title: A complex gene cluster for indole-diterpene biosynthesis in the grass endophyte Neotyphodium lolii.
abstract: Lolitrems are a structurally diverse group of indole-diterpene mycotoxins synthesized by Epichloë/Neotyphodium endophytes in association with Pooid grasses. Using suppression subtractive hybridization combined with chromosome walking, two clusters of genes for lolitrem biosynthesis were isolated from Neotyphodium lolii, a mutualistic endophyte of perennial ryegrass. The first cluster contains five genes, ltmP, ltmQ, ltmF, ltmC, and ltmB, four of which appear to be orthologues of functionally characterized genes from Penicillium paxilli. The second cluster contains two genes, ltmE and ltmJ, that appear to be unique to lolitrem biosynthesis. The two clusters are separated by a 16 kb AT-rich sequence that includes two imperfect direct repeats. A previously isolated ltm cluster composed of ltmG, ltmM, and ltmK, is linked to these two new clusters by 35 kb of AT-rich retrotransposon relic sequence. All 10 genes at this complex LTM locus were highly expressed in planta but expression was very low or undetectable in mycelia. ltmM and ltmC were shown to be functional orthologues of P. paxilli paxM and paxC, respectively. This work provides a genetic foundation for elucidating the metabolic grid responsible for the diversity of indole-diterpenes synthesized by N. lolii.
authors.affiliation: Centre for Functional Genomics, Institute of Molecular BioSciences, Massey University, Private Bag 11222, Palmerston North, New Zealand.
authors.forename: Carolyn A
authors.initials: CA
authors.lastname: Young
authors.forename: Silvina
authors.initials: S
authors.lastname: Felitti
authors.forename: Katherine
authors.initials: K
authors.lastname: Shields
authors.forename: German
authors.initials: G
authors.lastname: Spangenberg
authors.forename: Richard D
authors.initials: RD
authors.lastname: Johnson
authors.forename: Gregory T
authors.initials: GT
authors.lastname: Bryan
authors.forename: Sanjay
authors.initials: S
authors.lastname: Saikia
authors.forename: Barry
authors.initials: B
authors.lastname: Scott
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods; D002874:Chromosome Mapping / Q000379:methods; D019295:Computational Biology; D004224:Diterpenes / Q000737:chemistry / Q000378:metabolism*; D020224:Expressed Sequence Tags; D015966:Gene Expression Regulation, Fungal / Q000235:genetics; D005800:Genes, Fungal / Q000235:genetics; D006999:Hypocreales / Q000235:genetics* / Q000378:metabolism; D007211:Indoles / Q000737:chemistry / Q000378:metabolism; D008129:Lolium / Q000737:chemistry / Q000382:microbiology*; D008969:Molecular Sequence Data; D015394:Molecular Structure; D005810:Multigene Family / Q000235:genetics*; D009183:Mycotoxins / Q000737:chemistry / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D013559:Symbiosis / Q000235:genetics
chemical_list: D004224:Diterpenes; D007211:Indoles; D009183:Mycotoxins; D012333:RNA, Messenger; C048221:paspaline; C048220:paxilline