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Genomic rearrangements generate hypervariable mini-chromosomes in host-specific isolates of the blast fungus

Thorsten Langner1, Adeline Harant1, Luis B Gomez-Luciano2

  • 1The Sainsbury Laboratory, University of East Anglia, Norwich Research Park, Norwich, United Kingdom.

Plos Genetics
|February 16, 2021
PubMed

Insights

Supernumerary mini-chromosomes in the blast fungus Magnaporthe oryzae are diverse and linked to virulence. These genomic variations arise from structural rearrangements and may drive fungal adaptation.

Area of Science:

  • Genomics
  • Mycology
  • Plant Pathology

Background:

  • Supernumerary mini-chromosomes are genomic variations linked to virulence in plant pathogens.
  • Mechanisms of mini-chromosome emergence and maintenance in fungi are poorly understood.
  • Mini-chromosomes in Magnaporthe oryzae were historically overlooked in genomic studies.

Purpose of the Study:

  • Investigate structural variation and mini-chromosome sequences in M. oryzae isolates.
  • Analyze the composition and genetic content of mini-chromosomes.
  • Understand the origins and evolutionary role of mini-chromosomes in M. oryzae.

Main Methods:

  • Comparative genomics of four M. oryzae isolates from different grass hosts.
  • Sequence analysis of mini-chromosomes from rice, foxtail millet, and goosegrass isolates.
  • Macrosynteny analysis to identify structural rearrangements and translocations.

Main Results:

  • Mini-chromosomes exhibit high diversity in sequence composition across isolates.
  • Mini-chromosomes are enriched in repetitive elements and have lower gene density than core-chromosomes.
  • Virulence genes, including Ace1 and AVR-Pik variants, were identified on the rice isolate's mini-chromosome.
  • Structural rearrangements, including translocations between core and mini-chromosomes, were observed.

Conclusions:

  • Mini-chromosomes originate from structural rearrangements and segmental duplication of core-chromosomes.
  • Mini-chromosomes contribute to the adaptive evolution of the blast fungus.
  • Further research into mini-chromosome dynamics is crucial for understanding fungal pathogenicity.

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