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Interruption of an MSH4 Homolog Blocks Meiosis in Metaphase I and Eliminates Spore Formation in Pleurotus ostreatus

Summary

This research identified the genetic basis for creating non-sporulating mushroom varieties, which has important practical applications. The scientists found that disrupting a specific gene (MSH4) prevents mushrooms from producing spores while maintaining their ability to grow and be harvested. This discovery has real-world impacts: • Improved worker safety by eliminating allergenic spores that cause respiratory problems • Better air quality in mushroom growing facilities due to reduced filter clogging • Reduced spread of viral diseases in mushroom crops • More stable mushroom production with maintained high yields • Potential for developing sporeless varieties in other edible mushroom species

Background

Pleurotus ostreatus (Oyster mushroom) is one of the most widely cultivated edible mushrooms but produces high numbers of spores that cause respiratory health problems, clog filters, and spread viral diseases. A non-sporulating commercial variety (SPOPPO) was introduced in 2006 through introgression breeding of a natural mutation.

Objective

To identify and characterize the gene(s) responsible for the sporeless phenotype in P. ostreatus to facilitate breeding of additional sporeless varieties and potentially develop sporeless varieties in other mushroom species.

Results

The sporeless phenotype was restored by re-introduction of the P. ostreatus meiotic recombination gene MSH4 homolog (poMSH4). Analysis showed that poMSH4 in the sporeless strain was interrupted by a DNA fragment containing a region encoding a CxC5/CxC6 cysteine cluster associated with Copia-type retrotransposons. Cytological studies revealed meiosis was blocked in metaphase I. Creating an MSH4 homolog knockout in S. commune resulted in extremely low spore formation.

Conclusion

MSH4 plays an essential role in both Class I and II crossovers in mushrooms, similar to animals but unlike plants. MSH4 homologs are likely to be effective breeding targets for developing sporeless strains both within Pleurotus species and other Agaricales. The findings provide a molecular basis for breeding sporeless mushroom varieties.
  • Published in:PLoS One,
  • Study Type:Genetic Analysis,
  • Source: 10.1371/journal.pone.0241749
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