COS 129-2 - THE IMPACT OF DIFFERENTIALLY EXPRESSED GENES IN MONOCLONAL AND POLYCLONAL PLANTINGS OF P. deltoides FOR AGRICULTURAL NITROGEN MITIGATION

Abstract: Excessive nitrogen run off from agricultural operations can cause the eutrophication of the Northern Gulf of Mexico. Nitrate (NO3-) contaminated groundwater and surface runoff from the southeast region of the United States flow into the lower Mississippi River Basin, causing excessive growth of algal blooms, hypoxic conditions, and deteriorates water quality. Populus deltoides planted in riparian areas could mitigate and intercept this excessive runoff. As an economically viable short rotation woody crop (SRWC), and a carbon neutral fuel, Populus deltoides can quickly produce large quantities of biomass and can easily be converted into biofuels to produce bioenergy. Polyclonal plantings of Populus spp. are expected to display an increase in site resource utilization, and growth and productivity through differentiated root system sorption zones (i.e. niche differentiation) and crown/canopy structures. This would increase the efficacy of Populus spp. ability to intercept and mitigate excessive nitrogen runoff. However, underlying molecular mechanisms of niche differentiation, including changes in site resource utilization and growth of polyclonal Populus plantings in the southeast region of the United States are poorly understood. We hypothesize that our two varieties of Populus deltoides in polyclonal plantings will show greater regulation of gene expression compared to our two varieties planted in monoclonal plantings. For this project, we will determine if differentially expressed genes (DEGs) are an underlying molecular mechanism of niche differentiation. This study will observe DEGs of Populus deltoides clones S7C8, 110412 and an even mixture of these two clones through mRNA-directional sequencing of leaf tissue during the second growing season. Early results from a Tukey’s HSD determines a significant decrease in mean nitrate concentrations of groundwater samples from the first to second growing seasons ((June 3^rd, 2021, µ=2.503, σ=.060) (July 25^th, 2022, µ=.249, σ=.004)). A differential expression analysis has identified higher expression of genes associated with the WRKY family transcription factor in polyclonal plantings (p< .001, FDR=0.019). A Gene Ontology and Kyoto Encyclopedia for Genomes and Genomics (KEGG) Enrichment Pathway analysis will follow to further elucidate genetic function and gene interaction in pathways of interest. A better understanding of molecular mechanisms involved in morphological and physiological variability in Populus deltoides could aid in developing genomic-based tools or approaches to better predict what combinations of varieties will provide the greatest growth, productivity and resource-use efficiency for future plantings.