"Mating, Pheromone-signalling pathway and genetic exchange in arbuscular mycorrhizal fungi"

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Arbuscular mycorrhizal fungi (AMF) are root-inhabiting symbionts organisms, and among the most common soil fungi. AMF form symbioses with the roots of approximately 80% of all vascular plant species. These fungi offer a variety of services, in particular, improved capacity for P uptake and drought tolerance. From a genetic point of view, AMF are extremely complex when compared to most other eukaryotes. AMF are coenocytic organisms that contain thousands of nuclei throughout their life cycle. There is much evidence that these nuclei are genetically divergent, and fungal isolates show extensive intracellular genetic polymorphism. Therefore, many fundamental questions bearing on AMF biology remain difficult to investigate. Arbuscular mycorrhizal fungi are presumed to be asexual organisms that are reproducing via large multinucleated spores. Sexual reproduction has never been observed on AMF. The goal of this research program is to investigate if AMF do have sex. This work exploits high-throughput genomic approaches to investigate four specific objectives: (1) to characterize pheromone-signalling pathway in Glomus species; (2) to study the genomic structure of the Glomus species sex locus and to compare the gene synteny of Glomus sex locus to Mucorales and Microsporidia species; (3) to induce sexual reproduction between several Glomus irregulare isolates using trisporic acids, a pheromone commonly secreted by Mucoromycotina, and to track gene expression of some key genes using quantitative PCR; (4) to study gene exchange between genetically different AMF isolates by using crossing experiments and subsequent genotyping with mitochondrial DNA markers.