title: A novel family of cyclic oligopeptides derived from ribosomal peptide synthesis of an in planta-induced gene, gigA, in Epichloë endophytes of grasses.
abstract: Fungal endophytes belonging to the genus Epichloë form associations with temperate grasses belonging to the sub-family Poöideae that range from mutualistic through to pathogenic. We previously identified a novel endophyte gene (designated gigA for grass induced gene) that is one of the most abundantly expressed fungal transcripts in endophyte-infected grasses and which is distributed and highly expressed in a wide range of Epichloë grass associations. Molecular and biochemical analyses indicate that gigA encodes a small secreted protein containing an imperfect 27 amino acid repeat that includes a kexin protease cleavage site. Kexin processing of GigA liberates within the plant multiple related products, named here as epichloëcyclins, which we have demonstrated by MS/MS to be cyclic peptidic in nature. Gene deletion of gigA leads to the elimination of all epichloëcyclins with no conspicuous phenotypic impact on the host grass, suggesting a possible bioactive role. This is a further example of a ribosomal peptide synthetic (RiPS) pathway operating within the Ascomycetes, and is the first description of such a pathway from a mutualistic symbiotic fungus from this Phylum.
authors.affiliation: AgResearch, Grasslands Research Centre, Tennent Drive, Private Bag 11008, Palmerston North, New Zealand. Electronic address: richard.johnson@agresearch.co.nz.
authors.forename: Richard D
authors.initials: RD
authors.lastname: Johnson
authors.affiliation: AgResearch, Grasslands Research Centre, Tennent Drive, Private Bag 11008, Palmerston North, New Zealand.
authors.forename: Geoffrey A
authors.initials: GA
authors.lastname: Lane
authors.affiliation: AgResearch, Grasslands Research Centre, Tennent Drive, Private Bag 11008, Palmerston North, New Zealand.
authors.forename: Albert
authors.initials: A
authors.lastname: Koulman
authors.affiliation: AgResearch, Grasslands Research Centre, Tennent Drive, Private Bag 11008, Palmerston North, New Zealand.
authors.forename: Mingshu
authors.initials: M
authors.lastname: Cao
authors.affiliation: AgResearch, Grasslands Research Centre, Tennent Drive, Private Bag 11008, Palmerston North, New Zealand.
authors.forename: Karl
authors.initials: K
authors.lastname: Fraser
authors.affiliation: AgResearch, Grasslands Research Centre, Tennent Drive, Private Bag 11008, Palmerston North, New Zealand.
authors.forename: Damien J
authors.initials: DJ
authors.lastname: Fleetwood
authors.affiliation: AgResearch, Grasslands Research Centre, Tennent Drive, Private Bag 11008, Palmerston North, New Zealand.
authors.forename: Christine R
authors.initials: CR
authors.lastname: Voisey
authors.affiliation: AgResearch, Lincoln Research Centre, Cnr Springs Road and Gerald Street, Private Bag 4749, Christchurch, New Zealand.
authors.forename: Jolon M
authors.initials: JM
authors.lastname: Dyer
authors.affiliation: AgResearch, Grasslands Research Centre, Tennent Drive, Private Bag 11008, Palmerston North, New Zealand.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Pratt
authors.affiliation: AgResearch, Grasslands Research Centre, Tennent Drive, Private Bag 11008, Palmerston North, New Zealand.
authors.forename: Michael
authors.initials: M
authors.lastname: Christensen
authors.affiliation: AgResearch, Grasslands Research Centre, Tennent Drive, Private Bag 11008, Palmerston North, New Zealand.
authors.forename: Wayne R
authors.initials: WR
authors.lastname: Simpson
authors.affiliation: AgResearch, Grasslands Research Centre, Tennent Drive, Private Bag 11008, Palmerston North, New Zealand.
authors.forename: Gregory T
authors.initials: GT
authors.lastname: Bryan
authors.affiliation: AgResearch, Grasslands Research Centre, Tennent Drive, Private Bag 11008, Palmerston North, New Zealand.
authors.forename: Linda J
authors.initials: LJ
authors.lastname: Johnson
mesh_terms: D060026:Endophytes / Q000235:genetics* / Q000502:physiology; D055329:Epichloe / Q000235:genetics* / Q000502:physiology; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D009842:Oligopeptides / Q000235:genetics / Q000378:metabolism; D010456:Peptides, Cyclic / Q000235:genetics / Q000378:metabolism; D006109:Poaceae / Q000382:microbiology*; D014176:Protein Biosynthesis; D012269:Ribosomal Proteins / Q000737:chemistry / Q000378:metabolism; D013559:Symbiosis; D053719:Tandem Mass Spectrometry
chemical_list: D005656:Fungal Proteins; D009842:Oligopeptides; D010456:Peptides, Cyclic; D012269:Ribosomal Proteins
keywords: Cyclic oligopeptide; Epichloë; Epichloëcyclin; Ribosomal peptide synthetic pathway; Symbiosis