Metabolic engineering of a tyrosine-specific phenylpropanoid pathway in plants

Van Beirs, C.; Bentelspacher, M.; Xie, C.; Van de Velde, C.; Desmet, S.; De Wulf, R.; Boerjan, W.; Barros-Rios, J.; Vanholme, B.

doi:10.64898/2025.12.16.694581

bioRxiv · 10.64898/2025.12.16.694581

Metabolic engineering of a tyrosine-specific phenylpropanoid pathway in plants

Van Beirs, C.·Bentelspacher, M.·Xie, C.·Van de Velde, C.·Desmet, S.·De Wulf, R.·Boerjan, W.·Barros-Rios, J.·Vanholme, B.

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Abstract

While all plants use L-phenylalanine for phenylpropanoid biosynthesis, grasses can also initiate the pathway from L-tyrosine. Curiously, no plant has evolved an exclusive tyrosine-derived route. We generate plants with phenylpropanoid biosynthesis initiated from phenylalanine, tyrosine, or both by expressing a Brachypodium phenylalanine/tyrosine ammonia-lyase (PTAL) in Arabidopsis WT and c4h mutants. Engineering a bifunctional phenylpropanoid pathway in WT plants did not negatively impact growth, while introducing a tyrosine-specific pathway in the c4h mutant could overcome the seedling-lethal phenotype. Interestingly, restored c4h mutants relying solely on the tyrosine route displayed developmental defects linked to the strong overaccumulation of the auxin transport inhibitor cis-cinnamic acid. Our findings suggest that the requirement of this widely overlooked plant metabolite could be the crucial factor for the evolutionary retention of the canonical phenylpropanoid biosynthesis route via L-phenylalanine in plants.

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Van Beirs, C., Bentelspacher, M., Xie, C., Van de Velde, C., Desmet, S., De Wulf, R., Boerjan, W., Barros-Rios, J., Vanholme, B.. 2025-12-16. Metabolic engineering of a tyrosine-specific phenylpropanoid pathway in plants. https://doi.org/10.64898/2025.12.16.694581

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