EndoPopulus: Endophyte Inoculation Enhances Populus Physiological Responses to Abiotic Stress
Darshi Banan1* (firstname.lastname@example.org), Jayde Aufrecht2, Sun Woo Chung1, Jun Hyuk Jeon1, Matt Hendrickson1, Sriram Parasurama1, Andrew Sher1, Robert Tournay1, Amirhossein Ahkami2, Soo-Hyung Kim1, and Sharon L. Doty1
1University of Washington; and 2Pacific Northwest National Laboratory
The overall goal of the EndoPopulus Project is to understand how, at a molecular level, the micro-organisms within the poplar tree microbiome can affect the host plant health and stress tolerance. The project will use a plant physiological approach to determine the impacts of endophyte inoculation on host plant performance under normal, nutrient-limited, and water-limited conditions. Data from field and greenhouse trials will be used to develop a process-based plant physiological model to generate testable hypotheses for further greenhouse examination of the microbial mechanisms responsible for altered plant productivity. Finally, physiological results will be integrated with microbiology, metabolomic, and transcriptomic data to generate an improved systems-level understanding of the plant-endophyte system scaling from the molecular to the canopy level.
Sustainable biofuel feedstock production is a key target for securing energy supply under climate change while minimizing environmental impacts. Inoculation with endophytes, mutualist microbes living inside plants, is a potential strategy to achieve this in forestry applications by improving host resource use efficiency, productivity, and stress tolerance. Endophytes isolated from trees in family Salicaceae have been shown to provide benefits such as fixing atmospheric nitrogen and synthesizing phytohormones in various in vitro and in planta experiments. Predicting how these benefits operate under production contexts requires a process-based understanding of plant, endophyte, and environmental interactions. This research investigates the physiological mechanisms by which inoculation with Salicaceae endophytes improves Populus performance under nutrient-limited or water-limited conditions.
Leaf epidermal morphology, photosynthesis, and whole-plant architecture and biomass were measured on native and hybrid poplars inoculated with Salicaceae endophytes in a series of greenhouse and field experiments. Experimental data were used to parameterize a coupled leaf gas exchange model to estimate the contribution of endophyte inoculation on biophysical and biochemical aspects of photosynthesis. Endophyte associated reductions in stomatal conductance varied with time of day and were most pronounced under higher light intensities. Likewise, improvements in photosynthetic water-use efficiency were greatest in inoculated plants under drought while inoculation reduced stomatal guard cell size regardless of water availability. Additionally, late season photosynthetic capacity (Vcmax and Jmax) was greater for inoculated plants under both greenhouse and field conditions. Under nitrogen-limited conditions, inoculated plants were taller and had root systems with greater total root length, branch number, and branching frequency compared to non-inoculated controls. These results suggest that the greatest benefits of endophyte inoculation on host productivity and resource use efficiency may be realized under stress conditions while other aspects of physiology, particularly stomatal morphology and photosynthesis, responded across a range of environments. A combination of microbiology, transcriptomic, and metabolomic approaches will be used to connect changes in plant physiology to endophyte diversity, abundance, and activity. Finally, process-based modeling will be used to scale these leaf- and plant-scale changes to the canopy scale to predict tree performance in biofuel feedstock production applications.
This research was supported by the DOE Office of Science, Biological and Environmental Research (BER) Program, grant no. DE-SC0021137.