RUI: Role of VirC1 and VirC2 in Regulation of Substrate Delivery by the VirB/D4 Secretion Apparatus of Agrobacterium Tumefaciens

Williams College, Williamstown MA

Investigators

Abstract

The soil bacterium Agrobacterium tumefaciens transports both proteins and DNA into a host plant cell, resulting in crown gall tumors ('plant cancer') at the infection site. The transport machinery, comprised of multiple VirB proteins and VirD4 working as a complex in the bacterial membrane to promote export of the DNA and proteins, is the prototype for several similar systems required for other medically significant bacteria to cause disease in their mammalian hosts. The goal of the project is to characterize two proteins, VirC1 and VirC2, that appear to enhance the efficiency of DNA delivery via this transport apparatus. This research will test the hypothesis that VirC1 and VirC2 interact to tether the source of the transferred DNA to specific sites on the bacterial cell membrane, thereby promoting DNA interactions with the VirB/VirD4 secretion machinery. Biochemical and microscopic approaches will be used to determine if VirC1 associates with components of the transport complex. The influence of host cell contact on these interactions will be investigated. Biochemical and genetic approaches will be used to probe for interactions between VirC1 and VirC2. The data obtained will also reveal where VirC2 is located within the cell, and whether a specific region of the VirC1 protein is essential for VirC1's functions. The results will provide novel information about two poorly characterized virulence proteins and, more broadly, the regulation of trafficking through an important model secretion system. Agrobacterium tumefaciens is widely used to introduce new genes into plants, but its utility is limited by the fact that some plants, including many agriculturally important grains, are poor hosts. These investigations into the roles played by VirC may well have significant implications for the genetic modification of hitherto non-host species, and hence for global food productivity. The project will be used to provide undergraduates in opportunities to do research.