A new currency for mutualism? Fungal endophytes alter antioxidant activity in hosts responding to drought

Fungal endophytes have significant effects on host performance including but not limited to changes in reproductive output, as well as, biotic and abiotic stress tolerance. The ultimate mechanisms for resistance to herbivory have been documented in a number of fungal-plant symbiota and involve the production of alkaloids by the fungus. Alkaloids have thus been defined as a currency responsible for increased host resistance to herbivory. We provide support for the hypothesis that another currency may be responsible for increased host tolerance to abiotic stress resulting from endophyte colonization; namely antioxidants. We report comparatively higher activity of antioxidants in endophyte colonized hosts resulting from abiotic stress and propose antioxidants are another currency via which mutualistic interactions between fungal endophytes and their hosts can occur. We recognize fungal endophyte interactions are diverse and complex and include antagonisms, commensalisms, and mutualisms.