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Multiple Horizontal Mini-chromosome Transfers Drive Genome Evolution of Clonal Blast Fungus Lineages
Ana Cristina Barragan1, Sergio M Latorre2, Angus Malmgren1
1The Sainsbury Laboratory, University of East Anglia, Norwich Research Park, Norwich, UK.
Molecular Biology and Evolution
|August 6, 2024
Summary
Pandemic plant pathogens like the blast fungus adapt via horizontal chromosome transfer, not sexual reproduction. This process allows genetic exchange between lineages, with wild grasses acting as crucial reservoirs for pathogen evolution.
Area of Science:
- Plant Pathology
- Genetics
- Evolutionary Biology
Background:
- Crop disease pandemics are frequently driven by clonal plant pathogens reproducing asexually.
- The mechanisms enabling adaptation in these pathogens, despite limited genetic variation and lack of sexual recombination, are not well understood.
Purpose of the Study:
- To investigate the genetic mechanisms underlying adaptation in pandemic clonal lineages of the blast fungus Magnaporthe oryzae.
- To identify instances of genetic exchange and their role in pathogen evolution.
Main Methods:
- Comparative genomics to identify horizontally transferred DNA.
- Phylogenetic analysis to trace the evolutionary history of transferred elements.
- Population genetics to assess transfer events across different lineages.
Main Results:
- Identified a conserved 1.2Mb horizontally transferred mini-chromosome in Magnaporthe oryzae, present in both rice and Indian goosegrass infecting lineages.
- Documented at least nine distinct horizontal mini-chromosome transfer events into clonal rice blast isolates over the past 300 years.
- Demonstrated conservation of this mini-chromosome across distinct host-associated lineages.
Conclusions:
- Horizontal mini-chromosome transfer is a key mechanism for genetic exchange and adaptation in pandemic blast fungus lineages.
- Wild grass-infecting blast fungus populations serve as genetic reservoirs, fueling the evolution of crop-pathogenic lineages.
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