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Sinorhizobium meliloti is an alpha-proteobacterium that alternates between a free-living phase in bulk soil or in the rhizosphere of plants and a symbiotic phase within the host plant cells, where the bacteria ultimately differentiate into nitrogen-fixing organelle-like cells, called bacteroids. As a step toward understanding the physiology of S. meliloti(More)
The 'two-component' transcriptional activator FixJ controls nitrogen fixation in Sinorhizobium meliloti. Phosphorylation of FixJ induces its dimerization, as evidenced by gel permeation chromatography and equilibrium sedimentation analysis. Phosphorylation-induced dimerization is an intrinsic property of the isolated receiver domain FixJN. Accordingly,(More)
Freezing provokes severe yield losses to different fall-sown annual legumes. Understanding the molecular bases of freezing tolerance is of great interest for breeding programs. Medicago truncatula Gaertn. is an annual temperate forage legume that has been chosen as a model species for agronomically and economically important legume crops. The present study(More)
Transcription of the Rhizobium meliloti fixK gene is induced in symbiotic and microaerobic growth conditions by the FixL/FixJ modulator/effector pair. Transcription of fixK is also negatively autoregulated. By 5' deletion analysis, the involvement in negative regulation of a DNA region between -514 and -450 with respect to the transcription start was(More)
FixJ is a phosphorylatable 'response regulator' controlling the transcription of the key nitrogen fixation genes nifA and fixK in Rhizobium meliloti. Sequence and genetic analyses indicated that FixJ comprises an N-terminal phosphorylatable regulatory domain, FixJN, and a C-terminal transcriptional activator domain, FixJC. We have now overexpressed and(More)
Using whole genome arrays, we systematically investigated nitrogen regulation in the plant symbiotic bacterium Sinorhizobium meliloti. The use of glutamate instead of ammonium as a nitrogen source induced nitrogen catabolic genes independently of the carbon source, including two glutamine synthetase genes, various aminoacid transporters and the glnKamtB(More)
Symbiotic nitrogen fixation is accompanied by a shift of Rhizobium nitrogen metabolism from ammonium assimilation to ammonium export, which probably involves genetic or metabolic regulation of glutamine synthetase activity. In free-living Rhizobium meliloti glutamine synthetase I (GSI) is regulated post-translationally by reversible adenylylation in(More)
Spartina species play an important ecological role on salt marshes. Spartina maritima is an Old-World species distributed along the European and North-African Atlantic coasts. This hexaploid species (2n = 6x = 60, 2C = 3,700 Mb) hybridized with different Spartina species introduced from the American coasts, which resulted in the formation of new invasive(More)
Allopolyploidy, which results from the merger and duplication of two divergent genomes, has played a major role in the evolution and diversification of flowering plants. The genomic changes that occur in resynthesized or natural neopolyploids have been extensively studied, but little is known about the effects of the reproductive mode in the initial(More)