Plant responses to endophytic fungi and their effects on herbivorous insects

Abstract

Communities of fungal endophytes are ubiquitous in above and below-ground tissues of probably all plants, where they live without causing any visible symptoms. Endophytes and plants have been found to interact on the molecular and biochemical level and, depending on the fungal species (or isolate) involved, the outcome of such interactions may even be beneficial to the colonized plant, leading to enhanced growth and stress tolerance. Plants and herbivorous insects also form intricate relationships and because plant chemistry is crucial for herbivore development and behaviour, endophyte-mediated responses may change the outcome of such plant-insect interactions. To shed some light on this question we studied the plant responses to three endophyte species with significantly different life histories: a ubiquitous, facultative root-colonizer (Trichoderma atroviride), a well-known insect pathogen (Beauveria bassiana), which was only recently described as capable of endophytic colonization, and the obligate shoot-colonizing grass endophyte Epichloë uncinatum. This talk will highlight some of the metabolic and transcriptional changes each fungus causes and will focus on the possible induction of plant defences against insects. Furthermore, data will be presented that demonstrate changes in volatile root compounds due to endophyte colonization and how this can affect the foraging behaviour of a soil insect. We conclude that endophytes interact directly with plants and indirectly with higher trophic levels thus playing important roles in the ecosystem. Understanding the mechanisms of these multitrophic interactions may help to manipulate crop plants for more sustainable pest and pathogen management.