Nodulation Gene Regulation in<i>Bradyrhizobium japonicum</i>: a Unique Integration of Global Regulatory Circuits

Loh, John T.; Stacey, Gary

doi:10.1128/aem.69.1.10-17.2003

Cited by 100 publications

(87 citation statements)

References 77 publications

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“…This indicates that the bacterial strains can compete with existing natural bacteria, which is understandable as they are isolated from similar soil conditions in Korea. Although such a competition with indigenous less-effective rhizobia was studied in rhizobial inoculant (Sessitch et al 2002, Lopez-Gracia et al 2002, Loh and Stacey 2003, competition in PGPR inoculants was not intensively explored probably because some PGPR inoculants are selected for increasing plant systemic acquired resistance or for suppression of pathogenic bacteria (Zehnden et al 2001, Anith et al 2004. Bacteria inoculation, which can improve P and K availability in soils by producing organic acids and other chemicals, stimulated growth and mineral uptake of plants (Alexander 1977, Park et al 2003.…”

Section: Resultsmentioning

confidence: 99%

Effect of co-inoculation with phosphate and potassium solubilizing bacteria on mineral uptáme and growth of pepper and cucumber

Han¹,

Supanjani²,

Lee³

2006

PLANT SOIL ENVIRON

294

123

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Biofertilizers have been used as sources to improve plant nutrients in sustainable agriculture. Experiments were conducted to evaluate the potential of phosphate solubilizing bacteria (PSB) Bacillus megaterium var. phosphaticum and potassium solubilizing bacteria (KSB) Bacillus mucilaginosus inoculated in nutrient limited soil planted with pepper and cucumber. Results showed that rock P and K applied either singly or in combination did not significantly enhance soil availability of P and K, indicating their unsuitability for direct application. PSB was a more potent P-solubilizer than KSB, and co-inoculation of PSB and KSB resulted in consistently higher P and K availability than in the control without bacterial inoculum and without rock material fertilizer. Integrated rock P with inoculation of PSB increased the availability of P and K in soil, the uptake of N, P and K by shoot and root, and the growth of pepper and cucumber. Similar but less pronounced results were obtained when rock K and KSB were added concomitantly. Combined together, rock materials and both bacterial strains consistently increased further mineral availability, uptake and plant growth of pepper and cucumber, suggesting its potential use as fertilizer.

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Section: Resultsmentioning

confidence: 99%

Effect of co-inoculation with phosphate and potassium solubilizing bacteria on mineral uptáme and growth of pepper and cucumber

Han¹,

Supanjani²,

Lee³

2006

PLANT SOIL ENVIRON

294

123

View full text Add to dashboard Cite

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“…Nodulation requires induction of nod gene expression; however, efficient symbiosis with host plants occurs only when these genes are expressed in an appropriate quantitative, spatial, and temporal pattern and involves both positive and negative regulation (7,8,35). Mutations that alter either positive or negative regulation of nod genes result in aberrant and delayed nodulation phenotypes.…”

Section: Discussionmentioning

confidence: 99%

“…The development of nitrogen-fixing nodules by rhizobia involves a variety of interactions between the plant and microbe; however, at the center of this process are a set of nod (nodulation) genes required for the synthesis of oligosaccharide-nodulation factors, for determining host-plant specificity, and for optimizing the efficiency of symbiosis (4-6). Successful interaction between the rhizobium and host plant requires expression of both positive and negative transcriptional control of genes related to nodulation and symbiosis (7,8 …”

mentioning

confidence: 99%

Structural basis for regulation of rhizobial nodulation and symbiosis gene expression by the regulatory protein NolR

Lee

Krishnan

Jez

2014

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

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The symbiosis between rhizobial microbes and host plants involves the coordinated expression of multiple genes, which leads to nodule formation and nitrogen fixation. As part of the transcriptional machinery for nodulation and symbiosis across a range of Rhizobium, NolR serves as a global regulatory protein. Here, we present the X-ray crystal structures of NolR in the unliganded form and complexed with two different 22-base pair (bp) double-stranded operator sequences (oligos AT and AA). Structural and biochemical analysis of NolR reveals protein-DNA interactions with an asymmetric operator site and defines a mechanism for conformational switching of a key residue (Gln56) to accommodate variation in target DNA sequences from diverse rhizobial genes for nodulation and symbiosis. This conformational switching alters the energetic contributions to DNA binding without changes in affinity for the target sequence. Two possible models for the role of NolR in the regulation of different nodulation and symbiosis genes are proposed. To our knowledge, these studies provide the first structural insight on the regulation of genes involved in the agriculturally and ecologically important symbiosis of microbes and plants that leads to nodule formation and nitrogen fixation.transcription factor | protein structure T he symbiosis between rhizobial bacteria from the Rhizobium, Sinorhizobium, Mesorhizobium, Azorhizobium, and Bradyrhizobium genera and leguminous plants leads to the formation of root nodules (1, 2). These plant organs are specialized for nitrogen fixation and assimilation and are of major ecological and agricultural importance. For example, nitrogen-fixing nodules account for one quarter of total nitrogen fixed globally each year (3). The development of nitrogen-fixing nodules by rhizobia involves a variety of interactions between the plant and microbe; however, at the center of this process are a set of nod (nodulation) genes required for the synthesis of oligosaccharide-nodulation factors, for determining host-plant specificity, and for optimizing the efficiency of symbiosis (4-6). Successful interaction between the rhizobium and host plant requires expression of both positive and negative transcriptional control of genes related to nodulation and symbiosis (7,8

