Transformation by Agrobacterium tumefaciens requires multiple, sequential interactions between plant and bacterium. The transformation process is started when the bacterium senses a wounded plant that exudes the chemical acetosyringone. Normally this chemical acts as an antimicrobial agent, but Agrobacterium has evolved to use it as a signal to detect a wounded plant that can be infected. After activation of its T-DNA, Agrobacterium usurps a plant signal transduction pathway to eventually gain access to the plant’s nucleus and insert the T-DNA in the plant's genome. Details about this process are given in the boxes in Web Figure 2.5.A.

Web Figure 2.5.A  Detailed signal transduction pathway during the infection of plant cells with Agrobacterium.