IBBM   21076
INSTITUTO DE BIOTECNOLOGIA Y BIOLOGIA MOLECULAR
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Sequencing and analysis of pLPU83a, an accessory plasmid of a broad-host-range Rhizobium sp. LPU83
Autor/es:
TORRES TEJERIZO G, M F DEL PAPA, W DRAGHI, M LOZANO, M Á GIUSTI, C MARTINI, E SALAS, I SALTO, D WIBBERG, R SZCZEPANOWSKI , S WEIDNER , A SCHLÜTER , A PÜHLER, A LAGARES, Y M PISTORIO.
Lugar:
San Carlos de Bariloche
Reunión:
Conferencia; International Plasmid Biology Conference; 2010
Resumen:
Bacteria belonging to the genera Rhizobium,
Sinorhizobium, Azorhizobium, and
Mesorhizobium grow in the soil in free-living conditions, and in symbiosis
associated with the root of legumes as nitrogen-fixing organisms. A general
feature of rhizobia is the presence of large amount of plasmid that DNA in
their genomes. Rhizobia could borne plasmids whose role is not currently understood,
referred as accessory plasmids. Conjugal transfer of rhizobial plasmids has
been well documented since decades ago. In our laboratory we have characterized
acid-tolerant isolates of rhizobia that have an extended host range for
nodulating alfalfa, the common bean, and Leucena leucocephala (1). Such isolates
have been shown to be closely related to the previously described strain R. sp.
Or191, isolated from an acid soil in Oregon, USA (2). The
genetic structure of the Or-like strains is particularly relevant since they
have a chromosome related to the bean-, pea-, and clover-nodulating rhizobia;
and they contain plasmid-encoded symbiotic genes related to those present in
the Medicago symbionts (3). We were interested in the characterization of the
plasmid gene pool present in Medicago-nodulating rhizobia in order to ascertain
the plasmid-related evolutionary relationships within this group of rhizobia.
We have previously analyzed the conjugation and symbiotic characteristics of
the plasmids of R. sp. LPU83. To make a deeper characterization a sequencing
approach was carried out and the final assembly results in a 148 kbp contig for
plasmid pLPU83a. 157 predicted coding sequences were annotated and categorized
by functional class by the use of Clusters of Orthologous Groups (COG). With
this classification, genes for DNA replication, recombination and repair,
Intracellular trafficking and secretion and Cell wall/membrane/envelop
biogenesis, were well represented. A
detailed analysis revels that a cluster of genes involved in the Mpf/Dtr
similar to the one presented in pRL8 of Rhizobium leguminosarum bv. viciae is
presented in pLPU83a, where the absence of traI is remarkable. Anyway, an
ortholog of traI is presented faraway of this gene cluster. The
characterization of the Or-like plasmids will be valuable in the elucidation of
mechanisms involved in the evolution and diversification of the alfalfa- and
bean-nodulating rhizobia.