Benzoxazinoid Biosynthesis in Cereal Plants

Benzoxazinoids are a group of indole‐derived secondary metabolites predominantly found in grasses such as maize, wheat and rye. Biosynthesis commences in plastids where indole‐3‐glycerol phosphate is converted to indole by the enzyme BX1, a specialised tryptophan synthase α‐type lyase. Subsequent oxidation steps are carried out by a series of cytochrome P450 monooxygenases (BX2–BX5), transforming indole through hydroxylation reactions into 2,4‐dihydroxy‐1,4‐benzoxazin‐3‐one (DIBOA). DIBOA is then glycosylated to DIBOA‐glucoside and further modified by the dioxygenase BX6 and the methyltransferase BX7 to yield 2,4‐dihydroxy‐7‐methoxy‐1,4‐benzoxazin‐3‐one‐glucoside (DIMBOA‐glc). These glucosylated forms are stored in vacuoles and activated upon tissue damage, releasing bioactive aglycones with insecticidal, antimicrobial and allelopathic properties. The genes encoding these enzymes are often organised in clusters on cereal chromosomes, ensuring coordinated expression. Biosynthetic flux and accumulation are regulated by developmental cues and environmental stimuli, including herbivory, drought and phytohormones. Natural variation in gene copy number, sequence and promoter architecture underlies inter‐ and intra‐species diversity in benzoxazinoid profiles. Beyond defence, benzoxazinoids influence plant–microbe and plant–plant interactions, and their chemical stability during grain processing raises potential implications for human nutrition and health. Advances in genome editing and pathway engineering continue to explore the enhancement of benzoxazinoid content for sustainable crop protection and allelopathic weed management.

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Benzoxazinoid Biosynthesis in Cereal Plants publication trend

The graph below shows the total number of articles in benzoxazinoid biosynthesis in cereal plants across all publications each year (not limited to Nature Index journals).

Technical terms

Benzoxazinoid: Indole‐derived secondary metabolite with defensive and allelopathic functions in grasses.

Indole-3-glycerol phosphate: Biosynthetic precursor converted by BX1 to indole in the benzoxazinoid pathway.

Cytochrome P450: Family of monooxygenase enzymes (e.g. BX2–BX5) that catalyse hydroxylation steps in benzoxazinoid biosynthesis.

Glucoside: Sugar‐conjugated form of benzoxazinoid aglycones, stored in plant vacuoles as inactive precursors.

UDP-glucosyltransferase: Enzyme that transfers glucose from UDP‐glucose to benzoxazinoid aglycones, forming stable glucosides.

References

1. Characterisation of the tryptophan synthase alpha subunit in maize. BMC Plant Biology (2008).
2. Elucidation of the Final Reactions of DIMBOA-Glucoside Biosynthesis in Maize: Characterization of Bx6 and Bx7. Plant Physiology (2008).
3. Phylogenomics of the benzoxazinoid biosynthetic pathway of Poaceae: gene duplications and origin of the Bx cluster. BMC Ecology and Evolution (2012).
4. Genetic Variation, DIMBOA Accumulation, and Candidate Gene Identification in Maize Multiple Insect-Resistance. International Journal of Molecular Sciences (2023).
5. Reinventing metabolic pathways: Independent evolution of benzoxazinoids in flowering plants. Proceedings of the National Academy of Sciences of the United States of America (2023).
6. Genome-wide identification, phylogenomics, and expression analysis of benzoxazinoids gene family in rice (Oryza sativa). Plant Stress (2023).
7. Isolation and Structure Determination of Drought-Induced Multihexose Benzoxazinoids from Maize (Zea mays). Journal of Agricultural and Food Chemistry (2024).