Bioprotective Alkaloids of Grass-Fungal Endophyte Symbioses

Symbiotic interactions of C3 grasses with fungal endophytes, Epichloe species and their asexual relatives Neotypkodium, often provide the grass hosts with major fitness enhancements (for review, see Siegel and Bush [1994]). The endophytes protect host plants from both biotic and abiotic environmental stresses. Documented enhancements to host fitness include greater resistance to mammalian and insect herbivores, pathogens, and nematodes, as well as increased drought tolerance and competitiveness. Our understanding of the mechanisms responsible for a11 of these effects on host fitness is not well established. However, the antiherbivore fitness enhancements are largely attributable to the accumulation of four groups of alkaloids: lolines, peramine, ergot alkaloids, and lolitrems. The objective of this Update is to present the current status of knowledge on these alkaloids, focusing on their biological activities and the potential for genetically manipulating their expression in grasslendophyte symbiota.