title: A common signaling process that promotes mycorrhizal and oomycete colonization of plants.
abstract: The symbiotic association between plants and arbuscular mycorrhizal fungi is almost ubiquitous within the plant kingdom, and the early stages of the association are controlled by plant-derived strigolactones acting as a signal to the fungus in the rhizosphere and lipochito-oligosaccharides acting as fungal signals to the plant. Hyphopodia form at the root surface, allowing the initial invasion, and this is analogous to appressoria, infection structures of pathogenic fungi and oomycetes. Here, we characterize RAM2, a gene of Medicago truncatula required for colonization of the root by mycorrhizal fungi, which is necessary for appropriate hyphopodia and arbuscule formation. RAM2 encodes a glycerol-3-phosphate acyl transferase (GPAT) and is involved in the production of cutin monomers. Plants defective in RAM2 are unable to be colonized by arbuscular mycorrhizal fungi but also show defects in colonization by an oomycete pathogen, with the absence of appressoria formation. RAM2 defines a direct signaling function, because exogenous addition of the C16 aliphatic fatty acids associated with cutin are sufficient to promote hyphopodia/appressoria formation. Thus, cutin monomers act as plant signals that promote colonization by arbuscular mycorrhizal fungi, and this signaling function has been recruited by pathogenic oomycetes to facilitate their own invasion.
authors.affiliation: Department of Disease and Stress Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK.
authors.forename: Ertao
authors.initials: E
authors.lastname: Wang
authors.forename: Sebastian
authors.initials: S
authors.lastname: Schornack
authors.forename: John F
authors.initials: JF
authors.lastname: Marsh
authors.forename: Enrico
authors.initials: E
authors.lastname: Gobbato
authors.forename: Benjamin
authors.initials: B
authors.lastname: Schwessinger
authors.forename: Peter
authors.initials: P
authors.lastname: Eastmond
authors.forename: Michael
authors.initials: M
authors.lastname: Schultze
authors.forename: Sophien
authors.initials: S
authors.lastname: Kamoun
authors.forename: Giles E D
authors.initials: GE
authors.lastname: Oldroyd
mesh_terms: D018506:Gene Expression Regulation, Plant; D005992:Glycerol-3-Phosphate O-Acyltransferase / Q000235:genetics* / Q000378:metabolism; D006790:Host-Parasite Interactions; D046913:Medicago truncatula / Q000201:enzymology / Q000235:genetics*; D008563:Membrane Lipids / Q000378:metabolism*; D008969:Molecular Sequence Data; D038821:Mycorrhizae / Q000502:physiology*; D009868:Oomycetes / Q000502:physiology*; D015398:Signal Transduction; D013559:Symbiosis
chemical_list: D008563:Membrane Lipids; C000521:cutin; D005992:Glycerol-3-Phosphate O-Acyltransferase