Figure 3.  Gram-negative phytopathogenic bacteria use four major pathways to secrete effectors (type I and II) to the intercellular spaces, or directly translocate effectors (type III and IV) into the plant cell. The effectors are pathogen-produced proteins that alter the plant cell or its environment to cause disease or to trigger defense. Specific examples of effectors transported by each pathway are indicated. (Modified from Plant Disease 87:1272, fig 1) BACK