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Genome structure impacts molecular evolution at the AvrLm1 avirulence locus of the plant pathogen Leptosphaeria

Lilian Gout1, Marie Line Kuhn, Lucie Vincenot

  • 1INRA, UMR1290 BIOGER-CPP, F-78026 Versailles, France. gout@versailles.inra.fr

Environmental Microbiology
|November 10, 2007
PubMed

Insights

Leptosphaeria maculans rapidly evolves virulence against oilseed rape by deleting the AvrLm1 gene. This large deletion, often conserved across pathogen populations, suggests retrotransposons drive adaptation.

Area of Science:

  • Plant pathology
  • Fungal genetics
  • Genomics

Background:

  • Leptosphaeria maculans causes oilseed rape stem canker through gene-for-gene interactions.
  • Pathogen populations rapidly adapt to host resistance, exemplified by evolution of virulence at the AvrLm1 locus.
  • The AvrLm1 avirulence gene is located in a large non-coding region.

Purpose of the Study:

  • Investigate the molecular basis of virulence evolution at the AvrLm1 locus.
  • Analyze the genomic region of AvrLm1 in virulent and avirulent isolates.
  • Determine the frequency and conservation of virulence-associated genomic changes.

Main Methods:

  • Whole-genome sequencing of selected L. maculans isolates.
  • Comparative genomic analysis of the AvrLm1 region.
  • Analysis of a large collection of isolates from diverse geographic locations.

Main Results:

  • Virulent isolates exhibited a large (260 kb) deletion encompassing the AvrLm1 gene.
  • Deletion breakpoints were conserved across isolates, suggesting a common origin.
  • Over 90% of virulent isolates analyzed possessed a similar deletion, indicating rapid diffusion.
  • Retrotransposons were implicated as drivers of these genomic rearrangements.

Conclusions:

  • Large deletions are a primary mechanism for rapid evolution of virulence in L. maculans.
  • Conserved deletion breakpoints suggest a unique evolutionary event.
  • Retrotransposons play a significant role in pathogen adaptation and genome evolution.

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