Phytotoxicity mechanism of rubratoxin B from the soil-derived fungus, Talaromyces purpureogenus XJ14C02.

Background

Chemical herbicides are essential for crop productivity, but increasing resistance demands new modes of action. Microbial metabolites offer a promising source of novel phytotoxins. Here, we elucidate the herbicidal mechanism of rubratoxin B (RB), a mycotoxin produced by Talaromyces purpureogenus XJ14C02 strain isolated from soil in Xinjiang, China.

Results

RB exhibited potent root growth inhibition against Echinochloa crus-galli, Conyza canadensis, and Arabidopsis thaliana (IC₅₀ = 14.70, 9.45, and 0.21 μg mL-1, respectively). Integrated multi-omics profiling identified 2373 differentially expressed genes, 518 differentially expressed proteins, and 151 differential metabolites, with the phenylpropanoid biosynthesis pathway consistently enriched across all three omics layers. RB activated upstream enzymes (PAL, 4CL, HCT) and led to accumulation of caffeoyl shikimic acid, while concurrently suppressing downstream flavonoid-related genes (CHS, CHI, F3H, DFR, ANS) and reducing coniferin levels. Arabidopsis mutants deficient in PAL or 4CL displayed markedly increased RB sensitivity, confirming the functional relevance of these nodes. Additionally, RB disrupted auxin distribution in root tips and caused severe ultrastructural damage.

Conclusion

RB disrupts the plant growth-defense balance through an 'upstream phenylpropanoid activation-downstream flavonoid inhibition' mechanism. Multi-omics integration coupled with mutant validation identifies PAL, 4CL, and F3H as critical functional mediators of RB phytotoxicity. These findings advance the mechanistic understanding of mycotoxin-driven herbicidal action and position RB as a promising lead scaffold for bioherbicide development. © 2026 Society of Chemical Industry.