Disease relevance of Rhizobium

• The endonuclease function was further localized to the 5' end of this operon by demonstrating that cleavage does not occur in virD mutant strains of Agrobacterium and that the 5' end of the virD operon is sufficient to direct cleavage in E. coli [1].
• Klebsiella pneumoniae nifA product activates the Rhizobium meliloti nitrogenase promoter [2].
• Hypoxia is known to induce a tyrosine kinase cascade that results in the activation of nitrogen-fixation genes in Rhizobium meliloti, and activation of tyrosine kinases is critical in signalling triggered by growth factors and ultraviolet light [3].
• We have isolated and characterized a consortium of two microorganisms, Arthrobacter ilicis and Agrobacterium radiobacter, that mineralized recalcitrant ethylene glycol dinitrate [4].
• We discovered a natural system that may serve as a model for investigating this problem: the repressor of the 16-3 phage of Rhizobium meliloti (helix-turn-helix class protein) possesses inherent ability to accommodate to various DNA twistings [5].

High impact information on Rhizobium

• Rhizobium common and host-specific nodulation genes are essential for the production of these compounds [6].
• We report the discovery of two genes from Rhizobium meliloti, fixL and fixJ, which are positive regulators of symbiotic expression of diverse nitrogen fixation (nif and fix) genes. nif gene regulation is shown to consist of a cascade: the fixLJ genes activate nifA, which in turn activates nifHDK and fixABCX [7].
• The virD operon of Agrobacterium tumefaciens encodes a site-specific endonuclease [1].
• Agrobacterium tumefaciens and the susceptible plant cell: a novel adaptation of extracellular recognition and DNA conjugation [8].
• Cloned DNA sequences encoding yeast alcohol dehydrogenase and a bacterial neomycin phosphotransferase have been inserted into the T-DNA of Agrobacterium tumefaciens plasmid pTiT37 at the "rooty" locus [9].

Chemical compound and disease context of Rhizobium

• The A6S/2 tumor incited on tobacco by Agrobacterium tumefaciens harboring the octopine-type A6 Ti plasmid contains one insert of Ti-plasmid sequences (the T DNA) [10].
• We report here that the infection of soybean (Glycine max L.) roots with Rhizobium japonicum results in the synthesis by the plant of at least 18-20 polypeptides other than leghemoglobin during the development of root nodules [11].
• Symbiotic host-specificity of Rhizobium meliloti is determined by a sulphated and acylated glucosamine oligosaccharide signal [12].
• A plant flavone, luteolin, induces expression of Rhizobium meliloti nodulation genes [13].
• Oncogenes carried by the transferred DNA (T-DNA) of Agrobacterium Ti plasmids encode the synthesis of plant growth factors, auxin and cytokinin, and induce tumour development in plants [14].

Biological context of Rhizobium

• It has been proposed that the bacterial genes nodABC, common to all Rhizobium, are required for synthesis of an oligosaccharide factor, which is converted to a sulphated form (NodRm-1) by the products of the R. meliloti-specific genes nodH and nodQ1-5; NodRm-1 elicits host-specific plant responses [15].
• We describe here a class of closely related ATP-binding proteins, from several bacterial species, which are associated with a variety of cellular functions including membrane transport, cell division, nodulation in Rhizobium and haemolysin export [16].
• Specific binding of proteins from Rhizobium meliloti cell-free extracts containing NodD to DNA sequences upstream of inducible nodulation genes [17].
• Through a random genetic search to find loci that are required for expression of the Rhizobium meliloti nod (nodulation) genes, we isolated a mutant (B4) defective in luteolin-dependent activation of nod gene expression, and found it carries a Tn5 insertion within a chromosomal groEL gene (groELc) located just downstream of a groESc gene [18].
• The Agrobacterium tumefaciens virulence D2 protein is responsible for precise integration of T-DNA into the plant genome [19].

Anatomical context of Rhizobium

• The nodulation-signaling protein NodO from Rhizobium leguminosarum biovar viciae forms ion channels in membranes [20].
• Induction of Rhizobium meliloti nodC expression by plant exudate requires nodD [21].
• Thus, at least for the wheat cell line used in this study, monocotyledonous resistance to Agrobacterium transformation must result from a block to a step of the T-DNA transfer process subsequent to vir induction [22].
• Characterization of flagella genes of Agrobacterium tumefaciens, and the effect of a bald strain on virulence [23].
• In vitro synthesized transferred DNA (T-DNA) complexes comprising single-stranded DNA and Agrobacterium virulence proteins VirD2 and VirE2, essential for plant transformation, were used to stably transfect HeLa cells [24].

Gene context of Rhizobium

• Characterization of the virA locus of Agrobacterium tumefaciens: a transcriptional regulator and host range determinant [25].
• In plants, VIP1 was required for VirE2 nuclear import and Agrobacterium tumorigenicity, participating in early stages of T-DNA expression [26].
• By interspecies hybridization and partial DNA sequencing the gene was found to be homologous to nifA from Klebsiella pneumoniae and Rhizobium meliloti, and to a lesser extent, also to ntrC from K. pneumoniae [27].
• Infection of tobacco cells with an Agrobacterium strain harboring a mutant virD2 allele from which the omega region had been deleted resulted in similar transient expression of gusA mRNA [28].
• Upon inoculation of N. benthamiana leaves with Agrobacterium tumefaciens expressing RPS2, a rapid hypersensitive response (HR) is detected with 22 h of infiltration [29].

Analytical, diagnostic and therapeutic context of Rhizobium

• Site-directed mutagenesis of Cys-82 and His-92 in this motif showed that these residues are essential for Zn2+ and DNA binding activities of Ros. The existence of such a regulator in Agrobacterium may be due to horizontal interkingdom retrotransfer of the ros gene from plant to bacteria [30].
• We also show by a gel mobility-shift assay that overdrive affinity-purified proteins from acetosyringone-induced Agrobacterium cells interact with T-DNA border and overdrive sequences [31].
• The epoxide hydrolase gene from Agrobacterium radiobacter AD1, a bacterium that is able to grow on epichlorohydrin as the sole carbon source, was cloned by means of the polymerase chain reaction with two degenerate primers based on the N-terminal and C-terminal sequences of the enzyme [32].
• By transfer DNA immunoprecipitation (TrIP), we recently showed that T-DNA translocates through the Agrobacterium tumefaciens VirB/D4 T4SS by forming close contacts sequentially with the VirD4 receptor, VirB11 ATPase, the inner membrane subunits VirB6 and VirB8 and, finally, VirB2 pilin and VirB9 [33].
• The entire DNA of Rhizobium meliloti MVII /1 cells was isolated preparatively by gentle lysis and sucrose gradient centrifugation [34].

References