Plants roots inhabit soils containing diverse microorganisms, a subset of which can invade plant tissues to live as endophytes. Endophytic microbes range from pathogens to mutualists, yet how plants permit colonization by beneficial microbes while preventing exploitation by pathogens is not understood. Mutualistic plant-microbe interactions benefit hosts in numerous ways, including growth promotion, enhanced nutrient acquisition, and improved protection from pathogens. In light of these benefits, I am interested in how plant-endophyte interactions are influenced by host biotic and abiotic stresses. In particular, I am exploring how micronutrient (iron) deprivation affects colonization by beneficial fungal endophytes using the model plant Arabidopsis thaliana.