Modulation of host defense responses by Agrobacterium tumefaciens Type VI secretion system

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Bacteria frequently cause disease in plants or animals by using secretion systems to deliver protein or DNA factors that manipulate normal host cell functions and/or subvert host defenses. The soil bacterium Agrobacterium tumefaciens transports both protein and DNA into a variety of plants, resulting in tumors or "plant cancer" on infected plants. The investigators recently discovered that Agrobacteria lacking one such secretion system, the Type VI Secretion System (T6SS), are compromised in their ability to cause tumors compared to normal bacteria. The goal of this project is to determine how the factors delivered through the Agrobacterium T6SS alter or dampen the host plants? defenses. The investigators will measure the amount of specific defense compounds produced by the plant, and will monitor the extent to which the plants turn on defense-related genes in response to the normal or the T6SS-deficient bacteria. The results will reveal new information about how plants protect themselves from diseases such as plant cancer. Because similar T6SS have recently been found in a wide variety of other bacteria, including several that cause serious diseases in humans, the findings may well have relevance to these other infectious agents as well. In addition to its role in causing plant disease, Agrobacterium is widely used to introduce new genes into plants, but its utility is limited by the fact that some plants, including many economically important grain crops, are poor hosts. This project will yield new insights into the factors that make some plant species better able to resist Agrobacteria. The project fully integrates research and education, in that the experiments will be performed primarily by undergraduate students, thereby providing them with the opportunity to take a leadership role in cutting-edge research.