How Gray Mold Fungi Adapt to Resist Plant Defenses and Become More Harmful

Jenn Hoskins
2nd August, 2024

How Gray Mold Fungi Adapt to Resist Plant Defenses and Become More Harmful

Image Source: Natural Science News, 2024

Key Findings

  • Researchers at Wageningen University in the Netherlands discovered four mechanisms that the fungus Botrytis cinerea uses to tolerate toxic saponins from plants
  • One key mechanism involves an enzymatic process that removes sugar from saponins, making them less harmful to the fungus
  • The study suggests that these tolerance mechanisms could be common among other plant and human pathogens, offering new insights for developing resistant crops and targeted fungicides
Plant secondary metabolites, such as saponins, play a crucial role in plant defense against pathogens and pests. Saponins are glycosylated triterpenoids, steroids, or steroidal alkaloids that exhibit broad-spectrum toxicity to various organisms. While secretion of glycosyl hydrolases has been the only known mechanism that enables fungal pathogens to colonize saponin-containing plants, recent research from Wageningen University in the Netherlands has uncovered additional mechanisms used by the fungus Botrytis cinerea to tolerate saponins from tomato and Digitalis purpurea[1]. The study utilized gene expression analyses, comparative genomics, enzyme assays, and extensive testing of fungal mutants to identify four distinct cellular mechanisms that B. cinerea employs to mitigate the toxic effects of saponins and enhance its virulence on saponin-producing plants. This research builds on previous findings that saponins act as defensive compounds in plants, deterring herbivores and pathogens[2][3][4]. One of the key findings of this study is the identification of a novel enzymatic deglycosylation mechanism unique to the interaction between B. cinerea and the saponins from its host plants. This mechanism involves the removal of sugar moieties from saponins, rendering them less toxic to the fungus. This discovery is significant because it adds a new dimension to our understanding of how pathogens can overcome plant defenses. In addition to this novel enzymatic mechanism, the study identified three other tolerance mechanisms that operate in the fungal membrane. These mechanisms are mediated by protein families that are widely distributed across the fungal kingdom, suggesting that similar strategies might be employed by other plant pathogenic fungi and even human pathogens. The researchers presented a spatial and temporal model to illustrate how these mechanisms work together to confer tolerance to saponins. The implications of this study are far-reaching. By uncovering these tolerance mechanisms, the research provides new insights into the evolutionary arms race between plants and pathogens. It also opens up potential avenues for developing new strategies to enhance crop resistance to fungal pathogens. For instance, understanding these mechanisms could help in breeding plants that produce saponins resistant to enzymatic deglycosylation or in developing fungicides that target these specific tolerance pathways. Previous studies have highlighted the importance of secondary metabolites like saponins in plant defense. For example, triterpenoid saponins in Barbarea vulgaris have been shown to deter insect pests, and their biosynthesis involves specific glycosyltransferases that glucosylate sapogenins, activating resistance[3]. Similarly, glucosinolates and saponins in B. vulgaris contribute to resistance against the diamondback moth, a specialist herbivore[4]. This new study extends our understanding by showing that pathogens like B. cinerea have evolved sophisticated mechanisms to counteract these plant defenses. In summary, the research from Wageningen University reveals that B. cinerea employs four distinct mechanisms to tolerate saponins, including a novel enzymatic deglycosylation process. These findings enhance our understanding of plant-pathogen interactions and could inform future efforts to improve crop resistance to fungal diseases. The study not only builds on previous knowledge about the role of secondary metabolites in plant defense but also provides a comprehensive model of how pathogens can overcome these defenses.

GeneticsBiochemPlant Science

References

Main Study

1) Botrytis cinerea combines four molecular strategies to tolerate membrane-permeating plant compounds and to increase virulence.

Published 31st July, 2024

https://doi.org/10.1038/s41467-024-50748-5

Related Studies

2) Secondary metabolites in plant innate immunity: conserved function of divergent chemicals.

https://doi.org/10.1111/nph.13325

3) UDP-glycosyltransferases from the UGT73C subfamily in Barbarea vulgaris catalyze sapogenin 3-O-glucosylation in saponin-mediated insect resistance.

https://doi.org/10.1104/pp.112.202747

4) Role of Saponins in Plant Defense Against Specialist Herbivores.

https://doi.org/10.3390/molecules24112067


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