Within the plant microbiota, mycorrhizal fungi are striking examples of microorganisms playing crucial roles in nutrient acquisition. They have coevolved with their hosts since the rise of land plants and the recent development of calibrated phylogenies, linked with the growing understanding of fungal genomes, provides remarkable insights into the evolutionary histories of mycorrhizal symbioses.
The comparison of 100+ genomes from mycorrhizal fungi, wood decayers and soil decomposers has revealed several independent lifestyle transitions from saprotrophism to mutualism in fungal lineages. In addition to reconstructing the evolution of mycorrhizal symbioses, our growing ability to use reference genomes for profiling differentially-expressed transcripts, for instance, is helping us to identify hundreds of symbiosis-related genes.
I will discuss recent genomic studies that have revealed the adaptations that seem to be fundamental to the convergent evolution of ectomycorrhizal fungi, including the loss of some metabolic functions, such as plant cell wall degrading enzymes, and the acquisition of small secreted effector-like proteins that facilitate the accommodation of symbiotic fungi within their host plants. Finally, I will consider how these insights can be integrated into a model of the development of ectomycorrhizal symbioses and pave the way to a better understanding of their role in carbon cycling in forest ecosystems.
Supported by the Laboratory of Excellence 'ARBRE' and the U.S. Department of Energy (ORNL Plant Microbe Interfaces project and the Joint Genome Institute). Thanks to the Mycorrhizal Genomics Consortium.
F. Martin, Tous les champignons portent-ils un chapeau? 90 clés pour comprendre les champignons, Ed. Quae
nutrition, forest fungi, wood decay, symbiosis