IBBM   21076
INSTITUTO DE BIOTECNOLOGIA Y BIOLOGIA MOLECULAR
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Characterization of the oriT region from a smal cryptic plasmid from Sinorhizobium meliloti LPU88.
Autor/es:
GIUSTI MA, M PISTORIO ,M LOZANO , G A. TORRES TEJERIZO, M E SALAS 1, M C MARTINI 1, M F DEL PAPA1, DL PÉREZ MENDOZA2, J SANJUAN AND A LAGARES
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.