accumulation, along with downstream phenylpropanoid metabolites, whereas silencing reduced them, providing evidence of OscWRKY7-mediated regulation of phenylpropanoid metabolism in O. sanctum. OscWRKY7 exhibits dual cis-element specificity, binding W-box and a non-canonical WT-box variant (TAACTTTT) in the OscADT5 promoter, suggesting a novel regulatory module. EMSA and Y1H demonstrated binding, while dual luciferase suggests transactivation of OscADT5 by OscWRKY7 through a non-canonical WT-box. OscWRKY7 further modulates phenylpropanoid pathway-associated genes to alter the accumulation of anthocyanin and salicylic acid, thereby enhancing plant defence response in Arabidopsis. Overall, our study suggests that OscWRKY7 promotes phenylpropanoid accumulation by facilitating the availability of phenylalanine, precursor of the phenylpropanoid pathway.