Microbial endophytes of plants play important roles in providing nutrients to hosts, adapting hosts to their environments and defending them from biotic and abiotic stresses. In my lab we are exploring diversity of endophytes and the various impacts that they have on host plants. We are working to develop use of the clavicipitalean endophytes as a model system for understanding the evolution and dynamics of defensive mutualism. The host-symbiont interface in biotrophic endophytes is another area of interest. In particular, we are interested in understanding how endophytes induce plant hosts to release nutrients. Unlike most biotrophs, most endophytes do not possess haustoria or other specialized structures for nutrient absorption; and they do not penetrate or otherwise degrade host cells. Thus the mechanism by which nutrients are extracted from hosts is a mystery. Our current hypothesis regarding nutrient extraction from host cells involves secretion of reactive oxygen species (ROS) and auxins by endophytes onto host cell walls and membranes, inducing nutrient leakage from cells.
In another line of investigation we are investigating how plants use symbiotic, endophytic and epiphytic, diazotrophic microbes (bacteria or cyanobacteria) as nourishment for growth in soils that are low in nutrients; and how this process may impact on stress tolerance of hosts. In this research we have identified an oxidative process that plants may employ to obtain nutrients from symbiotic microbes. We term this process 'Oxidative Nitrogen Scavenging' (ONS). We hypothesize that plants in very extreme environments and at times of rapid growth of seedlings obtain scarce nutrients such as nitrogen through the oxidation/digestion of symbiotic (diazotrophic) bacteria. We are currently evaluating how widespread the process of ONS may be in plants; and we are conducting experiments to definitively prove ONS.