title: Expanding genomics of mycorrhizal symbiosis.
abstract: The mycorrhizal symbiosis between soil fungi and plant roots is a ubiquitous mutualism that plays key roles in plant nutrition, soil health, and carbon cycling. The symbiosis evolved repeatedly and independently as multiple morphotypes [e.g., arbuscular mycorrhizae (AM), ectomycorrhizal (ECM)] in multiple fungal clades (e.g., phyla Glomeromycota, Ascomycota, Basidiomycota). The accessibility and cultivability of many mycorrhizal partners make them ideal models for symbiosis studies. Alongside molecular, physiological, and ecological investigations, sequencing led to the first three mycorrhizal fungal genomes, representing two morphotypes and three phyla. The genome of the ECM basidiomycete Laccaria bicolor showed that the mycorrhizal lifestyle can evolve through loss of plant cell wall-degrading enzymes (PCWDEs) and expansion of lineage-specific gene families such as short secreted protein (SSP) effectors. The genome of the ECM ascomycete Tuber melanosporum showed that the ECM type can evolve without expansion of families as in Laccaria, and thus a different set of symbiosis genes. The genome of the AM glomeromycete Rhizophagus irregularis showed that despite enormous phylogenetic distance and morphological difference from the other two fungi, symbiosis can involve similar solutions as symbiosis-induced SSPs and loss of PCWDEs. The three genomes provide a solid base for addressing fundamental questions about the nature and role of a vital mutualism.
authors.affiliation: United States Department of Energy Joint Genome Institute Walnut Creek, CA, USA.
authors.forename: Alan
authors.initials: A
authors.lastname: Kuo
authors.affiliation: UMR, Lab of Excellence for Advanced Research on the Biology of TRee and Forest Ecosystems, Tree-Microbe Interactions, Institut National de la Recherche Agronomique, Université de Lorraine Nancy, France.
authors.forename: Annegret
authors.initials: A
authors.lastname: Kohler
authors.affiliation: UMR, Lab of Excellence for Advanced Research on the Biology of TRee and Forest Ecosystems, Tree-Microbe Interactions, Institut National de la Recherche Agronomique, Université de Lorraine Nancy, France.
authors.forename: Francis M
authors.initials: FM
authors.lastname: Martin
authors.affiliation: United States Department of Energy Joint Genome Institute Walnut Creek, CA, USA.
authors.forename: Igor V
authors.initials: IV
authors.lastname: Grigoriev
keywords: Glomus; Laccaria; Rhizophagus; Tuber; mycorrhizae