title: Genome of an arbuscular mycorrhizal fungus provides insight into the oldest plant symbiosis.
abstract: The mutualistic symbiosis involving Glomeromycota, a distinctive phylum of early diverging Fungi, is widely hypothesized to have promoted the evolution of land plants during the middle Paleozoic. These arbuscular mycorrhizal fungi (AMF) perform vital functions in the phosphorus cycle that are fundamental to sustainable crop plant productivity. The unusual biological features of AMF have long fascinated evolutionary biologists. The coenocytic hyphae host a community of hundreds of nuclei and reproduce clonally through large multinucleated spores. It has been suggested that the AMF maintain a stable assemblage of several different genomes during the life cycle, but this genomic organization has been questioned. Here we introduce the 153-Mb haploid genome of Rhizophagus irregularis and its repertoire of 28,232 genes. The observed low level of genome polymorphism (0.43 SNP per kb) is not consistent with the occurrence of multiple, highly diverged genomes. The expansion of mating-related genes suggests the existence of cryptic sex-related processes. A comparison of gene categories confirms that R. irregularis is close to the Mucoromycotina. The AMF obligate biotrophy is not explained by genome erosion or any related loss of metabolic complexity in central metabolism, but is marked by a lack of genes encoding plant cell wall-degrading enzymes and of genes involved in toxin and thiamine synthesis. A battery of mycorrhiza-induced secreted proteins is expressed in symbiotic tissues. The present comprehensive repertoire of R. irregularis genes provides a basis for future research on symbiosis-related mechanisms in Glomeromycota.
authors.affiliation: Institut National de la Recherche Agronomique, Unité Mixte de Recherche 1136, Interactions Arbres/Microorganismes, Centre de Nancy, Université de Lorraine, 54280 Champenoux, France.
authors.forename: Emilie
authors.initials: E
authors.lastname: Tisserant
authors.forename: Mathilde
authors.initials: M
authors.lastname: Malbreil
authors.forename: Alan
authors.initials: A
authors.lastname: Kuo
authors.forename: Annegret
authors.initials: A
authors.lastname: Kohler
authors.forename: Aikaterini
authors.initials: A
authors.lastname: Symeonidi
authors.forename: Raffaella
authors.initials: R
authors.lastname: Balestrini
authors.forename: Philippe
authors.initials: P
authors.lastname: Charron
authors.forename: Nina
authors.initials: N
authors.lastname: Duensing
authors.forename: Nicolas
authors.initials: N
authors.lastname: Frei dit Frey
authors.forename: Vivienne
authors.initials: V
authors.lastname: Gianinazzi-Pearson
authors.forename: Luz B
authors.initials: LB
authors.lastname: Gilbert
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Handa
authors.forename: Joshua R
authors.initials: JR
authors.lastname: Herr
authors.forename: Mohamed
authors.initials: M
authors.lastname: Hijri
authors.forename: Raman
authors.initials: R
authors.lastname: Koul
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Kawaguchi
authors.forename: Franziska
authors.initials: F
authors.lastname: Krajinski
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Lammers
authors.forename: Frederic G
authors.initials: FG
authors.lastname: Masclaux
authors.forename: Claude
authors.initials: C
authors.lastname: Murat
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Morin
authors.forename: Steve
authors.initials: S
authors.lastname: Ndikumana
authors.forename: Marco
authors.initials: M
authors.lastname: Pagni
authors.forename: Denis
authors.initials: D
authors.lastname: Petitpierre
authors.forename: Natalia
authors.initials: N
authors.lastname: Requena
authors.forename: Pawel
authors.initials: P
authors.lastname: Rosikiewicz
authors.forename: Rohan
authors.initials: R
authors.lastname: Riley
authors.forename: Katsuharu
authors.initials: K
authors.lastname: Saito
authors.forename: Hélène
authors.initials: H
authors.lastname: San Clemente
authors.forename: Harris
authors.initials: H
authors.lastname: Shapiro
authors.forename: Diederik
authors.initials: D
authors.lastname: van Tuinen
authors.forename: Guillaume
authors.initials: G
authors.lastname: Bécard
authors.forename: Paola
authors.initials: P
authors.lastname: Bonfante
authors.forename: Uta
authors.initials: U
authors.lastname: Paszkowski
authors.forename: Yair Y
authors.initials: YY
authors.lastname: Shachar-Hill
authors.forename: Gerald A
authors.initials: GA
authors.lastname: Tuskan
authors.forename: J Peter W
authors.initials: JP
authors.lastname: Young
authors.forename: Peter W
authors.initials: PW
authors.lastname: Young
authors.forename: Ian R
authors.initials: IR
authors.lastname: Sanders
authors.forename: Bernard
authors.initials: B
authors.lastname: Henrissat
authors.forename: Stefan A
authors.initials: SA
authors.lastname: Rensing
authors.forename: Igor V
authors.initials: IV
authors.lastname: Grigoriev
authors.forename: Nicolas
authors.initials: N
authors.lastname: Corradi
authors.forename: Christophe
authors.initials: C
authors.lastname: Roux
authors.forename: Francis
authors.initials: F
authors.lastname: Martin
mesh_terms: D001483:Base Sequence; D019143:Evolution, Molecular; D016681:Genome, Fungal / Q000235:genetics*; D055137:Glomeromycota / Q000235:genetics*; D008969:Molecular Sequence Data; D038821:Mycorrhizae / Q000235:genetics*; D010944:Plants / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D013559:Symbiosis / Q000235:genetics*
keywords: carbohydrate-active enzymes; effector; fungal evolution; glomales; mutualism