Defining the requirements for the conjugative transfer of Rhizobium leguminosarum plasmid pRleVF39b

• Published in: Microbiology (Society for General Microbiology) Vol. 166; no. 3; pp. 318 - 331
• Main Authors: Wathugala, N Dulmini, Hemananda, Kasuni M, Yip, Cynthia B, Hynes, Michael F
• Format: Journal Article
• Language: English
• Published: England 01.03.2020
• Subjects: plasmid; Rhizobium; regulation; conjugation; horizontal gene transfer; relaxase
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/mic.0.000885

strain VF39 contains a plasmid, pRleVF39b, which encodes a distinctive type of conjugation system (rhizobial type IVa) that is relatively widespread among rhizobial genomes. The cluster of genes encoding the transfer functions lacks orthologs to genes such as , and , but contains 15 conserved genes of unknown function. We determined the importance of these genes in conjugation by constructing marked and unmarked mutations in each gene, and established that six genes, now designated , played a significant role in plasmid transfer. Like the relaxase gene, , and the genes encoding the MPF system ( genes), five of these genes, located in two divergently transcribed operons, are regulated by the Xre family repressor TrbR. The other gene, encodes a protein with similarity to histidinol phosphatases, and its role in conjugation is unclear, but mutations in are severely impaired for conjugation. TrcF does not play a role in regulation of other conjugation genes.