scholarly journals A Two-Component Regulator Mediates Population-Density-Dependent Expression of the Bradyrhizobium japonicum Nodulation Genes

2002 ◽  
Vol 184 (6) ◽  
pp. 1759-1766 ◽  
Author(s):  
John Loh ◽  
Dasharath P. Lohar ◽  
Brett Andersen ◽  
Gary Stacey
Keyword(s):  
Gene Expression ◽  
Population Density ◽  
Conditioned Medium ◽  
Bradyrhizobium Japonicum ◽  
Response Regulator ◽  
High Population ◽  
Wild Type ◽  
Population Densities ◽  
Density Dependent ◽  
Culture Density

ABSTRACT Bradyrhizobium japonicum nod gene expression was previously shown to be population density dependent. Induction of the nod genes is highest at low culture density and repressed at high population densities. This repression involves both NolA and NodD2 and is mediated by an extracellular factor found in B. japonicum conditioned medium. NolA and NodD2 expression is maximal at high population densities. We demonstrate here that a response regulator, encoded by nwsB, is required for the full expression of the B. japonicum nodYABC operon. In addition, NwsB is also required for the population-density-dependent expression of both nolA and nodD2. Expression of nolA and nodD2 in the nwsB mutant remained at a basal level, even at high culture densities. The nwsB defect could be complemented by overexpression of a second response regulator, NodW. Consistent with the fact that NolA and NodD2 repress nod gene expression, the expression of a nodY-lacZ fusion in the nwsB mutant was unaffected by culture density. In plant assays with GUS fusions, nodules infected with the wild type showed no nodY-GUS expression. In contrast, nodY-GUS expression was not repressed in nodules infected with the nwsB mutant. Nodule competition assays between the wild type and the nwsB mutant revealed that the addition of conditioned medium resulted in a competitive advantage for the nwsB mutant.

scholarly journals Nodulation Gene Regulation and Quorum Sensing Control Density-Dependent Suppression and Restriction of Nodulation in the Bradyrhizobium japonicum-Soybean Symbiosis

2008 ◽  
Vol 74 (12) ◽  
pp. 3749-3756 ◽  
Author(s):  
Siriluck Jitacksorn ◽  
Michael J. Sadowsky
Keyword(s):  
Population Density ◽  
Cell Density ◽  
Bradyrhizobium Japonicum ◽  
Type Strain ◽  
Wild Type Strain ◽  
Inoculum Density ◽  
Complex Medium ◽  
Wild Type ◽  
Soybean Genotype ◽  
Density Dependent

ABSTRACT The nodulation of Glycine max cv. Lambert and the nodulation-restricting plant introduction (PI) genotype PI 417566 by wild-type Bradyrhizobium japonicum USDA110 is regulated in a population-density-dependent manner. Nodulation on both plant genotypes was suppressed (inhibited) when plants received a high-density inoculum (109 cells/ml) of strain USDA110 grown in complex medium, and more nodules were produced on plants receiving a low-cell-density inoculum (105 cells/ml). Since cell-free supernatants from strain USDA110 grown to high cell density in complex medium decreased the expression of an nodY-lacZ fusion, this phenomenon was attributed to bradyoxetin-induced repression of nod gene expression. Inoculation of either the permissive soybean genotype (cv. Lambert) or PI 417566 with 109 cells/ml of the nodD2, nolA, nodW, and nwsB mutants of USDA110 enhanced nodulation (up to 24%) relative to that seen with inoculations done with 105 cells/ml of the mutants or the wild-type strain, indicating that these genes are involved in population-density-dependent nodulation of soybeans. In contrast, the number of nodules produced by an nodD1 mutant on either soybean genotype was less than those seen with the wild-type strain inoculated at a low inoculum density. The nodD2 mutant outcompeted B. japonicum strain USDA123 for nodulation of G. max cv. Lambert at a high or low inoculum density, and the results of root-tip-marking and time-to-nodulate studies indicated that the nolA and nodD2 mutants nodulated this soybean genotype faster than wild-type USDA110. Taken together, the results from these studies indicate that the nodD2 mutant of B. japonicum may be useful to enhance soybean nodulation at high inoculum densities and that NodD2 is a key repressor influencing host-controlled restriction of nodulation, density-dependent suppression of nodulation, perception of bradyoxetin, and competitiveness in the soybean-B. japonicum symbiosis.

