Transcriptional Reprogramming of Defence Pathways by the Entomopathogen Correlates With Resistance Against a Fungal Pathogen but Not Against Insects.

The entomopathogenic fungus can adopt an endophytic lifestyle by colonising a wide array of plant species. -colonised plants can show enhanced resistance against insects and plant pathogens alike. However, little is known about the molecular and physiological mechanisms that govern such interactions. Here, we assessed the effects of two strains (BG11, FRh2) on the growth of and its resistance against two herbivore species and a phytopathogen. Plant responses were studied on the transcriptomic and metabolic level using microarrays and by measuring changes in defence-related phytohormones and glucosinolates (GLSs). Root inoculation with BG11 significantly increased plant growth, while FRh2 had no such effect. Both strains decreased leaf lesion area caused by the phytopathogen but did not affect population growth of the aphid or the growth of caterpillars. Microarray analyses of leaves from endophyte-inoculated provided evidence for transcriptional reprogramming of plant defence pathways, with strain-specific changes in the expression of genes related to pathogenesis, phytoalexin, jasmonic (JA), and salicylic acid (SA) signalling pathways. However, colonisation did not result in higher concentrations of JA and SA or major changes in leaf GLS profiles. We conclude that the endophyte induces plant defence responses and hypothesise that these contribute to enhanced resistance against .