Molecular biology of Epichloe endophyte toxin biosynthesis

Abstract

Epichloë endophytes are an important group of filamentous fungi that confer on the grass host a range of biological benefits. However, endophyte synthesis of ergopeptine and indole-diterpene mammalian toxins in pasture grasses is detrimental to livestock grazing on that forage. The molecular cloning of the genes involved in the biosynthesis of these toxins will enhance our ability to maximise the beneficial attributes of this mutualistic association through the availability of DNA probes to screen and select for desirable endophytes and through our ability to genetically modify endophytes. Genes involved in the biosynthesis of both classes of alkaloids have recently been cloned from Claviceps purpurea and Penicillium paxilli. In both cases the genes are organised in large clusters; a feature that will facilitate a complete genetic analysis of each pathway and provide probes for isolating homologous genes from Epichloë endophytes. This paper reviews recent research developments on the molecular biology of these two pathways. Keywords: Epichloë endophytes, ergopeptines, gene cloning, gene manipulation, indole-diterpenes