Citric acid impairs type B trichothecene biosynthesis of Fusarium graminearum but enhances its growth and pigment biosynthesis: transcriptomic and proteomic analyses

Summary

Researchers discovered that citric acid, a natural acid found in plant roots and commonly used in agriculture, can reduce the production of dangerous mycotoxins called trichothecenes that contaminate wheat and corn crops. While citric acid surprisingly boosts the fungus’s growth and changes its color, it simultaneously shuts down the genes responsible for producing these toxic compounds. This discovery could help farmers use citric acid more strategically to prevent Fusarium head blight, a devastating crop disease, though care must be taken since it also promotes fungal growth.

Background

Fusarium graminearum is a soil-borne pathogenic fungus that causes devastating plant diseases such as Fusarium head blight, leading to significant crop losses and accumulation of mycotoxins that threaten food safety and human health. Citric acid is a plant root exudate and heavy metal chelator that interacts with F. graminearum in complex soil environments, but its comprehensive effects on fungal metabolism remain poorly understood.

Objective

This study investigated the effects of citric acid at concentrations of 2.5, 5, 10, and 20 mM on F. graminearum growth, pigment biosynthesis, and type B trichothecene production using integrative transcriptomic and proteomic analyses.

Results

Citric acid treatment promoted fungal growth through upregulation of carbon metabolism enzymes (PEPCK, Glpk, LAI12) and altered mycelial pigmentation through upregulation of polyketide biosynthetic enzymes (AurF, AurJ, AurT). Notably, citric acid significantly downregulated many Tri genes and trichothecene biosynthetic proteins despite promoting fungal growth, with the 10 and 20 mM groups showing the most dramatic effects compared to lower concentrations.

Conclusion

Citric acid acts as a type B trichothecene biosynthesis inhibitor while simultaneously promoting fungal growth and pigment biosynthesis, suggesting it functions as a double-edged sword for F. graminearum survival. These findings provide theoretical basis for understanding plant-soil-fungal interactions and informing reasonable agricultural applications of citric acid for preventing Fusarium head blight.
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