Evolution and Diversity of Sexually-Related Genes in the Arbuscular Mycorrhizal Fungus Rhizophagus irregularis

• Main Author: Charron, Philippe
• Other Authors: Corradi, Nicolas
• Language: en
• Published: Université d'Ottawa / University of Ottawa 2015
• Subjects: Fungi; Bioinfomatics
• Online Access: http://hdl.handle.net/10393/33375; http://dx.doi.org/10.20381/ruor-3971

Arbuscular mycorrhizal fungi (AMF) are ancient organisms that form symbioses with more than 80% of land plants. Fossil evidence of this partnership dates back 460Ma, when land was first colonized by plants. The mutualistic relationship between host roots and the fungus consists of an exchange of essential nutrients for the proliferation of both organisms, highlighting the importance of the mycorrhizal symbiosis. Despite their extreme longevity, a lack of evidence supporting sexual reproduction has labelled AMF as asexual organisms. However, recent evidence seems to point towards the potential of a cryptic sexuality. Specifically, AMF genomes encode for homologues of proteins that have a role in sexual processes in other fungi, including several typically involved in partner recognition, such as mating-type high mobility group (MATA-HMG) proteins found in mating-type loci. In my thesis, I expanded our analyses to five isolates of the AMF model organism Rhizophagus irregularis, through the acquisition of novel genome data. Some key findings consist of an expansion of MATA-HMG proteins, their unique organizations throughout the genome and the presence of a conserved fungal pheromone pathway. In retrospect, this research uncovers an unprecedented number of AMF genes that are homologues to sex-related genes of other fungi and reveals for the first time their atypical genomic architecture, providing valuable information towards the identification of a cryptic sexuality in these ecologically and economically important organisms.