The chromosomal T4SS gene cluster in XAC. (A) This T4SS cluster is located between regions XACSR12 and XACSR13. Genes shared with XauB and XauC are shown with a black asterisk. Two of the genes are shared only by XAC and XauB (red asterisk). (B) Interactions among T4SS proteins, based on data presented by Alegria et al. . Proteins specific to XAC are represented in yellow, and proteins shared by XAC, XauB and XauC are represented in orange. Six of the proteins colored in yellow are in XAC-specific regions. Genes XAC0095 and XAC0096, although not part of XAC-specific regions, seem to play an especially important role in pathogenicity. Under this model the protein coded for by XAC0095 interacts with HrpG, a protein that participates in the T3SS apparatus , and that causes phenotypic changes when its gene is mutated . The product of gene XAC0096, which is next to XAC0095, interacts wirth VirD4, a component of the T4SS .