Performing Department
Soil Science
Non Technical Summary
Bacteria of the genus Acidovorax are pathogens of plants important in food production and bioenergy development, as well as in the ornamental and turf industries. While Acidovorax-related diseases have a broad impact, relatively little is known about the biology of phytopathogenic Acidovorax, and mechanisms underlying virulence are unestablished. Recently, the Principle Investigator identified a previously unrecognized characteristic common to phytopathogenic Acidovorax species, namely that all possess a unique surface layer protein. This is significant, as the surface layer (S-layer) would be the predominant exterior thus be important in virulence-related extracellular interactions. Furthermore, the S-layer enables development of novel structures discovered by the Principle Investigator, called nanopods, which are S-layer extensions that contain outer membrane vesicles. Outer membrane vesicles (OMV) have been studied extensively in bacterial human pathogens and play a key role in disease development by transmitting virulence determinants. For phytopathogens such as Pseudomonas syringae and Xanthomonas campestris, OMV are also now gaining recognition as having similarly important roles in disease. For phytopathogenic Acidovorax, the role of OMV in virulence has not been assessed. This project will examine the role of these newly discovered structures (the S-layer and nanopods) in the biology and virulence of Acidovorax. The findings could provide new insights to mechansims important in the Acidovorax-plant interactions, which might facilitate development of strategies to mitigate crop damage caused by this important group of pathogens.Molecular genetics approaches will be used in laboratory studies to manipulate the capacity of Acidovorax to produce specific proteins. The effect that these manipulations have upon the ability of mutant Acidovorax to cause disease will then be tested in the laboratory by injecting bacterial cells into watermelon fruit. Results will be compared to watermelon injected with natural Acidovorax, which causes severe decomposition of the fruit in a peroid of about three weeks. If the mutations affect virulence, disease symptoms should be either absent or significantly reduced compared to those observed with natural Acidovorax. Findings from the studies will be communicated in research journals, conferences and through social media. The ultimate goal is to determine if the S-layer and/or OMV play roles in the virulence of Acidovorax. If results from these experiments confirm such functions, it will have the immediate effect of opening a new dimension to the research field about bacterial plant pathogens. A longer term impact could be the develpment of new strategies to prevent or remediate outbreakes of plant diseases associated with Acidovorax or related bacteria.
Animal Health Component
0%
Research Effort Categories
Basic
100%
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
To identify and characterize new biological agents, microbial community structure and function, naturally suppressive soils, cultural practices, and organic amendments that provide management of diseases caused by soilborne plant pathogens.
To understand how microbial populations and microbial gene expression are regulated by the biological (plants and microbes) and physical environment and how they influence disease.
Provide outreach, education, extension and technology transfer to our clients and stakeholders- growers, biocontrol industry, graduate and undergraduate students, K-12 students and other scientists.
Project Methods
The project's objectives are:1) Develop mutants of phytopathogenic Acidovorax species lacking the S-layer and assess their virulence.2) Examine A. avenuae subsp. citrulli for nanopod production in plant tissue.3) Create mutants of A. avenuae subsp. citrulli lacking selected OMV-associated proteins and assess their virulence.4) Determine expression and location in plant issues of OMV-associated proteins produced by A. avenuae subsp. citrulli.The proposed studies will test two hypotheses:1) Nanopods and S-layer mediate intercellular associations that are key to Acidovorax virulence (addressed in Objectives 1 and 2).2) OMV Deployed within Acidovorax nanopods harbor protein virulence factors that are translocated to plant cells (addressed in Objectives 3 and 4).We will use molecular genetics techniques to develop mutants of phytopathogenic Acidovorax species lacking key genes and assess their ability to cause disease with watermelons. Virulence will be tested by inoculating fruit of watermelon plants (Citrullus lanatus) with mutant and non-mutants cells. When the disease is observed, microscopy will be used to visualize interactions of bacterial cells with those of the host plant. Results will be evaluated across scales ranging from whole plants to biomolecules. At the whole plant level, disease is assessed by decomposition of tissues. At the cellular level, bacteria-plant interactions will be evaluated by using light microscopy and electron microscopy. At the molecular scale, results are assessed by measuring changes in production of targeted proteins. By using controlled experiments, the results can be interpreted collectively. Thus, particular proteins can be linked to physical associations between plant cells and bacteria, which ultimately result in plant disease.The efforts to cause a change of knowledge will largely follow the outputs, namely publications in research journals, presentations at scientific conferences, presentations at annual meetings of the Regional Multistate, and information dissemination via websites and social media. Research papers will be evaluted for impact on academic audiences by metrics available on journal websites (citations, views, downloads). Impacts of oral presentations will be evaluated by interactions with audiences during and after the presentations.