title: Transposon mediation allows a symbiotic plasmid of Rhizobium leguminosarum bv. trifolii to become a symbiosis island in Agrobacterium and Rhizobium.
abstract: The symbiotic plasmid (pSym) of Rhizobium leguminosarum bv. trifolii 4S5, which carries Tn5-mob, was successfully transferred into Agrobacterium tumefaciens A136 by using a conjugation method. The resulting transconjugants induced the development of ineffective nitrogen-fixing nodules on the roots of white clover seedlings. Depending on the manner in which the pSym was retained, the transconjugants were divided into two groups of strains, Afp and Afcs. pSym was retained as a plasmid in the Afp strains but was integrated into the int gene encoding a phage-related integrase on the linear chromosome of A. tumefaciens A136 in strain Afcs1 (one of the Afcs strains) to form a symbiosis island. Conjugation was performed between strain Afcs1 and R. leguminosarum bv. trifolii H1 (a pSym-cured derivative of wild-type strain 4S), and the Rhizobium H1tr strains were screened as transconjugants. Eighteen of the H1tr strains induced effective nitrogen-fixing nodules on the roots of the host plants. pSym was transferred into all of the transconjugants, except for strain H1tr1, at the same size as pSym of strain 4S5. In strain H1tr1, pSym was integrated into the chromosome as a symbiosis island. These data suggest that pSym can exist among Rhizobium and Agrobacterium strains both as a plasmid and as a symbiosis island with transposon mediation.
authors.affiliation: Graduate School of Science and Engineering, Kagoshima University, Kagoshima, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Nakatsukasa
authors.forename: Toshiki
authors.initials: T
authors.lastname: Uchiumi
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Kucho
authors.forename: Akihiro
authors.initials: A
authors.lastname: Suzuki
authors.forename: Shiro
authors.initials: S
authors.lastname: Higashi
authors.forename: Mikiko
authors.initials: M
authors.lastname: Abe
mesh_terms: D001483:Base Sequence; D002876:Chromosomes, Bacterial; D003227:Conjugation, Genetic; D015342:DNA Probes; D004251:DNA Transposable Elements; D016521:Electrophoresis, Gel, Pulsed-Field; D044404:Genomic Islands; D015698:Genomic Library; D008969:Molecular Sequence Data; D009586:Nitrogen Fixation; D020161:Physical Chromosome Mapping; D010957:Plasmids; D012231:Rhizobium / Q000235:genetics*; D016961:Rhizobium leguminosarum / Q000235:genetics*; D053204:Root Nodules, Plant / Q000382:microbiology; D029921:Trifolium / Q000382:microbiology
chemical_list: D015342:DNA Probes; D004251:DNA Transposable Elements