Location of nodulation and nitrogen fixation genes on a high molecular weight plasmid of R. meliloti

Bánfalvi, Zsófia; Sakanyan, Vehary; Koncz, Csaba; Kiss, Antal; Dusha, Ilona; Kondorosi, Ádám

doi:10.1007/bf00272925

Cited by 322 publications

(103 citation statements)

References 36 publications

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“…The same reasoning with the distal SmaI-EcoRI fragment suggests the existence of nif genes corresponding to K. pneumoniae nifY(Puihler and Klipp, 1981) or K. pneumoniae, nifE or both. This differs slightly from previous observations made in other Rhizobium species where no hybridization with plasmid pCM1 was found (Prakash et al, 1981) and where no homology with K. pneumoniae nifK was detected (Banfalvi et al, 1981;Hennecke, 1981;Ruvkun and Ausubel, 1981). In R. meliloti and R. japonicum, homology was limited to nifH and nifD and the size of the homologous fragment was -2.6 kb.…”

Section: Discussioncontrasting

confidence: 98%

Genetic analysis of nitrogen fixation in a tropical fast-growing Rhizobium

et al. 1982

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The Rhizobium strain ORS571, which is associated with the tropical legume Sesbania rostrata, has the property of growing in the free‐living state at the expense of ammonia or N2 as sole nitrogen source. Five mutants, isolated as unable to form colonies on plates under conditions of nitrogen fixation, were studied. All of them, which appear as Fix‐ in planta, are nif mutants. With mutant 5740, nitrogenase activity of the crude extract was restored by addition of pure Mo‐Fe protein of Klebsiella pneumoniae. A 13‐kb BamHI DNA fragment from the wild‐type strain, which hybridized with a probe carrying the nifHDK genes of K. pneumoniae, was cloned in vector pRK290 to yield plasmid pRS1. The extent of homology between the probe and the BamHI fragment was estimated at 4 kb and hybridization with K. pneumoniae nifH, nifK, and possibly nifD was detected. The pRS1 plasmid was introduced into the sesbania rhizobium nif mutants. Genetic complementation was observed with strain 5740(pRS1) both in the free‐living state and in planta. It thus appears that biochemistry and genetics of nitrogen fixation in this particular Rhizobium strain can be performed with bacteria grown under non‐symbiotic conditions.

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Section: Discussioncontrasting

confidence: 98%

Genetic analysis of nitrogen fixation in a tropical fast-growing Rhizobium

et al. 1982

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“…Rhizobium meliloti interacts symbiotically with alfalfa (Medicago sativa) by forming root nodules in which the bacteria fix nitrogen. Most of the symbiotic genes of R. meliloti are located on very large plasmids (megaplasmids, Banfalvi et al, 1981;Rosenberg et al, 1981). The genes coding for early nodulation functions which are common to a wide range of plant hosts ('common' nod genes) are clustered on a 4-kb region of the megaplasmid Schmidt et al, 1984).…”

Section: Introductionmentioning

confidence: 99%

Expression of the nodulation gene nod C of Rhizobium meliloti in Escherichia coli : role of the nod C gene product in nodulation

et al. 1985

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The nod C gene of Rhizobium meliloti encodes a protein of mol. wt. 44 000 which is highly conserved in at least three Rhizobium species. In order to overproduce this protein, a gene fusion of λcI repressor sequences to a large fragment of nod C was constructed. The fusion was placed under control of the tac promoter on plasmid pEA305 to yield pJS1035. IPTG‐induced Escherichia coli cells harbouring pJS1035 accumulated the cI‐nod C hybrid protein up to 19% of total cellular protein. The synthesis of the hybrid protein drastically inhibits the growth rate of the bacterium. The fusion protein was purified by gel and hydroxyapatite chromatography in the presence of SDS. Antibodies raised against the purified fusion protein precipitated the mol. wt. 44 000 nod C proteins of R. meliloti and of the broad‐host range Rhizobium strain NGR234, which were both expressed in E. coli minicells. The hybrid protein is associated with the outer membrane of E. coli cells, and the cI‐nod C fusion protein appears to be an integral membrane protein. Nodulation of alfalfa by R. meliloti and of clover by R. trifolii was markedly inhibited (˜50%) by the addition of antibodies against the hybrid protein to plant growth medium and inoculum.

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“…Among the genes found to be directly involved in symbiotic nitrogen fixation in fast-growing rhizobia (fix, nif, nod and hsn) Banfalvi et al, 1981;Rosenberg et al, 1981;Hooykaas et al, 1981), the common and host-specific nodulation genes are those which play an active part in the earliest stages of the infection process .…”

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confidence: 99%

Host-specific regulation of nodulation genes in Rhizobium is mediated by a plant-signal, interacting with the nodD gene product

et al. 1987

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We have identified a nodD gene from the wide host‐range Rhizobium strain MPIK3030 (termed nodD1) which is essential for nodulation on Macroptilium atropurpureum (siratro). Experiments with nodA–lacZ gene fusions demonstrate that the MPIK3030 nodD1 regulates expression of the nodABC genes. Additionally, we used nodC–lacZ fusions of Rhizobium meliloti to show that the MPIK3030 nodD1 gene induces expression of these fusions by interacting with plant factors from siratro and from the non‐host Medicago sativa (alfalfa). The R. meliloti nodD genes, however, only interact with alfalfa exudate. In line with these results, no complementation of MPIK3030 nodD1 mutants could be obtained on siratro with the R. meliloti nodD genes, while the MPIK3030 nodD1 can complement nodD mutants of R. meliloti on alfalfa. Furthermore, R. meliloti transconjugants harbouring the MPIK3030 nodD1 efficiently nodulate the illegitimate host siratro. When compared with other nodD sequences, the amino acid sequence of the MPIK3030 nodD1 shows a conserved aminoterminus, whereas the carboxy‐terminus of the putative gene product diverges considerably. Studies on a chimeric MPIK3030/R. meliloti nodD gene indicates that the carboxy‐terminal region is responsible for the interaction with plant factor(s) and may have evolved in different rhizobia specifically to interact with plant–host factors.

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Location of nodulation and nitrogen fixation genes on a high molecular weight plasmid of R. meliloti

Cited by 322 publications

References 36 publications

Genetic analysis of nitrogen fixation in a tropical fast-growing Rhizobium

Genetic analysis of nitrogen fixation in a tropical fast-growing Rhizobium

Expression of the nodulation gene nod C of Rhizobium meliloti in Escherichia coli : role of the nod C gene product in nodulation

Host-specific regulation of nodulation genes in Rhizobium is mediated by a plant-signal, interacting with the nodD gene product

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