Control of dimethylsulfoxide reductase expression in Rhodobacter capsulatus: the role of carbon metabolites and the response regulators DorR and RegA

Microbiology ◽  
2002 ◽  
Vol 148 (2) ◽  
pp. 605-614 ◽  
Author(s):  
Ulrike Kappler ◽  
Wilhelmina M Huston ◽  
Alastair G McEwan
Keyword(s):  
Gene Expression ◽  
Carbon Source ◽  
Rhodobacter Capsulatus ◽  
Response Regulator ◽  
Reductase Activity ◽  
Negative Regulator ◽  
Wild Type ◽  
Dmso Reductase ◽  
Dimethylsulfoxide Reductase ◽  
Operon Expression

Regulation of the expression of dimethylsulfoxide (DMSO) reductase was investigated in the purple phototrophic bacterium Rhodobacter capsulatus. Under phototrophic, anaerobic conditions with malate as carbon source, DMSO caused an approximately 150-fold induction of DMSO reductase activity. The response regulator DorR was required for DMSO-dependent induction and also appeared to slightly repress DMSO reductase expression in the absence of substrate. Likewise, when pyruvate replaced malate as carbon source there was an induction of DMSO reductase activity in cells grown at low light intensity (16 W m−2) and again this induction was dependent on DorR. The level of DMSO reductase activity in aerobically grown cells was elevated when pyruvate replaced malate as carbon source. One possible explanation for this is that acetyl phosphate, produced from pyruvate, may activate expression of DMSO reductase by direct phosphorylation of DorR, leading to low levels of induction of dor gene expression in the absence of DMSO. A mutant lacking the global response regulator of photosynthesis gene expression, RegA, exhibited high levels of DMSO reductase in the absence of DMSO, when grown phototrophically with malate as carbon source. This suggests that phosphorylated RegA acts as a repressor of dor operon expression under these conditions. It has been proposed elsewhere that RegA-dependent expression is negatively regulated by the cytochrome cbb 3 oxidase. A cco mutant lacking cytochrome cbb 3 exhibited significantly higher levels of Φ[dorA::lacZ] activity in the presence of DMSO compared to wild-type cells and this is consistent with the above model. Pyruvate restored DMSO reductase expression in the regA mutant to the same pattern as found in wild-type cells. These data suggest that R. capsulatus contains a regulator of DMSO respiration that is distinct from DorR and RegA, is activated in the presence of pyruvate, and acts as a negative regulator of DMSO reductase expression.

scholarly journals Variation in space and time: a long-term examination of density-dependent dispersal in a woodland rodent

2019 ◽  
Author(s):  
Simon T. Denomme-Brown ◽  
Karl Cottenie ◽  
J. Bruce Falls ◽  
E. Ann Falls ◽  
Ronald J. Brooks ◽  
...  
Keyword(s):  
Time Series ◽  
Population Density ◽  
Local Density ◽  
Spatial Scales ◽  
Deer Mice ◽  
Population Densities ◽  
Density Dependent ◽  
Regional Population ◽  
The Relationship ◽  
Density Dependent Dispersal

AbstractDispersal is a fundamental ecological process that can be affected by population density, yet studies report contrasting effects of density on propensity to disperse. Additionally, the relationship between dispersal and density is seldom examined using densities measured at different spatial scales or over extensive time-series. We used 51-years of trapping data to examine how dispersal by wild deer mice (Peromyscus maniculatus) was affected by changes in both local and regional population densities. We examined these patterns over both the entire time-series and also in ten-year shifting windows to determine whether the nature and strength of the relationship changed through time. Probability of dispersal decreased with increased local and regional population density, and the negative effect of local density on dispersal was more pronounced in years with low regional densities. Additionally, the strength of negative density-dependent dispersal changed through time, ranging from very strong in some decades to absent in other periods of the study. Finally, while females were less likely to disperse, female dispersal was more density-dependent than male dispersal. Our study shows that the relationship between density and dispersal is not temporally static and that investigations of density-dependent dispersal should consider both local and regional population densities.

scholarly journals New Target Genes Controlled by the Bradyrhizobium japonicum Two-Component Regulatory System RegSR

