Figure 11.

Proposed model of DFG‐inducible transfer of pAoF64/95. The genes involved in mannopine uptake and utilization are colored black, the tra regulon is light gray, and the plasmid replication and partitioning genes are dark gray. The genes and proteins involved in mannopine‐inducible transfer are as follows: traR/TraR, black dots on a white background; traM/TraM, diagonal stripes; mrtR/MrtR, horizontal stripes; and tmsP/TmsP, crosshatched. Agrobacterium autoinducer (AAI) is indicated by σ. All other genes are in white. Promoters are indicated by “P” and transcriptional direction is indicated by the arrows. Under noninducing conditions TraM binds to TraR preventing activation of the three promoters of the tra regulon while MrtR represses transcription of the mannopine catabolism and uptake operons including tmsP. When DFG is present, repression by MrtR is relieved and tmsP is transcribed. TmsP binds to TraM and sequesters the antiactivator thereby freeing TraR, which, as long as the population has reached its critical threshold and enough AAI is available, can form active dimers and activate transcription of the tra regulon