Convergent losses of decay mechanisms and rapid turnover of symbiosis genes in mycorrhizal mutualists

Mycorrhizal Genomics Initiative Consortium, Anders Tunlid, Igor V. Grigoriev, David S. Hibbett, Francis Martin The Mycorrhizal Genomics Initiative includes: Marc Buée, Yi Din, Monique Gardes, Gwen Grelet, Hervé Gryta, Patricia Jargeat, Yaron Sitrit and Sabine Zimmermann (SZ : Aff: UMR 5004 Biochimie et physiologie moléculaire des plantes/CNRS/INRA/Montpellier Supagro/UM2, 2 place Viala , Bât 7, IBIP, 34060 Montpellier)To elucidate the genetic bases of mycorrhizal lifestyle evolution, we sequenced new fungal genomes, including 13 ectomycorrhizal (ECM), orchid (ORM) and ericoid (ERM) species, and five saprotrophs, which we analyzed along with other fungal genomes. Ectomycorrhizal fungi have a reduced complement of genes encoding plant cell wall-degrading enzymes (PCWDEs), as compared to their ancestral wood decayers. Nevertheless, they have retained a unique array of PCWDEs, thus suggesting that they possess diverse abilities to decompose lignocellulose. Similar functional categories of nonorthologous genes are induced in symbiosis. Of induced genes, 7-38% are orphan genes, including genes that encode secreted effector-like proteins. Convergent evolution of the mycorrhizal habit in fungi occurred via the repeated evolution of a 'symbiosis toolkit', with reduced numbers of PCWDEs and lineage-specific suites of mycorrhiza-induced genes