Role of plant root exudate and Sym plasmid-localized nodulation genes in the synthesis by Rhizobium leguminosarum of Tsr factor, which causes thick and short roots on common vetch

Brussel, Audrey; Zaat, Sebastian A. J.; Cremers, H.C.J. Canter; Wijffelman, C. A.; Pees, E.; Tak, T.; Lugtenberg, Ben

doi:10.1128/jb.165.2.517-522.1986

Cited by 126 publications

(62 citation statements)

References 20 publications

(11 reference statements)

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“…However, AVG had no obvious affect on the growth habit ofeither the sym 5 mutants or Sparkle. In addition, the low modulation of the sym 5 mutants is not due to a tsr-like phenotype induced by rhizobia (19), because the sym 5 mutant roots look normal in the absence or presence of rhizobia.…”

Section: Free Acc Content and Ethylene Production In Rootsmentioning

confidence: 99%

“…It is possible that rhizobial infection induces ethylene production in roots, because some strains of Rhizobium leguminosarum can induce thick short roots on the host plant Vicia sativa L. (19). The thick roots and decreased modulation on vetch can be mimicked by exogenous ethylene, and the tsr response to the rhizobia can be overcome by adding AVG,3 an inhibitor of ethylene biosynthesis (22).…”

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confidence: 99%

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Ethylene Inhibitors Restore Nodulation to sym 5 Mutants of Pisum sativum L. cv Sparkle

Fearn

LaRue²

1991

Plant Physiol.

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The sym 5 mutants of pea, Pisum sativum L. cv modulation. When Ag+ is added to the substrate from 4 days before to 4 days after inoculation with rhizobia, nodulation of sym 5 mutants is increased. The roots of the mutant need only be exposed to Ag+ for 4 hours to significantly increase nodule numbers. The content of free 1-aminocyclopropane-1-carboxylic acid and the production of ethylene in the lateral roots of sym 5 mutants do not differ from Sparkle.

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Section: Free Acc Content and Ethylene Production In Rootsmentioning

confidence: 99%

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confidence: 99%

Ethylene Inhibitors Restore Nodulation to sym 5 Mutants of Pisum sativum L. cv Sparkle

Fearn

LaRue²

1991

Plant Physiol.

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“…Root exudates were obtained from plant cultures which were prepared as follows. Six germinated seeds with roots 1.5 cm long were transferred to a support of stainless steel wire netting located 0.5 cm above 25 ml of liquid, deposit-free Jensen medium (41) in sterile culture tubes (28 by 280 mm) plugged with cotton. The cultures were incubated for the indicated period of time at 20°C and 70% relative humidity.…”

Section: Methodsmentioning

confidence: 99%

“…The methods used for surface disinfection and subsequent germination of Vicia sativa L. subsp. nigra (L.) seeds have been described previously (41). Root exudates were obtained from plant cultures which were prepared as follows.…”

Section: Methodsmentioning

confidence: 99%

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A biovar-specific signal of Rhizobium leguminosarum bv. viciae induces increased nodulation gene-inducing activity in root exudate of Vicia sativa subsp. nigra

et al. 1990

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Flavonoids in root exudate of leguminous plants activate the transcription of Rhizobium genes involved in the formation of root nodules (nod genes). We report that inoculation with the homologous symbiont R. kguminosarum bv. viciae results in an increased nod gene-inducing activity (Ini) in root exudate of V. sativa subsp. nigra, whereas inoculation with heterologous Rhizobium strains results in exudates with nod geneinducing activity comparable to that of uninfected plants. Ini can be demonstrated by using either of the isogenic indicator strains containing an inducible nod promoter fused to the Escherichia coli lacZ reporter gene and the regulatory nodD gene of R. leguminosarum bv. viciae, R. leguminosarum bv. trifolii, or R. meliloti. The presence of genes nodDABCEL of R. leguminosarum bv. viciae appeared to be essential for induction of Ini. Mutation of the genes nodI and nodJ causes a delay of Ini, whereas gene nodF appears to be required for both the timely appearance and the maximum level of Ini activity. The nodE gene is responsible for the biovar specificity of induction of Ini by Rhizobium spp. Ini is caused by a soluble heat-stable factor of rhizobial origin. This Rhizobium-produced Ini factor has an apparent molecular weight between 1,000 and 10,000 and does not originate from flavonoid precursors.Induction by Rhizobium bacteria of symbiotic nitrogenfixing root nodules on leguminous plants is a host-specific process; e.g., R. leguminosarum bv. viciae nodulates common vetch, pea, sweet pea, and lentil but not clover or bean, whereas R. leguminosarum bv. trifolii nodulates only clover. Many genes required for root nodule formation (nod genes) by Rhizobium species, including those of R. leguminosarum, are located on a symbiosis (Sym) plasmid. In R. leguminosarum three types of nod genes have been distinguished: (i) a regulatory gene, nodD; (ii) the common nod genes, nodAB-CIJ; and (iii) the genes nodFELMNTO, of which the nodE gene is a host-specific gene which determines whether R. leguminosarum is able to nodulate Vicia or Trifolium plants (3-5, 14, 19, 27, 33). The NodD protein, which is required for activation of the other, inducible nod genes, is only active together with signal molecules, identified as flavonoids, which are exuded by the host plant roots (9,22,25,46 (22,25,46). However, in nature root exudate is not sterile, and we therefore extended our studies to exudate of plants that had been inoculated with Rhizobium spp. (coculture exudate). In this paper, we report that inoculation of Vicia sativa subsp. nigra plants with R. leguminosarum bv. viciae results in significantly increased nod gene-inducing activity (Ini) in coculture exudate. We show that this effect is induced by a biovar-specific extracellular signal of R. leguminosarum bv. viciae. The production of this signal, which is not a flavonoid, requires induction of specific nod genes. MATERIALS AND METHODSBacterial strains, plasmids, and growth conditions. Rhizobium strains and plasmids used in this study are listed in Table 1. Plas...

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Transmembrane orientation and receptor-like structure of the Rhizobium meliloti common nodulation protein NodC

et al. 1988

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The 46.8‐kd NodC protein of Rhizobium meliloti is a membrane protein, essential for nodule formation. Gene fusions of nodC to a portion of the λ cI repressor gene were used to define the membrane‐anchor domain which is necessary for membrane insertion of the NodC protein into the membrane. The transmembrane orientation of NodC was confirmed by surface‐specific radiolabeling and proteolysis experiments. A highly hydrophobic transmembrane‐anchor domain was found near the carboxyl terminus, separating a large extracellular domain which contains an unusual cysteine‐rich cluster from a short putative intracellular domain. Cross‐linking studies showed that the NodC protein exists in the membrane probably as a dimer. The domain structure of the NodC protein shows striking similiarities with cell surface receptors. In nodules of various legumes a truncated form of the NodC protein was detected. The processed NodC was associated with the bacteroids and the amount of this protein increased during nodule development.

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Role of plant root exudate and Sym plasmid-localized nodulation genes in the synthesis by Rhizobium leguminosarum of Tsr factor, which causes thick and short roots on common vetch

Cited by 126 publications

References 20 publications

Ethylene Inhibitors Restore Nodulation to sym 5 Mutants of Pisum sativum L. cv Sparkle

Ethylene Inhibitors Restore Nodulation to sym 5 Mutants of Pisum sativum L. cv Sparkle

A biovar-specific signal of Rhizobium leguminosarum bv. viciae induces increased nodulation gene-inducing activity in root exudate of Vicia sativa subsp. nigra

Transmembrane orientation and receptor-like structure of the Rhizobium meliloti common nodulation protein NodC

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