Plasmid pSfr64a and the symbiotic plasmid pSfr64b of Sinorhizobium fredii GR64 control each other's conjugative transfer through quorum-sensing elements

GONZALO A. TORRES TEJERIZO; LAURA CERVANTES; DAVID ROMERO; FABIOLA MIRANDA; SUSANA BROM

PLASMID.

ACADEMIC PRESS INC ELSEVIER SCIENCE

Lugar: Amsterdam; Año: 2019 vol. 106

0147-619X

Rhizobia are nitrogen-fixing symbionts of plants. Their genomes frequently contain large plasmids, some of which areable to perform conjugative transfer. Plasmid pSfr64a from Sinorhizobium fredii GR64 is a conjugative plasmid, whosetransfer is regulated by quorum sensing genes encoded by itself (traR64a, traI64a), in the symbiotic plasmid pSfr64b(traR64b, traI64b), and in the chromosome (ngrI). Also, transfer of pSfr64b requires quorum sensing elementsencoded in this plasmid (traR64b, traI64b), in pSfr64a (traR64a), and in the chromosome (ngrI). These resultsdemonstrate that pSfr64a and the symbiotic plasmid depend on each other for conjugative transfer. Plasmid pSfr64afrom S. fredii GR64 is unable to transfer from the genomic background of Rhizobium etli CFN42. Our results show thatthe relaxase of pRet42a is able to process the oriT of pSfr64a, and viceversa, underlining their functional similarity andsuggesting that in addition to the external signals, the "cytoplasmic environment" may pose a barrier to plasmiddissemination, even if the plasmids are functional in other aspects.