Caracterización molecular de las funciones de replicación y movilización en un plásmido críptico de Sinorhizobium meliloti

GIUSTI, M.A.; PISTORIO, M.; LOZANO, M.J.; TORRES TEJERIZO, G.A.; DRAGHI, W.O.; LAGARES, A.

Cordoba, Argentina

Congreso; XXIII Reunión Latinoamericana de Rhizobiología; 2007

Asociación Latinoamericana de Rhizobiología

A general characteristic of several species of (sino)rhizobia is the presence of significant amounts of extrachromosomal DNA. The conjugal transfer of symbiotic and cryptic plasmids has been demonstrated in several rhizobia. In our laboratory we have previously identified a S. meliloti conjugal binary system cons¬tituted by a 30 kb mobilizable plasmid (pSmeLPU88b) and a 139 kb helper plasmid (pSmeLPU88b). We have now identified the replication and mobilization regions of plasmid pSmeLPU88b. Two ORFs coding for replication initiation proteins were identified, one of them belonging to the repC type A class, and the other to the repABC family. Both of them were able to support replication of suicide plasmids in S. meliloti. With a similar strategy we have identified elements of the Dtr region of plasmid pSmeLPU88b, including a puta¬tive relaxase which does not belong to any of the previously described groups of similar proteins. We are currently analyzing the presence of related rep and Dtr sequences in a consolidated collection of S. melilo¬ti plasmids, toward the characterization of basic structural modules that play central roles in the evolutio¬nary mechanisms of the sinorhizobial mobilome.