2007 ◽  
Vol 189 (24) ◽  
pp. 8928-8943 ◽  
Author(s):  
Andrea Lindemann ◽  
Annina Moser ◽  
Gabriella Pessi ◽  
Felix Hauser ◽  
Markus Friberg ◽  
...  
Keyword(s):  
Gene Expression ◽  
Nitrogen Fixation ◽  
Bradyrhizobium Japonicum ◽  
Target Genes ◽  
Regulatory Gene ◽  
Wild Type ◽  
Transcription Profiling ◽  
Two Component ◽  
Regulated Gene Expression

ABSTRACT RegSR-like proteins, members of the family of two-component regulatory systems, are present in a large number of proteobacteria in which they globally control gene expression mostly in a redox-responsive manner. The controlled target genes feature an enormous functional diversity. In Bradyrhizobium japonicum, the facultative root nodule symbiont of soybean, RegSR activate the transcription of the nitrogen fixation regulatory gene nifA, thus forming a RegSR-NifA cascade which is part of a complex regulatory network for gene regulation in response to changing oxygen concentrations. Whole-genome transcription profiling was performed here in order to assess the full regulatory scope of RegSR. The comparative analysis of wild-type and ΔregR cells grown under oxic and microoxic conditions revealed that expression of almost 250 genes is dependent on RegR, a result that underscores the important contribution of RegR to oxygen- or redox-regulated gene expression in B. japonicum. Furthermore, transcription profiling of ΔregR bacteroids compared with wild-type bacteroids revealed expression changes for about 1,200 genes in young and mature bacteroids. Incidentally, many of these were found to be induced in symbiosis when wild-type bacteroids were compared with free-living, culture-grown wild-type cells, and they appeared to encode diverse functions possibly related to symbiosis and nitrogen fixation. We demonstrated direct RegR-mediated control at promoter regions of several selected target genes by means of DNA binding experiments and in vitro transcription assays, which revealed six novel direct RegR target promoters.

scholarly journals The Receiver Domain of Hybrid Histidine Kinase VirA: an Enhancing Factor for vir Gene Expression in Agrobacterium tumefaciens

2010 ◽  
Vol 192 (6) ◽  
pp. 1534-1542 ◽  
Author(s):  
Arlene A. Wise ◽  
Fang Fang ◽  
Yi-Han Lin ◽  
Fanglian He ◽  
David G. Lynn ◽  
...  
Keyword(s):  
Gene Expression ◽  
Agrobacterium Tumefaciens ◽  
Histidine Kinase ◽  
Response Regulator ◽  
Multicopy Plasmid ◽  
Wild Type ◽  
Receiver Domain ◽  
Native Promoter ◽  
Cognate Response Regulator ◽  
Hybrid Histidine Kinase

ABSTRACT The plant pathogen Agrobacterium tumefaciens expresses virulence (vir) genes in response to chemical signals found at the site of a plant wound. VirA, a hybrid histidine kinase, and its cognate response regulator, VirG, regulate vir gene expression. The receiver domain at the carboxyl end of VirA has been described as an inhibitory element because its removal increased vir gene expression relative to that of full-length VirA. However, experiments that characterized the receiver region as an inhibitory element were performed in the presence of constitutively expressed virG. We show here that VirA's receiver domain is an activating factor if virG is expressed from its native promoter on the Ti plasmid. When virAΔR was expressed from a multicopy plasmid, both sugar and the phenolic inducer were essential for vir gene expression. Replacement of wild-type virA on pTi with virAΔR precluded vir gene induction, and the cells did not accumulate VirG or induce transcription of a virG-lacZ fusion in response to acetosyringone. These phenotypes were corrected if the virG copy number was increased. In addition, we show that the VirA receiver domain can interact with the VirG DNA-binding domain.

scholarly journals Evolution under pH stress and high population densities leads to increased density‐dependent fitness in the protist Tetrahymena thermophila

Evolution ◽  
2020 ◽  
Vol 74 (3) ◽  
pp. 573-586 ◽  
Author(s):  
Felix Moerman ◽  
Angelina Arquint ◽  
Stefanie Merkli ◽  
Andreas Wagner ◽  
Florian Altermatt ◽  
...  
Keyword(s):  
Tetrahymena Thermophila ◽  
High Population ◽  
Population Densities ◽  
Density Dependent ◽  
Ph Stress

Contrasts in body size and growth suggest that high population density results in faster pace of life in Damaraland mole-rats (Fukomys damarensis)

