title: Intra and Inter-Spore Variability in Rhizophagus irregularis AOX Gene.
abstract: Arbuscular mycorrhizal fungi (AMF) are root-inhabiting fungi that form mutualistic symbioses with their host plants. AMF symbiosis improves nutrient uptake and buffers the plant against a diversity of stresses. Rhizophagus irregularis is one of the most widespread AMF species in the world, and its application in agricultural systems for yield improvement has increased over the last years. Still, from the inoculum production perspective, a lack of consistency of inoculum quality is referred to, which partially may be due to a high genetic variability of the fungus. The alternative oxidase (AOX) is an enzyme of the alternative respiratory chain already described in different taxa, including various fungi, which decreases the damage caused by oxidative stress. Nevertheless, virtually nothing is known on the involvement of AMF AOX on symbiosis establishment, as well on the existence of AOX variability that could affect AMF effectiveness and consequently plant performance. Here, we report the isolation and characterisation of the AOX gene of R. irregularis (RiAOX), and show that it is highly expressed during early phases of the symbiosis with plant roots. Phylogenetic analysis clustered RiAOX sequence with ancient fungi, and multiple sequence alignment revealed the lack of several regulatory motifs which are present in plant AOX. The analysis of RiAOX polymorphisms in single spores of three different isolates showed a reduced variability in one spore relatively to a group of spores. A high number of polymorphisms occurred in introns; nevertheless, some putative amino acid changes resulting from non-synonymous variants were found, offering a basis for selective pressure to occur within the populations. Given the AOX relatedness with stress responses, differences in gene variants amongst R. irregularis isolates are likely to be related with its origin and environmental constraints and might have a potential impact on inoculum production.
authors.affiliation: EU Marie Curie Chair, ICAAM-Instituto de Ciências Agrárias e Ambientais Mediterrânicas, IIFA-Instituto de Formação e Investigação Avançada, Universidade de Évora, Núcleo da Mitra, Évora, Portugal.
authors.forename: Catarina
authors.initials: C
authors.lastname: Campos
authors.affiliation: EU Marie Curie Chair, ICAAM-Instituto de Ciências Agrárias e Ambientais Mediterrânicas, IIFA-Instituto de Formação e Investigação Avançada, Universidade de Évora, Núcleo da Mitra, Évora, Portugal.
authors.forename: Hélia
authors.initials: H
authors.lastname: Cardoso
authors.affiliation: EU Marie Curie Chair, ICAAM-Instituto de Ciências Agrárias e Ambientais Mediterrânicas, IIFA-Instituto de Formação e Investigação Avançada, Universidade de Évora, Núcleo da Mitra, Évora, Portugal.
authors.forename: Amaia
authors.initials: A
authors.lastname: Nogales
authors.affiliation: Nordic Genetic Resource Center, Alnarp, Sweden.
authors.forename: Jan
authors.initials: J
authors.lastname: Svensson
authors.affiliation: Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas (EEZ-CSIC), Granada, Spain.
authors.forename: Juan Antonio
authors.initials: JA
authors.lastname: Lopez-Ráez
authors.affiliation: Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas (EEZ-CSIC), Granada, Spain.
authors.forename: María José
authors.initials: MJ
authors.lastname: Pozo
authors.affiliation: EU Marie Curie Chair, ICAAM-Instituto de Ciências Agrárias e Ambientais Mediterrânicas, IIFA-Instituto de Formação e Investigação Avançada, Universidade de Évora, Núcleo da Mitra, Évora, Portugal.
authors.forename: Tânia
authors.initials: T
authors.lastname: Nobre
authors.affiliation: Inoq GmbH, Solkau, Schnega, Germany.
authors.forename: Carolin
authors.initials: C
authors.lastname: Schneider
authors.affiliation: EU Marie Curie Chair, ICAAM-Instituto de Ciências Agrárias e Ambientais Mediterrânicas, IIFA-Instituto de Formação e Investigação Avançada, Universidade de Évora, Núcleo da Mitra, Évora, Portugal.
authors.forename: Birgit
authors.initials: B
authors.lastname: Arnholdt-Schmitt
mesh_terms: D024101:Mitochondrial Proteins / Q000235:genetics*; D038821:Mycorrhizae / Q000235:genetics*; D010088:Oxidoreductases / Q000235:genetics*; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics*; D018517:Plant Roots / Q000235:genetics / Q000382:microbiology; D010944:Plants / Q000235:genetics* / Q000382:microbiology*; D013172:Spores, Fungal / Q000235:genetics*; D013559:Symbiosis / Q000235:genetics; D000099188:Alternative Oxidase
chemical_list: D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D010940:Plant Proteins; D000099188:Alternative Oxidase