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Whole-Genome Sequence and Mass Spectrometry Study of the Snow Blight Fungus Phacidium infestans (Karsten) DSM 5139 Growing at Freezing Temperatures

Summary

This research investigated how a cold-loving fungus that causes snow blight disease in pine trees can survive and thrive in freezing temperatures. Scientists sequenced the fungus’s complete genetic code and studied the chemicals it produces at different temperatures. The study revealed that the fungus has special adaptations that allow it to grow under snow and kill tree needles in winter conditions. Impacts on everyday life: • Helps understand how plant diseases survive winter, which is important for forest management and tree farming • Could lead to new cold-resistant technologies based on the fungus’s survival strategies • May help develop better methods to protect young trees in nurseries from winter diseases • Provides insights for developing cold-adapted industrial enzymes • Could contribute to understanding how climate change might affect forest diseases

Background

Phacidium infestans is a significant pathogen affecting Pinus species across northern Europe and Asia. It causes ‘snow blight’ by growing under snowpack on infected seedling needles and killing them. The fungus can grow at sub-freezing temperatures and continues its growth at temperatures as low as -5°C. Previous studies have shown that snow cover affects fungal growth through water availability and insulation properties, with thicker snow cover and later snowmelt linked to increased needle loss and tree mortality.

Objective

This study aimed to sequence and analyze the complete genome of Phacidium infestans Karsten DSM 5139, investigate its enzymes, secondary metabolites, and adaptive mechanisms based on genome and proteome annotations. Additionally, the research sought to examine compounds secreted by the fungus at 22°C and -3°C through mass spectrometry analysis to understand its cold-adapted metabolism.

Results

The genome assembly resulted in 44 contigs with a total size of 36,805,277 bp and 46.4% GC content. Genome mining revealed numerous biosynthetic gene clusters coding for virulence factors and fungal toxins. The presence of pisatin demethylase indicated the fungus’s ability to detoxify terpenoid phytoalexins. Proteomic analysis revealed cold survival strategies including antifreeze proteins, trehalose synthesis enzymes, desaturases, and stress response proteins. The GH11 endoxylanase showed optimal activity at pH 5.0 and 45°C. Mass spectrometry analysis revealed differences in metabolite production between -3°C and 22°C conditions.

Conclusion

The study provides comprehensive insights into Phacidium infestans’ genome sequence, proteome, and secretome, revealing its unique adaptive mechanisms for surviving in freezing conditions. The findings demonstrate the fungus’s ability to adapt its metabolic processes and secretome to freezing temperatures through the production of osmoprotectant and cryoprotectant metabolites. This research advances understanding of cold adaptation in fungi and opens possibilities for biotechnological applications.
  • Published in:Molecular Genetics and Genomics,
  • Study Type:Genomic Analysis,
  • Source: 10.1007/s00438-023-02073-7
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