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Discovery of a New Starship Transposon Driving the Horizontal Transfer of the ToxA Virulence Gene in Alternaria ventricosa

Summary

Scientists discovered that a disease-causing gene called ToxA, previously found only in three wheat-infecting fungi, is also present in a fourth fungal species called Alternaria ventricosa. This gene travels between fungal species through special jumping DNA elements called Starships. The study reveals how fungi share dangerous genes through a process called horizontal gene transfer, which helps them become better at attacking crops. Understanding this process could help farmers and scientists develop better ways to prevent fungal diseases.

Background

The ToxA virulence gene has been previously identified in three fungal wheat pathogens (Parastagonospora nodorum, Pyrenophora tritici-repentis, and Bipolaris sorokiniana) and proposed to be horizontally transferred via a conserved ~14 kb ToxhAT transposon. This study expands the known distribution of ToxA to a new fungal species.

Objective

To identify and characterize ToxA in Alternaria ventricosa and investigate the role of Starship transposons in facilitating horizontal gene transfer of the ToxA virulence gene across fungal species.

Results

ToxA was identified in Alternaria ventricosa with 99.5% similarity to sequences in B. sorokiniana and P. tritici-repentis. The gene was embedded within a 14 kb ToxhAT transposon region nested in an 81.9 kb Starship element named Frontier. Three distinct HGT events were identified involving transfer of ToxA from P. nodorum to P. tritici-repentis, P. tritici-repentis to B. sorokiniana, and P. nodorum to A. ventricosa.

Conclusion

This study demonstrates that ToxhAT has been independently captured by three distinct Starship transposons (Frontier, Sanctuary, and Horizon), highlighting the pivotal role of transposon-mediated horizontal gene transfer in the adaptive evolution and pathogenicity of fungal pathogens. The discovery underscores the complex evolutionary dynamics of virulence gene dissemination among fungi.
  • Published in:Microorganisms,
  • Study Type:Comparative Genomics Study,
  • Source: PMID: 40005743, DOI: 10.3390/microorganisms13020376
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