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A l'occasion des Journées Jean Chevaugeon (JJC2024) à Aussois, le prix du meilleur poster a été attribué à Axelle Deroubaix (doctorante dans l'équipe ECCP)

Titre du poster : Systematic inactivation of the fungal biosynthetic gene clusters expressed during the Colletotrichum higginsianum- Arabidopsis thaliana interaction

Auteurs du poster : Axelle Deroubaix, Justine Vergne, Célia Perdrizet, Clara Centa, Richard J. O’Connel, Muriel Viaud, Jean-Félix Dallery
Université Paris-Saclay, INRAE, UR BIOGER, 91120 Palaiseau, France

Résumé : In the context of reducing pesticide use, a better understanding of the molecular mechanisms of fungal pathogenesis is essential for developing new methods of plant disease control. Plant pathogenic fungi secrete a range of molecules during host infection, including proteins and specialized metabolites (SM). SM are small molecules produced by both plants and microorganisms, which have a wide variety of bioactivities. Mainly known for their phytotoxic activities, SM can also have effector-like functions by manipulating immune responses and other physiological processes of the host plant. In fungal genomes, biosynthetic genes are generally found at the same genetic locus in so-called biosynthetic gene clusters (BGC) and contain at least a key enzyme that initiates the formation of a backbone molecule, that is subsequently modified by one or more accessory enzymes. Within the ascomycetes, Colletotrichum species are known to have large repertoires of BGCs. C. higginsianum is the causal agent of anthracnose disease on Brassicaceae. This hemibiotrophic phytopathogen has a biotrophic phase confined to a single epidermal cell, is able to colonize the model plant Arabidopsis thaliana, and high-quality genomes are available for both partners. These features make this pathosystem a useful model where both partners are genetically tractable. Transcriptomics data revealed the specific expression of 19 BGCs during plant infection and 14 of these are specific to the biotrophic phase. The aim of the project is to decipher the role of SM produced during the biotrophic phase of C. higginsianum. As the fungus develops in a living cell, it is assumed that the SMs produced at that stage are not phytotoxins but could instead have a role in niche competition with other microbes, as stress resistance factors, or as effectors for host manipulation. The inactivation of each of these 14 BGCs was initiated as part of my thesis and the pathogenicity of the resulting mutants is currently being tested on A. thaliana. As these molecules are not produced in axenic conditions, a heterologous expression system in Saccharomyces cerevisiae will be used to produce promising compounds. This will allow to isolate the SMs in quantities large enough to decipher their structure and biological activities.