Nucleotide Sequence ofRhizobium meliloti1021 Nodulation Genes:nodDIs Read Divergently fromnodABC

Egelhoff, Thomas; Fisher, Robert F.; Jacobs, Thomas; Mulligan, John T.; Long, Sharon R.

doi:10.1089/dna.1985.4.241

Cited by 165 publications

(90 citation statements)

References 25 publications

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“…However, by sequence comparison ihis ORF is not related to nifE. The R. meliloti nifE gene, mapping adjacent to nifHDK (H. Reilander, unpublished data), is separated from nifN by an intervening sequence which contains most of the nodulation genes (15,18). To date, R. meliloti is the only known nitrogen-fixing organism in which the genes nifE and nifN are separated.…”

Section: Discussionmentioning

confidence: 99%

Rhizobium meliloti nifN (fixF) gene is part of an operon regulated by a nifA-dependent promoter and codes for a polypeptide homologous to the nifK gene product

et al. 1987

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An essential gene for symbiotic nitrogen fixation (fixF) is located near the common nodulation region of Rhizobium melioti. A DNA fragment carrying fixF was characterized by hybridization with Klebsiella pneumoniae nif DNA and by nucleotide sequence analysis. The fixF gene was found to be related to K. pneumoniae nifVN and was therefore renamed as the R. melioti nifN gene. Upstream of the nifN coding region a second open reading frame was identified coding for a putative polypeptide of 110 amino acids (ORF110). By fragment-specific Tn5 mutagenesis it was shown that the nijN gene and ORF110 form an operon. The control region of this operon contains a nif promoter and also the putative nifA-binding sequence. For the deduced amino acid sequence of the nifN gene product a striking homology to the R. meliloti ni:K protein was found. One cysteine residue and its adjacent amino acid sequence, which are highly conserved in the R. meliloti niJK, R. meliloti nijN, and K. pneumoniae niJN proteins, may play a role in binding the FeMo cofactor.

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Section: Discussionmentioning

confidence: 99%

Rhizobium meliloti nifN (fixF) gene is part of an operon regulated by a nifA-dependent promoter and codes for a polypeptide homologous to the nifK gene product

et al. 1987

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“…Two primers, NodD1:S1-XbaI (5Ј-GCTCTAGATAACGAGGGCAAAAAATGCGTTAGGG GCCTAG-3Ј) and NodD1:AS1-SalI (5Ј-CGGTCGACCACAGGTGTCCGACT AGG-3Ј), were designed to contain unique XbaI and SalI sites, respectively, for subsequent cloning of PCR products. nodD1 was amplified by PCR using cloned Pfu DNA polymerase (Stratagene) and pRmE39, which contains the entire nodD1 coding sequence (6). Primer NodD1:AS1-SalI was designed to remove the C-terminal stop codon to create an in-frame fusion of NodD1 to the Streptag (Biometra) (36), termed NodD1-ST. pNodD1-ST was constructed by cloning this XbaI-SalI PCR product into pASK75B after digestion with XbaI and SalI (39).…”

Section: Methodsmentioning

confidence: 99%

Luteolin and GroESL Modulate In Vitro Activity of NodD

2002

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In the early stages of symbiosis between the soil bacterium Sinorhizobium meliloti and its leguminous host plant, alfalfa, bacterial nodulation (nod) genes are controlled by NodD1, NodD2, and NodD3, members of the LysR family of transcriptional regulators, in response to flavonoid and other inducers released by alfalfa. To gain an understanding of the biochemical aspects of this action, epitope-tagged recombinant NodD1 and NodD3 were overexpressed in Escherichia coli. The DNA binding properties of the purified recombinant NodD proteins were indistinguishable from those of NodD isolated from S. meliloti. In addition, the E. coli GroEL chaperonin copurified with the recombinant NodD proteins. In this study, we showed that NodD proteins are in vitro substrates of the GroESL chaperonin system and that their DNA binding activity is modulated by GroESL. This confirmed the earlier genetic implication that the GroESL chaperonin system is essential for the function of these regulators. Increased DNA binding activity by NodD1 in the presence of luteolin confirmed that NodD1 is involved in recognizing the plant signal during the early stages of symbiosis.

