Signal Transduction in Agrobacterium Tumefaciens
Agrobacterium tumefaciens, a soil-borne α-proteobacterium, has the capacity to transfer DNA from a resident tumor inducing (Ti) plasmid into eukaryotic cells where the oncogenic transferred DNA (T-DNA) is integrated into the host genome and expressed. It is the only organism known to routinely engage in lateral gene transfer between Kingdoms, and the molecular basis of this transformation process has had considerable impact on studies of lateral DNA transfer and integration. In the case of Agrobacterium, virulent bacteria recognize signals produced at a host wound, phenols, monosaccharides, and low pH, as cues inducing expression of the Ti-encoded virulence (vir) genes. The vir gene products, among other functions, are necessary for the processing and transport of the T-DNA from the bacterium to the eukaryotic cell. Aindrila Mukhopadhyay and Rong Gao have employed biochemical and molecular genetic methods to develop a mechanism for the signal transduction process, Justin Maresh has revised models for signal perception, and Fang Fang is attempting to transfer the DNA transfer machinery to heterologous hosts.