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Production of the light-activated elsinochrome phytotoxin in the soybean pathogen Coniothyrium glycines hints at virulence factor

Summary

Researchers discovered that a fungus infecting soybean plants produces red toxins that become dangerous when exposed to light. These toxins generate reactive oxygen species that damage plant cells, causing leaf spots and disease. The study found that disease is worse under light conditions but can still occur in darkness, suggesting multiple attack mechanisms. Understanding this toxin production may help develop better disease management strategies for soybean crops, particularly in Africa where the disease is common.

Background

Coniothyrium glycines causes red leaf blotch of soybean, a major disease in Africa and a USDA Select Agent due to its potential destructiveness. The fungus produces characteristic red lesions that expand during infection, causing defoliation and yield losses up to 50%. Despite its regulatory importance, no molecular basis of host infection has been previously reported.

Objective

This study investigated whether C. glycines produces light-activated perylenequinone phytotoxins similar to those in related fungal pathogens, and whether these toxins contribute to virulence in soybean infection.

Results

Light-grown cultures produced red-pink pigmentation, with six of eight genes in a perylenequinone biosynthetic gene cluster significantly upregulated under light. LC-MS/MS confirmed production of elsinochrome A and hypocrellin A, with significantly higher concentrations in light-grown tissue. Disease assays showed significantly more lesions developed under light conditions, though symptoms still occurred in darkness.

Conclusion

This is the first evidence that elsinochrome A contributes to virulence of C. glycines, with light-dependent toxin production enhancing disease severity. The findings suggest perylenequinone toxins have broader agricultural importance than previously recognized, with implications for management strategies.
  • Published in:PLoS One,
  • Study Type:Experimental Study,
  • Source: PMID: 40359450, DOI: 10.1371/journal.pone.0321896
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