Nitrogenase reductase: A functional multigene family in
            <i>Rhizobium phaseoli</i>

Quinto, Carmen; Vega, Humberto de la; Flores, Margarita Avilés; Leemans, J.; Cevallos, Miguel A.; Pardo, Marco Aurelio; Azpiroz, Ricardo; Girard, M.; Calva, Edmundo; Palacios, Rafael

doi:10.1073/pnas.82.4.1170

Cited by 134 publications

(93 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Duplication of genes involved in symbiotic nitrogen fixation is not uncommon in rhizobia (26,36,39), and even the fixK gene itself is reiterated in the symbiotic plasmid of R. meliloti (41). In all of these cases, the gene repeats were easily identifiable by hybridization.…”

Section: T V P L P M S R Q D I a D Y L G L T I E T V S R T F T K L mentioning

confidence: 83%

Characterization of a fixLJ-regulated Bradyrhizobium japonicum gene sharing similarity with the Escherichia coli fnr and Rhizobium meliloti fixK genes

1992

View full text Add to dashboard Cite

We describe the cloning, sequencing, regulation, and mutational analysis of a Bradyrhizobium japonicum fixK-like gene whose product belongs to the family of Fnr-Crp-related regulatory proteins. The predicted 237-amino-acid FixK protein was found to share between 28 and 38% sequence identity with the Escherichia coli Fnr protein, other bacterial Fnr-like proteins (FnrN, Anr, and HlyX), and two rhizobial FixK proteins.

show abstract

Section: T V P L P M S R Q D I a D Y L G L T I E T V S R T F T K L mentioning

confidence: 83%

Characterization of a fixLJ-regulated Bradyrhizobium japonicum gene sharing similarity with the Escherichia coli fnr and Rhizobium meliloti fixK genes

1992

View full text Add to dashboard Cite

show abstract

“…An R. phaseoli CFN42 genomic library with the bacteriophage X1059 as vector was previously constructed (33). In this library, the 17-kb BamHI fragment that contains red and gamma genes was substituted by BamHI genomic fragments.…”

Section: Resultsmentioning

confidence: 99%

“…The R. phaseoli CFN42 genomic library in X1059 was previously constructed (33) and propagated in E. coli Q359 as described by Karn et al (19).…”

Section: Methodsmentioning

confidence: 99%

Molecular cloning and characterization of the recA gene of Rhizobium phaseoli and construction of recA mutants

et al. 1991

View full text Add to dashboard Cite

The Rhizobium phaseoli recA gene has been cloned by interspecific complementation of the Fec phenotype of bacteriophage lambda. The cloned gene restored the recombination proficiency and conferred resistance to DNA-damaging agents (methyl methanesulfonate and nitrofurantoin) to an Escherichia coli recA mutant. The direction of transcription and the localization of the recA gene were determined by mutagenesis with phage MudIIPR13 and heterologous hybridization with an E. coli recA probe. An R. phaseoli recA::Spc' mutation was introduced in two R. phaseoli strains by homogenotization. The R. phaseoli recA mutants were more sensitive to DNA-damaging agents and exhibited a 100-fold reduction in recombination frequency as compared with their parental strains. A deletion of the symbiotic plasmid abolishing nodulation was found at high frequency (10-2) in R. phaseoli CFN42. This event was recA dependent. In R. phaseoli CFN285, two events of symbiotic instability were found at high frequency (l0-3): one was a deletion in the symbiotic plasmid, and the other was the loss of whole symbiotic plasmid. In the CFN285 recA::Spcr mutant, only the loss of the symbiotic plasmid was observed.The product of the Escherichia coli recA gene is involved in several functions of DNA metabolism. The RecA protein is required for processes of homologous recombination, DNA repair, and induction of prophages, bacteriocins, and SOS genes, as well as for the coordination of cell division events (6,41,45).The purified RecA protein is a DNA-dependent ATPase that in vitro promotes the invasion of duplex DNA by homologous single-stranded DNA, and its activated form (apparently by binding to single-stranded DNA) accelerates the cleavage of the LexA repressor, causing the induction of SOS genes. The activated RecA protein is also responsible for the proteolysis of the lambda repressor, promoting the lytic growth of the prophage (6,41,45).The important functions played by the recA gene in cell metabolism suggest that a recA gene may be conserved in many species. In fact, interspecific complementation of E. coli recA mutants has been used to obtain recA genes from at least 16 bacterial species, including five members of the Enterobacteriaceae family (9, 21), two members of the Rhizobiaceae family (2, 10), and other species (1,15,16,23,24,31,35).A high degree of DNA reiteration is a general characteristic of the Rhizobiaceae genome (11,27). This feature has been reported only for a few other bacterial species, such as Halobacterium and Streptomyces species (38, 39). Moreover, a high frequency of rearrangements has been found to be associated with the presence of repeated DNA (12, 38). Genomic instability and rearrangements that affect nodulation or nitrogen fixation abilities have been observed in several Rhizobium species (25,27,37,42).In this report we describe the isolation of the Rhizobium phaseoli recA gene. The cloned gene complements an E. coli recA mutant for recombination and DNA repair activities. Stable R. phaseoli recA mutants were obtained ...

