Gene discovery and microarray-based transcriptome analysis of the grass-endophyte association

SPANGENBERG, G.C.; FELITTI, S.A.; SHIELDS, K.; RAMSPERGER, M.; TIAN, P.; ONG, E.K.; SINGH, D.; LOGAN, E.; EDWARDS, D.

Neotyphodium in cool-season grasses

Blackwell Publishing

Lugar: Iowa; Año: 2005; p. 103 - 121

Neotyphodium lolii, N. coenophialum, and Epichloë festucae are common symbiotic fungal endophytes of the temperate pasture grasses perennial ryegrass (Lolium perenne), tall fescue (Festuca arundinacea), and red fescue (Festuca rubra), respectively (Christensen et al., 1993). Epichloë taxa are ascomycete fungi (family Clavicipitaceae) that are ecologicaly obligate symbionts of grasses (Schardl et al., 1997). They comprise both the sexual Epichloë species and their asexual Neotyphodium derivatives (Glenn et al. 1996; Schardl, 1996). All establish asymptomatic associations with their host during the vegetative phase of growth, but the sexual species are capable of forming a stroma around the developing inflorescence that partially of completely blocks emergence of the floral meristem. Relative mutualism or antagonism of an Epichloë-grass symbiosis is largely related to the path fo symbiont transmission (Schardl et al., 1997). Many of these fungi can propagate clonally in the floral meristems and consequently in the seed progeny of infected mother plants (vertical or matrilinear transmission). Alternatively, genotypes can transmit horizontally via sexual spores in a life cycle that also requires a third symbiont (the fly Phorbia phrenione) to mediate fungal mating (Schardl et al., 1997). The benefits of the symbiosis for the host are increased seedling vigor and persistence and drought tolerance in marginal environments (Elbersen and West, 1996; Hill et al., 1990; Malinowski and Belesky, 1999). It also provides protection against some insect pests and nematodes (Breen, 1993; Elmi et al., 2000; Prestidge and Gallagher, 1988). Specific metabolites produced by the endophyte such as peramine and loline alkaloids provide protection from insect pests (Rowan and Gaynor, 1986; Wilkinson et al., 2000). However, other metabolites such as lolitrem B and ergovaline are toxis to grazing animals, causing conditions known as ryegrass staggers and fescue toxicosis, respectively (Gallagher et al., 1984; Yates et al., 1985). The most thoroughly studied compounds are alkaloids, including ergopeptine alkaloids, indole-isoprenoid lolitrems, pyrrolizidine alkaloids, and pyrrolopyrazyne alkaloids (Bush et al., 1997; Scott, 2001).