DISCOVERING HIDDEN DRIVERS OF RHIZOSPHERE SYMBIOSIS AND PARASITISM

This project will focus on the tripartite association between bacterial endosymbionts, plant-parasitic nematodes (PPNs), and plants, and determine how the endosymbionts functionally maintain their association by influencing PPN fitness and phenotype, therein impacting PPN-plant parasitism and ultimately plant functional responses to land use and climate change. Plant-parasitic nematodes are dominant animals in the rhizosphere that cause significant losses to crop yields and are extremely difficult to control. Yet, we recently discovered that they harbor bacterial endosymbionts that may have profound impacts on their PPN hosts, and therefore may be exciting targets for sustainable biocontrol. For example, we found a strain of Wolbachia (a-proteobacteria) - a bacteria used for biocontrol and vector control in mosquitoes - that may act as reproductive manipulator in PPNs. Similarly, we found a strain of Cardinium (Bacteroidetes) which likely confers similar reproductive manipulations through a different genetic mechanism. Our data suggests these PPN-endosymbiont associations may be ubiquitous in soils, yet, to date there has been no direct study of the function or distribution of these PPN endosymbionts.Project goals include both (1) research and (2) education, as follows: The research goal is to experimentally and bioinformatically assess the role of these widespread endosymbioses, to assess the overarching hypothesis that PPN endosymbionts represent overlooked 'missing-link' rhizosphere modulators that profoundly affect PPN parasitism, and therefore plant biology and ecology. To evaluate the specific mechanisms and impacts of these endosymbionts, we will use a systems biology approach, accomplished through three specific objectives: Objective 1: Determine the ecological and evolutionary forces acting on PPN endosymbiont function by analyzing signatures of selection across natural endosymbiont populations through (Obj. 1.1) analyzing population genomic data from field-sampled PPN populations for signatures of selection on hypothesized endosymbiont reproductive manipulator and nutrition provisioning genes, and (Obj. 1.2) analyzing drivers of evolution in these genes and others, across global populations of PPNs and rhizosphere samples through bioinformatic database mining. Objective 2: Directly test PPN endosymbiont effects on host nematode fitness, phenotype, and parasitism on plants using symbiont-clearing experiments by (Obj. 2.1) analyzing Wolbachia and Cardinium endosymbiont effects on PPNs using populations on root-cultures and measuring fitness and microbe-host gene expression, and using these lines (Obj. 2.2) for assessing endosymbiont effects on PPN parasitism on greenhouse plants with host plants and biospeckle assays in transparent soils. Objective 3: Evaluate and model the dual effects of PPN endosymbionts and environmental stress on PPN-plant community interactions through (Obj. 3.1) experimentally testing endosymbiont presence/absence effects on PPN parasitism in plant communities transplanted to the greenhouse under conditions of temperature stress; and (Obj. 3.2) developing and evaluating a computational model that probes endosymbiont-PPN-plant interactions under land-use and climate changes. The educational goal is to advance practical skill-development in diverse undergraduates, high school students, and in the community, through effective research-based learning that integrates interdisciplinary experiences and promotes scientific creativity. Educational objectives will be tightly integrated with research objectives through creating three specific programs: Education Objective 1: Create a "Bioinformatics Challenge" Undergraduate Fellowship. Computational and interdisciplinary education is increasingly important, and students seek more bioinformatics training. This proposed Bioinformatics Challenge Fellowship will test a flexible and responsive model of serving this need that will have students conduct problem-based hands-on experiential learning. It will strengthen the Biological Sciences department at Texas Tech University, which seeks to build its bioinformatics curriculum. Education Objective 2: Create a "Genomics Scholarship" peer-to-peer mentoring for high schoolers from underrepresented minorities. Our local community in Lubbock, West Texas, faces poverty and challenges, especially for traditionally underrepresented groups. Our solution to help students in these groups is through peer-mentoring of high schoolers by university students of similar backgrounds to build students' confidence and connection to their work by having them do original, hands-on research. Education Objective 3: Educate and integrate communities by developing pilot Rhizosphere Citizen Science and Rhizosphere Biomodelling Network programs. Citizen science is increasingly recognized and an exciting approach that increases public awareness of environmental and climate challenges. Similarly, social and grassroots networks of scientists and computer scientists are and exciting new direction for enhancing effective research and learning. Together, these voluntary approaches to public science can open new doors for people of diverse backgrounds and training.