Biosynthesis and Functional Roles of Plant Secondary Metabolites

Plant secondary metabolites encompass a vast array of specialised organic compounds derived from central metabolic pathways. Prominent classes include phenylpropanoids (such as flavonoids and lignins), terpenoids (monoterpenes to diterpenes) and alkaloids (including isoquinolines and tropanes). Biosynthesis typically initiates from amino acid precursors—most notably phenylalanine—followed by sequential enzyme-catalysed modifications that generate structural complexity. Transcriptional networks integrating R2R3-MYB, bHLH and WD40 factors orchestrate spatiotemporal expression of biosynthetic genes in response to developmental programmes and environmental stimuli. Functionally, secondary metabolites defend against herbivores and pathogens, attract pollinators and seed dispersers, and mediate symbiotic or antagonistic plant–microbe interactions. Many of these compounds exhibit potent antioxidant, antimicrobial or signalling activities, underscoring their ecological and agronomic importance. From an applied perspective, metabolic engineering of pathway enzymes has enabled enhanced production of valuable colourants, pharmaceuticals and nutraceuticals in both plant and microbial systems. A comprehensive grasp of biosynthetic routes, transport mechanisms and degradation processes is essential to optimise yield, stability and bioactivity for agricultural and industrial applications.

Research from Nature Portfolio

Recent studies have revealed novel enzymatic functions that complete long-standing gaps in flavonoid biosynthesis. Structural and biochemical analyses demonstrated that certain glutathione transferases, previously implicated only in anthocyanin transport, directly catalyse a dehydration step essential for cyanidin formation. Introduction of these enzymes into baker’s yeast boosted anthocyanin production by over thirty-fold, offering a robust platform for microbial synthesis of natural colourants. In parallel, work on cereal defence chemistry has identified a wheat-specific cytochrome P450 enzyme that converts flavanone substrates into O-methylated isoflavonoid phytoalexins. This alternative biosynthetic route, embedded in a genomic cluster acquired through ancient hybridisation, enhances pathogen resistance in modern wheat varieties without transgenic intervention.

Biosynthesis and Functional Roles of Plant Secondary Metabolites publication trend

The graph below shows the total number of articles in biosynthesis and functional roles of plant secondary metabolites across all publications each year (not limited to Nature Index journals).

Technical terms

Phenylpropanoid pathway: metabolic route converting phenylalanine into cinnamic acid derivatives that give rise to flavonoids, lignins and other phenolic compounds.

Anthocyanins: water-soluble flavonoid pigments responsible for red, purple and blue colours in plant tissues.

Glutathione transferases: enzymes that catalyse conjugation of glutathione to target molecules, here mediating a crucial step in anthocyanin biosynthesis.

Isoflavones: subclass of flavonoids predominantly found in legumes, serving as antimicrobial phytoalexins and signalling molecules in plant–microbe interactions.

Phytoalexins: inducible antimicrobial secondary metabolites synthesised by plants in response to pathogen attack.

References

1. The catalytic role of glutathione transferases in heterologous anthocyanin biosynthesis. Nature Catalysis (2023).
2. Discovery of isoflavone phytoalexins in wheat reveals an alternative route to isoflavonoid biosynthesis. Nature Communications (2023).
3. Trends in maintaining postharvest freshness and quality of Rubus berries. Comprehensive Reviews in Food Science and Food Safety (2023).
4. Anthocyanin Biosynthesis and Degradation Mechanisms in Solanaceous Vegetables: A Review. Frontiers in Chemistry (2018).
5. Plant Flavonoids—Biosynthesis, Transport and Involvement in Stress Responses. International Journal of Molecular Sciences (2013).