title: RiPEIP1, a gene from the arbuscular mycorrhizal fungus Rhizophagus irregularis, is preferentially expressed in planta and may be involved in root colonization.
abstract: Transcriptomics and genomics data recently obtained from the arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis have offered new opportunities to decipher the contribution of the fungal partner to the establishment of the symbiotic association. The large number of genes which do not show similarity to known proteins witnesses the uniqueness of this group of plant-associated fungi. In this work, we characterize a gene that was called RiPEIP1 (Preferentially Expressed In Planta). Its expression is strongly induced in the intraradical phase, including arbuscules, and follows the expression profile of the Medicago truncatula phosphate transporter MtPT4, a molecular marker of a functional symbiosis. Indeed, mtpt4 mutant plants, which exhibit low mycorrhizal colonization and an accelerated arbuscule turnover, also show a reduced RiPEIP1 mRNA abundance. To further characterize RiPEIP1, in the absence of genetic transformation protocols for AM fungi, we took advantage of two different fungal heterologous systems. When expressed as a GFP fusion in yeast cells, RiPEIP1 localizes in the endomembrane system, in particular to the endoplasmic reticulum, which is consistent with the in silico prediction of four transmembrane domains. We then generated RiPEIP1-expressing strains of the fungus Oidiodendron maius, ericoid endomycorrhizal fungus for which transformation protocols are available. Roots of Vaccinium myrtillus colonized by RiPEIP1-expressing transgenic strains showed a higher mycorrhization level compared to roots colonized by the O. maius wild-type strain, suggesting that RiPEIP1 may regulate the root colonization process.
authors.affiliation: Department of Life Science and Systems Biology, University of Torino, via Accademia Albertina 13, 10123, Torino, Italy. valentina.fiorilli@unito.it.
authors.forename: Valentina
authors.initials: V
authors.lastname: Fiorilli
authors.affiliation: Department of Life Science and Systems Biology, University of Torino, via Accademia Albertina 13, 10123, Torino, Italy.
authors.forename: Simone
authors.initials: S
authors.lastname: Belmondo
authors.affiliation: Department of Life Science and Systems Biology, University of Torino, via Accademia Albertina 13, 10123, Torino, Italy.
authors.forename: Hassine Radhouane
authors.initials: HR
authors.lastname: Khouja
authors.affiliation: Institute for Sustainable Plant Protection (IPSP), CNR, Strada delle Cacce 73, 10135, Torino, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Abbà
authors.affiliation: Institute for Sustainable Plant Protection (IPSP), CNR, Strada delle Cacce 73, 10135, Torino, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Faccio
authors.affiliation: Department of Life Science and Systems Biology, University of Torino, via Accademia Albertina 13, 10123, Torino, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Daghino
authors.affiliation: Department of Life Science and Systems Biology, University of Torino, via Accademia Albertina 13, 10123, Torino, Italy.
authors.forename: Luisa
authors.initials: L
authors.lastname: Lanfranco
mesh_terms: D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal / Q000502:physiology*; D055137:Glomeromycota / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D046913:Medicago truncatula / Q000382:microbiology*; D038821:Mycorrhizae / Q000235:genetics* / Q000378:metabolism*; D018517:Plant Roots / Q000382:microbiology; D015003:Yeasts / Q000235:genetics / Q000378:metabolism
chemical_list: D005656:Fungal Proteins; D049452:Green Fluorescent Proteins
keywords: Arbuscular mycorrhizal symbiosis; Heterologous expression system; Oidiodendron maius; Rhizophagus irregularis