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Cytoplasmic Mixing, Not Nuclear Coexistence, Can Explain Somatic Incompatibility in Basidiomycetes

Summary

This research explores how mushroom-forming fungi can recognize and reject ‘foreign’ fungal tissue while allowing necessary cellular fusion during reproduction. The study proposes a new model explaining how fungi maintain their individual identity while still being able to mate and reproduce successfully. This has important implications for understanding fungal biology and potentially improving mushroom cultivation. Impacts on everyday life: • Helps improve commercial mushroom breeding and cultivation techniques • Advances our understanding of how organisms maintain their genetic identity • Could lead to better methods for controlling fungal growth in agriculture • May contribute to developing new strategies for preventing fungal diseases • Could assist in improving yields in mushroom farming

Background

Nonself recognition leading to somatic incompatibility (SI) is commonly used by mycologists to distinguish fungal individuals. The process remains poorly understood in basidiomycetes as current models are based on ascomycete fungi. While ascomycete fungi are mainly found in a monokaryotic stage with a single type of haploid nuclei, basidiomycete fungi have an extended heterokaryotic stage and SI is generally observed between heterokaryons instead of homokaryons.

Objective

To develop a model explaining how nonself recognition functions in basidiomycete fungi, particularly addressing how two different nuclear genomes can coexist in heterokaryons while maintaining the ability to recognize nonself individuals. The study aims to translate knowledge from ascomycete systems to understand basidiomycete biology and explore the consequences of such mechanisms.

Results

The study found that a post-translational modification system based on reader-writer proteins provides the most promising model for basidiomycete nonself recognition. This system allows stable heterokaryons while maintaining the ability to recognize nonself individuals. The model explains how nuclear migration during mating can enable successful fusion despite triggering localized cell death. The researchers determined that fewer polymorphic loci may be needed in basidiomycetes compared to ascomycetes due to the presence of two genomes in heterokaryons providing increased specificity.

Conclusion

The study proposes that nuclear migration is crucial for understanding how nonself recognition works in basidiomycetes, possibly through a dose-dependent post-translational modification system using reader-writer proteins. This model can explain the coexistence of two nuclear haplotypes in a single cytoplasm while maintaining the ability to recognize and reject nonself individuals, effectively limiting the spread of parasitic cytoplasmic elements at all life stages.
  • Published in:Microorganisms,
  • Study Type:Review,
  • Source: 10.3390/microorganisms9061248
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