A plastoglobuli-localized enzyme links phenylalanine biosynthesis to translational homeostasis in maize

Aromatic amino acids are essential precursors for numerous plant metabolites, with phenylalanine (Phe) forming the basis of the phenylpropanoid pathway. Here, we reveal a critical mechanism for Phe biosynthesis in maize, demonstrating that all seven arogenate dehydratases (ADTs) are specifically localized to plastoglobuli (PGs) in chloroplasts, and ADT2.2 shows high catalytic activity towards arogenate and prephenate. This discovery establishes PGs as a site for Phe synthesis. Genetic analysis confirms that only ADT2.2 is indispensable for plant and seed development, with its loss causing a severe Phe deficiency in seeds. This metabolic blockage directly reduced the tRNA^Phe-GAA charging, thereby repressing protein translation. Crucially, we uncover that Phe starvation disproportionately affects the decoding efficiency of wobble-paired codons, increasing ribosome pausing. Our work provides biochemical and genetic evidence that PGs-localized ADT2.2 catalyzes Phe synthesis and reveals a link between amino acid availability and codon-specific translation dynamics.