Discovery of a novel phenylalanine degradation pathway in plants

Project Information

Phe-Degradation

Grant agreement ID: 101105068

DOI

10.3030/101105068

Project terminated on 4 March 2025

EC signature date 20 March 2023

Start date 1 April 2023

End date 31 March 2025

Funded under

• Marie Skłodowska-Curie Actions (MSCA)

Total cost

No data

EU contribution

€ 189 687,36

Coordinated by

MAX-PLANCK-GESELLSCHAFT ZUR FORDERUNG DER WISSENSCHAFTEN EV
Germany

Periodic Reporting for period 1 - Phe-Degradation (Discovery of a novel phenylalanine degradation pathway in plants)

Reporting period: 2023-04-01 to 2025-03-31

Summary of the context and overall objectives of the project

Plant aromatic amino acids, particularly phenylalanine (Phe), are precursors for a wide variety of specialized metabolites involved in defense, development, and communication. While the biosynthetic routes for these compounds are well characterized, much less is known about how Phe is degraded in plants. In contrast to animals and microbes, where Phe degradation has been intensively studied, plants appear to possess distinct, yet poorly defined catabolic pathways.

This project aimed to uncover a plant-specific degradation route of Phe via mandelate, a metabolite rarely studied in plant systems but with high industrial value. The identification and characterization of this pathway could open up new directions for metabolic engineering, enabling the sustainable production of valuable chemicals from renewable plant biomass.

The project addresses broader political and societal needs, such as the transition to environmentally sustainable production systems and the diversification of natural product supply chains. By improving our understanding of how plants manage aromatic amino acid metabolism in response to environmental signals, this research also provides insights into how plant metabolism may be optimized for changing climate conditions.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The project was structured into three work packages:

WP1 identified a candidate mandelate synthase through in vitro enzymatic assays and mutant analysis in Arabidopsis. Although the planned yeast complementation experiment was not performed, the biochemical and genetic evidence clearly supported the enzyme’s role in mandelate biosynthesis.

WP2 revealed that the mandelate pathway is strongly regulated by environmental light conditions. Under dark conditions, mandelate accumulation increases, whereas under high light, it decreases in favor of phenylpropanoid production. This metabolic switch is regulated by the activity of phenylalanine ammonia-lyase (PAL), a major gateway enzyme.

WP3, which aimed to examine volatile emissions from Phe metabolism, could not be completed due to the discontinuation of 14C-Phe and limited access to GC-MS facilities. Despite this, the core scientific objectives were achieved through the unexpected discovery of a light-regulated catabolic switch.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

This project identified a novel catabolic route for phenylalanine in plants, centered on the biosynthesis of mandelate—a compound previously overlooked in plant systems. An enzyme was functionally linked to mandelate production, and the conditions under which this pathway is favored were characterized for the first time.

A major discovery was the light-dependent metabolic switch between the mandelate and phenylpropanoid pathways, controlled by PAL activity. This adds a new layer of regulatory complexity to plant aromatic amino acid metabolism and provides a mechanistic entry point for tuning metabolic flow in response to environmental cues.

The findings offer potential for metabolic engineering to direct carbon flow toward desired end products such as mandelate or phenylpropanoids. Further research may enable the design of high-yield plant systems for sustainable bioproduction, and the enzymes identified could serve as bio-based tools in synthetic biology. To support uptake, continued collaboration with plant bioengineering and industrial biotechnology partners would be beneficial.