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Unveiling molecular mechanisms of strobilurin resistance in the cacao pathogen Moniliophthora perniciosa

Summary

Cacao farmers have struggled to control witches’ broom disease, a fungal infection caused by Moniliophthora perniciosa, because the fungus survives even high doses of strobilurin fungicides. This study reveals how the fungus adapts to the fungicide by switching its metabolism to use alternative energy sources, activating detoxification systems, and using an alternative respiratory pathway. Researchers also discovered that prolonged fungicide exposure can create even more resistant mutants with mutations in genes that control fungal growth and gene expression.

Background

Witches’ broom disease (WBD) of cacao, caused by Moniliophthora perniciosa, is a major agricultural problem in the Americas. Strobilurin fungicides, which inhibit mitochondrial respiration, have been ineffective against this pathogen. Previous studies identified the alternative oxidase (AOX) gene as contributing to strobilurin tolerance, but the complete molecular mechanisms remain poorly understood.

Objective

To investigate the molecular mechanisms underlying strobilurin tolerance in M. perniciosa and identify novel targets for improving fungicide efficacy. The study aimed to characterize the fungal transcriptional response to azoxystrobin exposure and understand how the pathogen survives high fungicide concentrations.

Results

M. perniciosa tolerated unusually high azoxystrobin concentrations without typical Cytb mutations. Transcriptomic analysis revealed metabolic reprogramming including upregulation of catabolic pathways (glyoxylate cycle, fatty acid degradation), respiratory chain remodeling, and strong induction of detoxification genes. Long-term fungicide exposure led to emergence of a resistant mutant (FDS01) with mutations in genes encoding putative growth and transcriptional regulators (MP02676 and MP01179).

Conclusion

M. perniciosa employs multifaceted mechanisms for strobilurin tolerance including metabolic adaptation, alternative respiration, and detoxification pathways rather than relying solely on Cytb mutations. The identification of mutated regulatory genes in the resistant mutant suggests that transcriptional reprogramming is a key mechanism of resistance. These findings provide targets for developing more durable fungicide strategies against WBD.
  • Published in:iScience,
  • Study Type:Experimental Study,
  • Source: 10.1016/j.isci.2025.113180, PMID: 40948559
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