2018 ◽  
Vol 96 (8) ◽  
pp. 920-927 ◽  
Author(s):  
K.T. Finn ◽  
D.M. Parker ◽  
N.C. Bennett ◽  
M. Zöttl
Keyword(s):  
Body Size ◽  
Population Density ◽  
Litter Size ◽  
Group Size ◽  
Growth Rates ◽  
High Population ◽  
Low Density ◽  
High Population Density ◽  
Population Densities ◽  
Study Sites

We studied the correlates of population density and body size, growth rates, litter size, and group size in Damaraland mole-rats (Fukomys damarensis (Ogilby, 1838)) at two study sites with contrasting population densities. Group size, litter size, and the probability of recapture were independent of study site. However, body size differed between the two study sites, suggesting that population density may affect life-history traits in social mole-rats. At the low-density site (0.13 groups/ha), individuals were significantly larger and subordinate males showed higher growth rates than at the high-density site (0.41 groups/ha), which may indicate that high population density in subterranean rodents enhances pace of life. The larger size of nonreproductive individuals at the low-density site could adapt individuals at lower population densities to larger dispersal distances.

scholarly journals Sensory neurons control heritable adaptation to stress through germline reprogramming

2018 ◽  
Author(s):  
Giusy Zuco ◽  
Vikas Kache ◽  
Pedro Robles ◽  
Jyotiska Chaudhuri ◽  
Beth Hill ◽  
...  
Keyword(s):  
Population Density ◽  
Histone Modifications ◽  
Methylation Status ◽  
Female Offspring ◽  
High Population ◽  
Environmental Cues ◽  
List Type ◽  
Histone Demethylases ◽  
Germline Transmission ◽  
Population Densities

AbstractMaternal neuronal signaling has been reported to program adaptive changes in offspring physiology in diverse organisms [1, 2]. However, the mechanisms for the inheritance of adaptive maternal effects through the germline are largely unknown. In the nematode Auanema freiburgensis, stress-resistance and sex of the offspring depend on environmental cues experienced by the mother. Maternal sensing of high population densities results in the production of stress-resistant larvae (dauers) that develop into hermaphrodites. Ablation of the maternal ASH chemosensory neurons results only in non-dauer offspring that develop into males or females. High population densities correlate with changes in the methylation status of H3K4 and H3K9 in the maternal germline. Inhibition of JMJD histone demethylases prevents mothers from producing dauers and hermaphrodite offspring in high-density conditions. Our results demonstrate a case of soma-to-germline transmission of environmental information that influences the phenotype of the following generation through changes in histone modifications of the maternal germline.HighlightsHigh population density leads to the production of hermaphrodite offspring.The ASH neuron in the hermaphrodite mother senses population density.Histone modifications in the maternal germline correlate with the sex of offspring.Inhibition of histone demethylases results in female offspring in all conditions.

scholarly journals Evolution under pH stress and high population densities leads to increased density-dependent fitness in the protist Tetrahymena thermophila

2019 ◽  
Author(s):  
Felix Moerman ◽  
Angelina Arquint ◽  
Stefanie Merkli ◽  
Andreas Wagner ◽  
Florian Altermatt ◽  
...  
Keyword(s):  
Abiotic Stress ◽  
Tetrahymena Thermophila ◽  
Low Ph ◽  
High Population ◽  
Population Densities ◽  
Density Dependent ◽  
Ph Stress ◽  
Evolutionary Changes ◽  
Ph Conditions ◽  
Protist Species

AbstractAbiotic stress is a major force of selection that organisms are constantly facing. While the evolutionary effects of various stressors have been broadly studied, it is only more recently that the relevance of interactions between evolution and underlying ecological conditions, that is, eco-evolutionary feedbacks, have been highlighted. Here, we experimentally investigated how populations adapt to pH-stress under high population densities. Using the protist species Tetrahymena thermophila, we studied how four different genotypes evolved in response to stressfully low pH conditions and high population densities. We found that genotypes underwent evolutionary changes, some shifting up and others shifting down their intrinsic rates of increase (r0). Overall, evolution at low pH led to the convergence of r0 and intraspecific competitive ability (α) across the four genotypes. Given the strong correlation between r0 and α, we argue that this convergence was a consequence of selection for increased density-dependent fitness at low pH under the experienced high density conditions. Increased density-dependent fitness was either attained through increase in r0, or decrease of α, depending on the genetic background. In conclusion, we show that demography can influence the direction of evolution under abiotic stress.

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