Mutations in an antisense RNA, involved in the replication control of a repABC plasmid, that disrupt plasmid incompatibility and mediate plasmid speciation.
The maintenance of large plasmid in a wide variety of alpha-proteobacteria depends on the repABC replication/segregation unit. The intergenic repB-repC region of these plasmids encodes a countertranscribed RNA (ctRNA) that modulates the transcription/translation rate of RepC, the initiator protein. The ctRNA acts as a strong incompatibility factor when expressed in trans. We followed a site directed mutagenesis approach to map those sequences of the ctRNA that are required for plasmid incompatibility and for plasmid replication control. We found that the first three nucleotides of the 5'-end of the ctRNA are essential for interactions with its target RNA. We also found that stretches of 4-5 nucleotides of non-complementarity within the first 10 nucleotides of the left arm of the ctRNA and the target RNA are sufficient to avoid plasmid incompatibility. Additionally, miniplasmid derivatives expressing ctRNAs with mutations in the 5' end or small deletions in the ctRNA are capable of controlling their own replication and coexisting with the parental plasmid. We suggest that a mechanism that could have a crucial role in the speciation process of repABC plasmids is to accumulate enough changes in this small region of the ctRNA gene to disrupt heteroduplex formation between the target RNA of one plasmid and the ctRNA of the other. Plasmids carrying these changes will not have defects in their maintenance.
['Rivera-Urbalejo|América|A|', 'Pérez-Oseguera|Ángeles|Á|', 'Carreón-Rodríguez|Ofelia E|OE|', 'Cevallos|Miguel A|MA|']
D001483:Base Sequence D004261:DNA Replication D015964:Gene Expression Regulation, Bacterial D008969:Molecular Sequence Data D009154:Mutation D009876:Operon D010957:Plasmids D014176:Protein Biosynthesis D016372:RNA, Antisense D042163:Rhizobium etli D014158:Transcription, Genetic
Replication control Alpha-proteobacteria Plasmid evolution Rhizobium