As part of the Plant Microbes Interface project (pmi.ornl.gov), our primary objective is to understand how host plant genotype and environment interact with microbial members to shape community assembly and function. Populus spp. are known to associate with numerous microbes resulting in an assortment of functional interactions through known and yet to be discovered signaling and metabolic networks that drive neutral, antagonistic and mutualistic responses. Our efforts have identified systemic root-bacteria derived gene network that influences leaf metabolism, photosynthesis and whole plant fitness.