FIG. 1.

(a) Schematic representation of the Rhizobium etli p42d repABC operon. Gray arrows represent genes encoding proteins involved in plasmid segregation and in the negative regulation of the operon. The white arrow shows the position of the gene encoding RepC, the initiator protein. The dashed arrow indicates the position of the gene encoding the small antisense RNA (ctRNA). Squares mark the positions of the promoters: P1, the operon promoter, and P2, the ctRNA gene promoter. The oval shows the position of parS. Brackets enclose two regions involved in plasmid incompatibility. (b) ctRNA folding prediction obtained with the Mfold software (33).