title: A GRAS-type transcription factor with a specific function in mycorrhizal signaling.
abstract: Legumes establish mutualistic associations with mycorrhizal fungi and with nitrogen-fixing rhizobial bacteria. These interactions occur following plant recognition of Nod factor from rhizobial bacteria and Myc factor from mycorrhizal fungi. A common symbiosis signaling pathway is involved in the recognition of both Nod factor and Myc factor and is required for the establishment of these two symbioses. The outcomes of these associations differ, and therefore, despite the commonality in signaling, there must be mechanisms that allow specificity. In Nod factor signaling, a complex of GRAS-domain transcription factors controls gene expression downstream of the symbiosis signaling pathway. Here, we show that a GRAS-domain transcription factor, RAM1, functions in mycorrhizal-specific signaling. Plants mutated in RAM1 are unable to be colonized by mycorrhizal fungi, with a defect in hyphopodia formation on the surface of the root. RAM1 is specifically required for Myc factor signaling and appears to have no role in Nod factor signaling. RAM1 regulates the expression of RAM2, a glycerol-3-phosphate acyl transferase that promotes cutin biosynthesis to enhance hyphopodia formation. We conclude that mycorrhizal signaling downstream of the symbiosis-signaling pathway has parallels with nodulation-specific signaling and functions to promote mycorrhizal colonization by regulating cutin biosynthesis.
authors.affiliation: John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK.
authors.forename: Enrico
authors.initials: E
authors.lastname: Gobbato
authors.forename: John F
authors.initials: JF
authors.lastname: Marsh
authors.forename: Tatiana
authors.initials: T
authors.lastname: Vernié
authors.forename: Ertao
authors.initials: E
authors.lastname: Wang
authors.forename: Fabienne
authors.initials: F
authors.lastname: Maillet
authors.forename: Jiyoung
authors.initials: J
authors.lastname: Kim
authors.forename: J Benjamin
authors.initials: JB
authors.lastname: Miller
authors.forename: Jongho
authors.initials: J
authors.lastname: Sun
authors.forename: S Asma
authors.initials: SA
authors.lastname: Bano
authors.forename: Pascal
authors.initials: P
authors.lastname: Ratet
authors.forename: Kirankumar S
authors.initials: KS
authors.lastname: Mysore
authors.forename: Jean
authors.initials: J
authors.lastname: Dénarié
authors.forename: Michael
authors.initials: M
authors.lastname: Schultze
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*; D008563:Membrane Lipids / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D038821:Mycorrhizae / Q000502:physiology*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D055170:Plant Root Nodulation; D015398:Signal Transduction; D013559:Symbiosis; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D008563:Membrane Lipids; D010940:Plant Proteins; D014157:Transcription Factors; C000521:cutin; D005992:Glycerol-3-Phosphate O-Acyltransferase