show abstract

“…Plasmid profiles were obtained by the in-gel lysis method of Eckhardt (8), blotted onto nitrocellulose, and hybridized similarly. The internal nipH fragment used as a probe was a 0.27-kb Sall fragment from the R. phaseoli nifH gene (from codon 29 to codon 120) located in nif region a (34). The extent of the R. phaseoli ni,fD-and nifK-specific probes is shown in Fig.…”

Section: Methodsmentioning

confidence: 99%

Amplification and deletion of a nod-nif region in the symbiotic plasmid of Rhizobium phaseoli

et al. 1991

View full text Add to dashboard Cite

One remarkable characteristic of the genomes of some Rhizobium species is the frequent occurrence of rearrangements. In some instances these rearrangements alter the symbiotic properties of the strains. However, no detailed molecular mechanisms have been proposed for the generation of these rearrangements. To understand the mechanisms involved in the formation of rearrangements in the genome of Rhizobium phaseoli, we have designed a system which allows the positive selection for amplification and deletion events. We have applied this system to investigate the stability of the symbiotic plasmid of R. phaseoli. High-frequency amplification events were detected which increase the copy number of a 120-kb region carrying nodulation and nitrogen fixation genes two to eight times. Deletion events that affect the same region were also found, albeit at a lower frequency. Both kinds of rearrangements are generated by recombination between reiterated nitrogenase (nifHDK) operons flanking the 120-kb region.Rhizobium spp. are gram-negative soil bacteria studied primarily for their ability to establish nitrogen-fixing symbioses with leguminous plants. Intensive genetic analysis during the past decade has led to the identification of genes essential for the nodulation (nod genes) and nitrogen fixation (nif and fix genes) processes. In all the fast-growing Rhizobium species, these genes are carried on large plasmids, the so-called Sym plasmids or pSym (20,24).One interesting characteristic of the Rhizobium genome is the presence of a large number of reiterated DNA sequences. For Rhizobium phaseoli, the symbiont of the common bean (Phaseolus vulgaris L.), we have estimated the presence of about 700 reiterated elements, belonging to 200 different families (9). This high degree of reiteration is not restricted to R. phaseoli; other members of the Rhizobiaceae family, including the closely related bacteria Agrobacterium tumefaciens, possess a large amount of reiterated DNA (9, 24). For other organisms, it has been shown that recombination between pairs of repeated elements may lead to different kinds of genomic rearrangements, including additions, amplifications, deletions, and inversions (2, 31).Frequent genomic rearrangements (in the range of 10-2 to 10-3) have been commonly observed in different Rhizobium species, including Bradyrhizobium japonicum, Rhizobium trifolii, and R. phaseoli. These rearrangements, which are frequently deletions, may affect the symbiotic properties of the strain, either for nodulation or for nitrogen fixation (4,7,10,14,18,39,44). Unfortunately, the mechanisms involved in the generation of genetic instability in these species have been poorly analyzed.In order to understand the mechanisms involved in the genetic instability of R. phaseoli, we have developed an experimental approach for the general selection of genomic rearrangements. This system allows the positive selection of different kinds of rearrangements, including amplifications, deletions, insertions, and loss of plasmids. We have used this sys...

show abstract

Nitrogenase reductase: A functional multigene family in Rhizobium phaseoli

Abstract: The complete coding sequence of the nitro-

Cited by 134 publications

References 38 publications

Characterization of a fixLJ-regulated Bradyrhizobium japonicum gene sharing similarity with the Escherichia coli fnr and Rhizobium meliloti fixK genes

Characterization of a fixLJ-regulated Bradyrhizobium japonicum gene sharing similarity with the Escherichia coli fnr and Rhizobium meliloti fixK genes

Molecular cloning and characterization of the recA gene of Rhizobium phaseoli and construction of recA mutants

Amplification and deletion of a nod-nif region in the symbiotic plasmid of Rhizobium phaseoli

Contact Info

Product

Resources

About