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Thermotolerance and post-fire growth in Rhizina undulata is associated with the expansion of heat stress-related protein families

Summary

Scientists sequenced the genome of a fungus called Rhizina undulata that uniquely depends on fire to activate its growth and infect conifer trees. By comparing this fungus to related species, they discovered it has extra copies of genes that produce special proteins for handling heat stress and dealing with the chemical changes that occur after fires. This finding helps explain how the fungus survives extreme heat and thrives in fire-damaged forests, which is important knowledge for forest management.

Background

Rhizina undulata is a pyrophilous fungus that infects conifer roots and relies on heat shock-mediated activation of ascospores, typically occurring after fire events in forests and plantations. The genetic mechanisms underlying this fungal thermotolerance have not been previously investigated. Understanding these mechanisms is important for forest management, particularly in regions where slash burning is used as a pest management practice.

Objective

To identify key genes and protein families responsible for thermotolerance in R. undulata by sequencing its genome and comparing the predicted proteome to other Pezizomycete species with and without known fire associations.

Results

Three protein families were significantly expanded in R. undulata: heat shock protein 20 (HSP20) which was uniquely overrepresented, glutathione-S transferases (GST), and aromatic compound dioxygenases (ACD). While HSP20 expansion was unique to R. undulata, GST and ACD expansions were also identified in other fire-associated Pezizomycete species, suggesting convergent evolution for fire adaptation.

Conclusion

The expansion of HSP20, GST, and ACD protein families suggests these proteins play critical roles in protecting R. undulata ascospores during fire-induced heat stress, detoxifying reactive oxygen species, and enabling metabolism of post-fire organic matter, thereby facilitating fungal colonization of conifer roots.
  • Published in:BMC Genomics,
  • Study Type:Comparative Genomics Study,
  • Source: 10.1186/s12864-025-11902-5; PMID: 41233753
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