Professor of Crop Sciences
and of Microbiology
My lab is interested in the biology and the molecular biology of the plant pathogen, Agrobacterium tumefaciens. This organism causes tumors, called crown galls, on susceptible plants. Tumor induction results from the transfer of a small piece of DNA, called T-DNA, from the bacterium to the plant cell during infection. The T-DNA becomes integrated into plant cell nuclear DNA and expression of genes on this segment causes the normal plant cell to differentiate into a tumor cell. Expression of additional T-DNA genes causes the plant tumor cells to produce and secrete novel small carbon compounds called opines. In turn, Agrobacterium cells can utilize opines as sole carbon and energy sources. In the bacterium, the T-DNA and the genes for opine catabolism reside on a large, extrachromosomal virulence element called the Ti plasmid. This plasmid itself is transmissible from the bacterium to recipient bacteria by a mating mechanism called conjugation. To find out more about conjugation, opine catabolism, and plant signaling click on Research Areas in the left frame.