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Neotyphodium is a genus containing species of fungal obligate endophytes. They are asexual, seed-borne intercellular symbionts of cool-season grass colonizing the aerial (leaves and stems) tissues of their grass hosts.[1] Neotyphodium species are closely related to teleomorphic species of the genus Epichloë from which they have evolved by processes involving interspecific hybridization.[2] While being obligate symbionts in nature, most Neotyphodium species are readily culturable in the laboratory on culture media containing, e.g., potato dextrose broth.
Evolutionary theory predicts that asexual symbionts should be strong mutualists since their reproductive fitness is intimately tied to that of its host. In fact, some positive effects of Neotyphodium infection on its host plant include increased growth, drought tolerance, and herbivore and pathogen resistance. Resistance against herbivores has been attributed to endophyte-produced alkaloids[3]. These alkaloids include ergot alkaloids, such as ergovaline (comprised of an ergoline moiety, attached to a tripeptide, containing the amino acids, L-proline, L-alanine, and L-valine), and indole-diterpenoids, such as lolitrem B [3]. Both of these alkaloid classes have biological activity against mammalian herbivores, and also activity against some insects. Peramine (a pyrrolopyrazine alkaloid, biosynthesized by Neotyphodium fungi from the amino acids L-proline (or a derivative thereof) and L-arginine [4]) is an insect-feeding deterrent, and 1-aminopyrrolizidines (common name, "lolines", which are biosynthesized from the amino acids, L-proline and L-homoserine [5])) are insecticidal and insect-deterrent alkaloids. Many, but not all, Neotyphodium species produce up to three classes of these alkaloids. Although this grass-endophyte association has been widely recognized to be mutualistic in a few agronomic grasses, the direction of the interaction found in native grasses is highly variable and sometimes antagonistic, especially under nutrient-poor conditions.
[edit] Species
- Neotyphodium aotearoae
- Neotyphodium chilense
- Neotyphodium chisosum
- Neotyphodium coenophialum
- Neotyphodium huerfanum
- Neotyphodium lolii
- Neotyphodium occultans
- Neotyphodium starrii
- Neotyphodium tembladerae
- Neotyphodium typhinum
- Neotyphodium uncinatum
[edit] References
- ^ Roberts CA, West CP, Spiers DE, eds (2005). Neotyphodium in Cool-Season Grasses. Blackwell. ISBN 978-0813801896.
- ^ Tsai HF, Liu JS, Staben C, Christensen MJ, Latch GC, Siegel MR, Schardl CL (1994). "Evolutionary diversification of fungal endophytes of tall fescue grass by hybridization with Epichloë species". Proc. Natl. Acad. Sci. USA 91: 2542-2546. PMID 8172623.
- ^ a b Bush LP, Wilkinson HH, Schardl CL (1997). "Bioprotective Alkaloids of Grass-Fungal Endophyte Symbioses". Plant Physiol. 114: 1-7. PMID 12223685.
- ^ Tanaka A, Tapper BA, Popay A, Parker, EJ, Scott B (2005). "A symbiosis expressed non-ribosomal peptide synthetase from a mutualistic fungal endophyte of perennial ryegrass confers protection to the symbiotum from insect herbivory". Mol. Microbiol. 57: 1036-1050. PMID 16091042.
- ^ Blankenship JD, Houseknecht JB, Pal S, Bush LP, Grossman RB, Schardl CL (2005). "Biosynthetic precursors of fungal pyrrolizidines, the loline alkaloids". Chembiochem 6: 1016-1022. PMID 15861432.
