Conservation of extended promoter regions of nodulation genes in
            <i>Rhizobium</i>

Rostas, Katalin; Kondorosi, Éva; Horváth, Beatrix; Simoncsits, András; Kondorosi, Ádám

doi:10.1073/pnas.83.6.1757

Cited by 201 publications

(135 citation statements)

References 20 publications

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“…In contrast to other Bradyrhizobium nod (7,27) and Rhizobium nod and hsn (35) gene loci, the nolA gene locus did not hybridize or have sequence similarity to the 25-mer nod box consensus sequence (7,27), which has been implicated to have a role in the coordinated regulation of nodulation genes (35). This suggests that nolA, and several other B. japonicum nodulation genes, may be regulated by nod-box-independent promoters (7,27 patibility between nolA and the indigenous nodulation and nitrogen fixation genes (42).…”

Section: Resultsmentioning

confidence: 88%

“…1). Sequences present on pMJS12 did not hybridize to B. japonicum nodDI YABC' (pMJS18), R. meliloti hsnABCD, or Nod box consensus sequence gene probes (7,35 To determine whether a functional nodulation complementing GSN DNA region was unique to strain USDA 110, we made a genomic DNA library from strain DE3-la [nodulation unrestricted, serogroup 127 (5, 25)] and mated cosmid clones which hybridized to the pMJS12 gene probe to strain SD6-lc. One of the transconjugants, SD6-lc(pFR27), was found to nodulate PI 377578 (mean of 22 nodules per plant) to the same extent as DE3-la.…”

Section: Resultsmentioning

confidence: 99%

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The Bradyrhizobium japonicum nolA gene and its involvement in the genotype-specific nodulation of soybeans.

Sadowsky

Cregan

Göttfert

et al. 1991

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

139

115

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Several soybean genotypes have been identified which specifically exclude modulation by members of Bradyrhizobiumjaponicum serocluster 123. We have identified and sequenced a DNA region from B. japonicum strain USDA 110 which is involved in genotype-specifc modulation of soybeans. This 2.3-kilobase region, cloned in pMJS12, allows B. japonicum serocluster 123 isolates to form nodules on plants of serogroup 123-restricting genotypes. The nodules, however, were ineffective for symbiotic nitrogen fixation. The nodulation-complementing region is located approximately 590 base pairs transcriptionally downstream from nodD2. The 5' end of pMJS12 contains a putative open reading frame (ORF) of 710 base pairs, termed nowl. Transposon Tn3-HoHo mutations only within the ORF abolished modulation complementation. The N terminus of the predicted noL4 gene product has strong similarity with the N terminus of MerR, the regulator of mercury resistance genes. Translational IacZ fusion experiments indicated that nolA was moderately induced by soybean seed extract and the isoflavone genistein. Restriction fragments that hybridize to pMJS12 were detected in genomic DNAs from both nodulation-restricted and -unrestricted strains.

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Section: Resultsmentioning

confidence: 88%

Section: Resultsmentioning

confidence: 99%

The Bradyrhizobium japonicum nolA gene and its involvement in the genotype-specific nodulation of soybeans.

Sadowsky

Cregan

Göttfert

et al. 1991

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

139

115

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“…In previous studies, TnS-induced mutations did not show a polar effect on genes located downstream of the insertion site because of constitutive expression of these genes via promoter elements located within the transposon, which were shown to be active in R meliloti (24). In the present analysis of the nodM::TnS insertion mutants in an overproducing background, we could not exclude the possibility that the levels of constitutive expression of the downstream nolF, no1G, nolH, nolI, and nodN genes from the TnS promoter were lower than those of the other upregulated nod genes.…”

Section: Discussionmentioning

confidence: 96%

Rhizobium nodM and nodN genes are common nod genes: nodM encodes functions for efficiency of nod signal production and bacteroid maturation

et al. 1992

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Earlier, we showed that Rhizobium meliloi nod&f codes for glucosamine synthase and that nodM and nodN mutants produce strongly reduced root hair deformation activity and display delayed nodulation of Medicago sativa (Baev et al., Mol. Gen. Genet. 228:113-124, 1991). Here, we demonstrate that nodPf and nodN genes from Rhizobium leguminosarum biovar viciae restore the root hair deformation activity of exudates of the corresponding R. meliloti mutant strains. Partial restoration of the nodulation phenotypes of these two strains was also observed. In nodulation assays, galactosamine and N-acetylglucosamine could substitute for glucosamine in the suppression of the R. melilot nodM mutation, although N-acetylglucosamine was less efficient. We observed that in nodules induced by nodM mutants, the bacteroids did not show complete development or were deteriorated, resulting in decreased nitrogen fixation and, consequently, lower dry weights of the plants. This mutant phenotype could also be suppressed by exogenously supplied glucosamine, N-acetylglucosamine, and galactosamine and to a lesser extent by glucosamine-6-phosphate, indicating that the nodAf mutant bacteroids are limited for glucosamine. In addition, by using derivatives of the wild type and a nod&t mutant in which the nod genes are expressed at a high constitutive level, it was shown that the nodM mutant produces significantly fewer Nod factors than the wild-type strain but that their chemical structures are unchanged. However, the relative amounts of analogs of the cognate Nod signals were elevated, and this may explain the observed host range effects of the nodM mutation. Our data indicate that both the nod&f and nodN genes of the two species have common functions and confirm that NodM is a glucosamine synthase with the biochemical role of providing sufficient amounts of the sugar moiety for the synthesis of the glucosamine oligosaccharide signal molecules.Rhizobia are capable of establishing symbiotic associations with their legume hosts. During this process, the bacteria undergo rapid developmental changes in order to make the transition from a soil environment through the root surface environment to a new ecological niche inside the plant host cells. The partnership between a given plant host and its microsymbiont is highly specific; most leguminous plants can be nodulated by a more or less limited number of Rhizobium species. For example, Rhizobium meliloti nodulates species of the genera Medicago, Meliotus, and Trigonella (11).Numerous bacterial and plant genes are expressed specifically during nodule development (19 Lerouge and coworkers (17) identified a major alfalfa-specific signal molecule as an acylated and sulfated glucosamine tetrasaccharide. Using a similar approach, we showed that R meliloti produces a family of biologically active Nod signal molecules (26). Host-specific signal molecules secreted by Rhizobium leguminosarum have also been identified (30).In different rhizobia, common and host-specific nod genes have been identified (12). The b...

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“…Fractions were assayed for inducing activity by adding 1.5 ml of a fraction (or dilutions of a fraction) to (24). RESULTS In several Rhizobium and Bradyrhizobium strains, the nodABC genes form an operon preceded by a conserved DNA sequence, the "nod box" (15,25,26), which is located near the transcription initiation site (27). In USDA 123, a 4.3-kilobase HindIII fragment contains nodD, the nod box, a potential open reading frame (or]), nodA, nodB, and the amino-terminal end of nodC (E.R.A., J.B., and D. Thompson, unpublished data).…”

Section: Methodsmentioning

confidence: 99%

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.

368

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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Conservation of extended promoter regions of nodulation genes in Rhizobium

Cited by 201 publications

References 20 publications

The Bradyrhizobium japonicum nolA gene and its involvement in the genotype-specific nodulation of soybeans.

The Bradyrhizobium japonicum nolA gene and its involvement in the genotype-specific nodulation of soybeans.

Rhizobium nodM and nodN genes are common nod genes: nodM encodes functions for efficiency of nod signal production and bacteroid maturation

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

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