Pathogenesis of Agrobacterium

Pathogenesis of Crown Gall
Peter Sforza, Dan Tillman, George Lacy, Mary Ann Hansen, and John Jelesko

3-D Animations:
The Natural Pathogenesis of Agrobacterium (21 MB avi) (19 MB mov)

The first step of this project (PPWS 5114 class project) was to research and design 3-D models that could be used as the 'raw materials' for a presentation on the pathogenesis of Agrobacterium tumefaciens and the Ti-plasmid.

Mary Ann Hansen and John Jelesko have provided many helpful comments for the recent work on the Agrobacterium animations. Current works in progress include, the natural pathogenesis of Agrobacterium (21 MB avi) (19 MB mov). Constructive comments are welcomed. We are working on a narrative and video to accompany the animations.

A discussion of the pathogen(s) will describe the relationship
between the bacterium, the plasmid, and the host.
Is Agrobacterium tumefaciens
the pathogen? Or are the plasmid and bacterium merely
vectors of the pathogenic T-DNA?
Semantics aside, it is a fascinating interaction.

A 3-D model of Gram-negative
and Gram-positive cell walls.

Click the image to enlarge.

Flagellar movement of bacteria.
A wounded plant cell will begin
to synthesize lignin. Certain
lignin precursors are chemotactically
sensed by the pathogen. Flagellar
movement is counterclockwise up
the gradient and cells have been
reported to move as fast as
60 um/second.

A. tumefaciens exhibits polar attachment to the plant cell.
The production of cellulose fibrils serve to anchor the bacteria to the plant
as well as trap other bacteria. Once the concentration of lignin precursors
reaches approximately 10^-5 M, the virulence genes of the Ti plasmid are induced
and the T-DNA is processed.

pla_cell.jpg (23028 bytes)
Plant cell with nucleus and endoplasmic reticulum

pla_nucleus.jpg (34458 bytes)
Plant cell nucleus with nuclear pores, the entry site for T-DNA

The actual mechanism of T-DNA
transfer is difficult to animate. The model at left
lacks the double stranded intermediate of the T-DNA,
but shows in an approximate manner how the T-DNA
moves into the plant cell and is passed
through the nuclear pores.

Once all of these raw materials are developed, they will be arranged in a presentation to tell the story of the pathogenesis of Agrobacterium tumefaciens and the Ti-plasmid.