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“…In three agronomically important Rhizobium/legume associations, R. trifolii/clover, R. meliloti/alfalfa, and R. leguminosarum/pea, important bacterial nodulation genes (1)(2)(3)(4) and plant compounds that induce them (5-7) have been identified. In these associations flavones (5)(6)(7) or flavanones (7) have been found to induce the nodABC genes, as well as other nod genes involved in host specificity (1).…”

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Induction of Bradyrhizobium japonicum common nod genes by isoflavones isolated from Glycine max

Kosslak¹,

Bookland²,

Barkei³

et al. 1987

Proc. Natl. Acad. Sci. U.S.A.

375

225

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The early events in legume nodulation by Rhizobium spp. involve a conserved gene cluster known as the common nod region. A broad-host-range plasmid (pEA2-21) containing a Bradyrhizobium japonicum nodDABC-acZ translational fusion was constructed and used to monitor nod gene expression in response to soybean root extract. Two inducing compounds were isolated and identified. Analysis using ultraviolet absorption spectra, proton nuclear magnetic resonance, and mass spectrometry showed that the two inducers were 4',7-dihydroxyisoflavone (daidzein) and 4',5,7-trihydroxyisoflavone (genistein). Induction was also seen with some, but not all, of the flavonoid compounds that induce nod genes in fast-growing Rhizobium strains that nodulate clover, alfalfa, or peas. When pEA2-21 was introduced into Rhizobium trifohii, it was inducible by flavones but not by daidzein and genistein. In Rhizobium fredii, pEA2-21 was induced by isoflavones and flavones. Thus, the specificity of induction appears to be influenced by the host-strain genome.Members of the bacterial genus Rhizobium form symbiotic associations with leguminous plants that result in the formation of nitrogen-fixing root nodules. In three agronomically important Rhizobium/legume associations, R. trifolii/clover, R. meliloti/alfalfa, and R. leguminosarum/pea, important bacterial nodulation genes (1-4) and plant compounds that induce them (5-7) have been identified. In these associations flavones (5-7) or flavanones (7) have been found to induce the nodABC genes, as well as other nod genes involved in host specificity (1). Isoflavones have been found to inhibit the induction of nodABC in R. leguminosarum (7).The Bradyrhizobium japonicum/soybean symbiosis is of considerable agricultural importance. In contrast to Rhizobium spp., Bradyrhizobium species are slow-growing (8), nitrogen-fixation and nodulation genes are located on the chromosome (9) and not on plasmids (10)(11)(12), and less is known about the genetic requirements for nodulation (13)(14)(15). In particular, the compounds produced by the soybean host that interact with the common nod genes have not been characterized.In this study, a nodABC-lacZ translational fusion was used to monitor nod gene expression in B. japonicum in response to soybean root extract. Two major components from soybeans (Glycine max cv. Williams) were isolated that induced the expression of the nodABC-lacZ fusion when it was present in the soybean-nodulating bacteria B. japonicum and Rhizobium fredii, but not when it was present in R. trifolii. MATERIALS AND METHODSStrains and Plasmids. Standard procedures (16) were used for DNA manipulations. A HindIII fragment containing the nod region of B. japonicum USDA 123 was cloned in both orientations into the single HindIII site of plC19R (17). BamHI-Bgl II fragments containing the nod genes and flanking polylinker sequences were then cloned into the BamHI site of the broad-host-range vector pGD926 (18) resulting in pEA2-21 and pEA4-10 (Fig. 1) (19) agar and germinated for 3 days in the d...

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Nucleotide Sequence ofRhizobium meliloti1021 Nodulation Genes:nodDIs Read Divergently fromnodABC

Cited by 165 publications

References 25 publications

Rhizobium meliloti nifN (fixF) gene is part of an operon regulated by a nifA-dependent promoter and codes for a polypeptide homologous to the nifK gene product

Rhizobium meliloti nifN (fixF) gene is part of an operon regulated by a nifA-dependent promoter and codes for a polypeptide homologous to the nifK gene product

Luteolin and GroESL Modulate In Vitro Activity of NodD

Induction of Bradyrhizobium japonicum common nod genes by isoflavones isolated from Glycine max

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