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“…viciae, trifolii and phaseoli, R. etli, Rhizobium sp. strain NGR234, and S. meliloti, produce various AHL compounds (see reviews by Wisniewski-Dye and Downie 2002; Gonzales and Marketon 2003); whereas, B. japonicum produces bradyoxetin, a non-AHL signal molecule (Loh et al 2002a, b;Loh and Stacey, 2003). The most studied quorum sensing is associated with R. leguminosarum, in which the synthesis of 10 AHLs is directed by four LuxI homologs (i.e., CinI, RhiI, TraI and RaiI) (Lithgow et al 2000;Wisniewski-Dye and Downie 2002).…”

Section: Nod Factor Quorum Sensing and Its Relevance To Inoculant Promentioning

confidence: 99%

Exploiting inter-organismal chemical communication for improved inoculants

Mabood¹,

Gray²,

Lee³

et al. 2006

Can. J. Plant Sci.

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[951][952][953][954][955][956][957][958][959][960][961][962][963][964][965][966]. The combination of rising fossil fuel prices and a need to reduce greenhouse gas emissions will lead to expanded use of crop inoculants (bio-fertilizers) both for increased production of biomass (for bio-fuels and soil C storage) and to reduce production of nitrous oxide, through increased reliance on biological nitrogen fixation. Over the last century inoculants have been improved through strain selection, improved carriers (including sterile carriers), and increased cell densities. During the last few decades our understanding of signalling between symbiotic bacteria and plants has expanded enormously, with the signalling between rhizobia and their legume hosts being the model system. Recent work has shown that adverse environmental conditions can inhibit this signalling and that addition of plant-to-microbe signals into inoculants can help overcome this. This is also true of addition of the microbe-to-plant signals that act as the return signals of this system; however, they have also been shown to cause a general and direct stimulation of plant growth that is not yet well understood. Finally, very recent work has shown that some of the plant growth-promoting rhizobacteria produce novel signal compounds that stimulate plant growth. This is a time of rapid increase in understanding with regard to plant-microbe signalling; the use of these signals in commercial inoculants offers a new wave in innovations for this industry at a time when there is great need.Key words: Inoculants, rhizobacteria, rhizobia, signalling Mabood, F., Gray, E. J., Lee, K. D., Supanjani, et Smith D. L. 2006. Exploitation de la médiation chimique entre les organismes pour créer de meilleurs inoculants. Can. J. Plant Sci. 86: 951-966. La hausse du prix des combustibles fossiles et la néces-sité de réduire les émissions de gaz à effet de serre déboucheront sur une utilisation accrue des inoculants en agriculture (engrais biologiques) pour la production d'une plus grande quantité de biomasse (pour les biocarburants et le stockage du carbone dans le sol) mais aussi pour la réduction des dégagements d'oxydes nitreux par un plus grand recours à des mécanismes biologiques pour fixer l'azote dans le sol. Au cours du siècle dernier, on a raffiné les inoculants par la sélection, amélioré les excipients (y compris les substrats stériles) et accru la population de cellules. Durant les quelque dernières décennies, nos connaissances sur les signaux que s'échangent microorganismes et végétaux en symbiose se sont considérablement élargies et le système de signalisation entre les rhizobiums et les légumineuses qui sont leur hôte est devenu un modèle du genre. Des recherches récentes indiquent que des conditions environnementales difficiles peuvent nuire à l'échange de signaux et qu'on peut surmonter ce problème en ajoutant des médiateurs plante-microorganisme à l'inoculant. La même remarque s'applique à l'addition de médiateurs microorganisme-plante qui véhiculent la répons...

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Nodulation Gene Regulation inBradyrhizobium japonicum: a Unique Integration of Global Regulatory Circuits

Cited by 100 publications

References 77 publications

Effect of co-inoculation with phosphate and potassium solubilizing bacteria on mineral uptáme and growth of pepper and cucumber

Effect of co-inoculation with phosphate and potassium solubilizing bacteria on mineral uptáme and growth of pepper and cucumber

Structural basis for regulation of rhizobial nodulation and symbiosis gene expression by the regulatory protein NolR

Exploiting inter-organismal chemical communication for improved inoculants

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