Agrobacterium tumefaciens is found as free-living bacteria in the soils of most temperate and tropical climates. Certain strains of the bacterium can infect a wide variety of plants and cause them to develop tumors. This occurs as a result of the activation of a variety of molecular processes in the bacterium that provide it with the capacity to induce plant tumors. Interestingly, some plant species do not appear to respond to the bacteria by forming tumors and in plants that do form tumors, certain tissue types seem significantly more susceptible. The investigators are determining how the bacteria recognize that they are on a plant - or more precisely in particular plant tissues. After coming into close proximity with plant tissues the bacterium recognizes different chemicals produced by the plant, including phenolic derivatives and certain sugars. Both types of molecules are required to induce the synthesis of bacterial products required to cause tumors to develop. Intriguingly, the distribution of these molecules is not uniform around the plant. The investigators have designed a series of experiments that will allow them to map the distribution of the signals within the plant (thereby determining the 'signal landscape'). Through these studies they will then be able to determine whether regions of the plant that make tumors in response to the bacteria are the only regions of the plant that make the appropriate signals. This, for example, could lead to the identification of tissues that don't make tumors even when the bacteria are 'artificially activated' and thereby lead to an understanding of how these tissues 'defend' themselves against the tumor causing actions of the bacterium.

A team of scientists whose areas of expertise comprise chemistry, biochemistry, plant pathology, molecular biology, and microbiology will direct the project. This provides a strong interdisciplinary training environment for postdoctoral, graduate and undergraduate students. The planned experiments will provide projects for three to six undergraduate students who work in our laboratories. Students will get 'hands on' experience in molecular biological, biochemical, and cell culture techniques and the opportunity to present their work to their peers. Moreover, both PIs have been extensively involved in alternative approaches to science education and can incorporate many aspects of the proposed work into these projects.

National Science Foundation (NSF)
Division of Integrative Organismal Systems (IOS)
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Michael L. Mishkind
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University of Pennsylvania
United States
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