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Lotus japonicus and Medicago truncatula model legumes, which form determined and indeterminate nodules, respectively, provide a convenient system to study plant-Rhizobium interaction and to establish differences between the two types of nodules under salt stress conditions. We examined the effects of 25 and 50mM NaCl doses on growth and nitrogen fixation(More)
Trehalose (alpha-D-glucopyranosyl-1,1-alpha-D-glucopyranoside), a non-reducing disaccharide, has been found in a wide variety of organisms playing an important role as an abiotic stress protectant. Plants may come into contact with trehalose from exogenous sources, such as in plant-rhizobia symbiosis in which the rhizobia have the capacity to produce(More)
The effect of NaCl stress (50 mM) and validamycin A treatment (30 mM) on growth and nitrogen fixation of Lotus japonicus was investigated in plants cultured under symbiotic and hydroponics conditions for teen weeks (flowering stage). Validamycin A was used as a potent trehalase inhibitor, and was able to produce a five-fold increase in the level of(More)
A simple approach was used to identify Rhizobium meliloti DNA regions with the ability to convert a nontransmissible vector into a mobilizable plasmid, i.e., to contain origins of conjugative transfer (oriT, mob). RecA-defective R. meliloti merodiploid populations, where each individual contained a hybrid cosmid from an R. meliloti GR4 gene library, were(More)
We have examined nutritional factors influencing conjugal transfer of the two nonsymbiotic large plasmids, pRmeGR4a and pRmeGR4b, of Rhizobium meliloti GR4. To monitor transfer, each plasmid was tagged with a different antibiotic resistance marker. Transfer of plasmid pRmeGR4b was dependent upon the presence of plasmid pRmeGR4a on the same donor cell.(More)
An approach originally designed to identify functional origins of conjugative transfer (oriT or mob) in a bacterial genome (J. A. Herrera-Cervera, J. M. Sanjuán-Pinilla, J. Olivares, and J. Sanjuán, J. Bacteriol. 180:4583-4590, 1998) was modified to improve its reliability and prevent selection of undesired false mob clones. By following this modified(More)
An analysis of the conjugative transfer of pRetCFN42d, the symbiotic plasmid (pSym) of Rhizobium etli, has revealed a novel gene, rctA, as an essential element of a regulatory system for silencing the conjugative transfer of R. etli pSym by repressing the transcription of conjugal transfer genes in standard laboratory media. The rctA gene product lacks(More)
The purification and characterization of trehalase from common bean nodules as well as the role of this enzyme on growth, nodulation nitrogen fixation by examining the effects of the trehalase inhibitor validamycin A, was studied. Validamycin A did not affect plant and nodule mass, neither root trehalase and nitrogenase activity; however this treatment(More)
Genetic and biochemical characterization of TraA, the relaxase of symbiotic plasmid pRetCFN42d from Rhizobium etli, is described. After purifying the relaxase domain (N265TraA), we demonstrated nic binding and cleavage activity in vitro and thus characterized for the first time the nick site (nic) of a plasmid in the family Rhizobiaceae. We studied the(More)
This study compared growth, nodulation, nitrogen fixation, and nodular enzyme activities in response to salinity in some common bean-rhizobia symbiotic combinations. Seeds of Paulista and Efequince, two varieties of the common bean (Phaseolus vulgaris) were germinated and seedlings were transferred to pots containing vermiculite inoculated with the(More)