Septembre 28 - 14h, Campus INRA Nouvelle-Aquitaine-Bordeaux (Room IBVM),
Understanding pathogen adaptation to the plant host.
Fungal plant pathogens pose a severe threat to global food security. These organisms often show exquisite host adaptation, but also undergo rapid evolution leading to shifts or expansions in the host range. The genetic mechanisms of pathogen-host adaptation remain poorly understood. In the soil-inhabiting vascular wilt fungus Fusarium oxysporum, individual isolates tend to exhibit high specificity towards a given plant host, while the species complex collectively attacks more than a hundred different crops. In addition, F. oxysporum is also an emerging human pathogen that provokes lethal systemic infections in immunocompromised individuals. Remarkably, a single field isolate of this funguscan kill tomato plants, immunodepressed mice and insects. By following a combination of reverse genetics and experimental evolution approaches, we found that F. oxysporum uses multiple strategies to adapt to different host environments. These include recruitment of conserved fungal signaling pathways or hijacking of host regulatory mechanisms for new virulence-related functions. Strikingly, fungal populations evolved after serial passaging through different environments displayed large-scale chromosomal reorganizations in transposon-rich accessory regions of the genome, suggesting that chromosome plasticity could act as a major evolutionary driver in F. oxysporum. Understanding the genetic mechanisms that govern virulence evolution and host adaptation may reveal new ways to control diseases caused by fungal pathogens and improve plant health.
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