scholarly journals Identification and Characterization of Genes Required for Early Myxococcus xanthus Developmental Gene Expression

2000 ◽  
Vol 182 (16) ◽  
pp. 4564-4571 ◽  
Author(s):  
Dongchuan Guo ◽  
Yun Wu ◽  
Heidi B. Kaplan
Keyword(s):  
Response Regulator ◽  
Myxococcus Xanthus ◽  
Normal Growth ◽  
Negative Regulator ◽  
Developmental Expression ◽  
Wild Type ◽  
Developmental Gene ◽  
O Antigen ◽  
New Genes ◽  
Positive Regulators

ABSTRACT Starvation and cell density regulate the developmental expression of Myxococcus xanthus gene 4521. Three classes of mutants allow expression of this developmental gene during growth on nutrient agar, such that colonies of strains containing a Tn5 lac Ω4521 fusion are Lac+. One class of these mutants inactivates SasN, a negative regulator of 4521expression; another class activates SasS, a sensor kinase-positive regulator of 4521 expression; and a third class blocks lipopolysaccharide (LPS) O-antigen biosynthesis. To identify additional positive regulators of 4521 expression, 11 Lac− TnV.AS transposon insertion mutants were isolated from a screen of 18,000 Lac+ LPS O-antigen mutants containing Tn5 lac Ω4521 (Tcr). Ten mutations identified genes that could encode positive regulators of4521 developmental expression based on their ability to abolish 4521 expression during development in the absence of LPS O antigen and in an otherwise wild-type background. Eight of these mutations mapped to the sasB locus, which encodes the known 4521 regulators SasS and SasN. One mapped tosasS, whereas seven identified new genes. Three mutations mapped to a gene encoding an NtrC-like response regulator homologue, designated sasR, and four others mapped to a gene designated sasP. One mutation, designatedssp10, specifically suppressed the LPS O-antigen defect; the ssp10 mutation had no effect on 4521expression in an otherwise wild-type background but reduced4521 developmental expression in the absence of LPS O antigen to a level close to that of the parent strain. All of the mutations except those in sasP conferred defects during growth and development. These data indicate that a number of elements are required for 4521 developmental expression and that most of these are necessary for normal growth and fruiting body development.

scholarly journals act Operon Control of Developmental Gene Expression in Myxococcus xanthus

2002 ◽  
Vol 184 (4) ◽  
pp. 1172-1179 ◽  
Author(s):  
Thomas M. A. Gronewold ◽  
Dale Kaiser
Keyword(s):  
Fruiting Body ◽  
Myxococcus Xanthus ◽  
The Other ◽  
Loss Of Function ◽  
Wild Type ◽  
Developmental Gene ◽  
Developmental Gene Expression ◽  
Mutant Strains ◽  
Genes Encoding ◽  
Signal Production

ABSTRACT Cell-bound C-signal guides the building of a fruiting body and triggers the differentiation of myxospores. Earlier work has shown that transcription of the csgA gene, which encodes the C-signal, is directed by four genes of the act operon. To see how expression of the genes encoding components of the aggregation and sporulation processes depends on C-signaling, mutants with loss-of-function mutations in each of the act genes were investigated. These mutations were found to have no effect on genes that are normally expressed up to 3 h into development and are C-signal independent. Neither the time of first expression nor the rate of expression increase was changed in actA, actB, actC, or actD mutant strains. Also, there was no effect on A-signal production, which normally starts before 3 h. By contrast, the null act mutants have striking defects in C-signal production. These mutations changed the expression of four gene reporters that are related to aggregation and sporulation and are expressed at 6 h or later in development. The actA and actB null mutations substantially decreased the expression of all these reporters. The other act null mutations caused either premature expression to wild-type levels (actC) or delayed expression (actD), which ultimately rose to wild-type levels. The pattern of effects on these reporters shows how the C-signal differentially regulates the steps that together build a fruiting body and differentiate spores within it.

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.

Mutations at the suppressor of forked locus increase the accumulation of gypsy-encoded transcripts in Drosophila melanogaster

1986 ◽  
Vol 6 (6) ◽  
pp. 2271-2274
Author(s):  
S M Parkhurst ◽  
V G Corces
Keyword(s):  
Drosophila Melanogaster ◽  
Transposable Element ◽  
Negative Regulator ◽  
Developmental Expression ◽  
Wild Type ◽  
Stages Of Development

We studied the effect of mutations at the suppressor of forked [su(f)] locus in Drosophila melanogaster on the accumulation of transcripts encoded by the gypsy transposable element. Mutations at this locus do not affect the pattern of developmental expression of gypsy, but they cause an increase in the total amount of gypsy RNA present at different stages of development as compared with wild-type or su(f)/+ flies. These results suggest that the su(f)-encoded products acts as a negative regulator of gypsy expression.

scholarly journals An Adenylyl Cyclase, CyaA, of Myxococcus xanthus Functions in Signal Transduction during Osmotic Stress

2002 ◽  
Vol 184 (13) ◽  
pp. 3578-3585 ◽  
Author(s):  
Yoshio Kimura ◽  
Yukako Mishima ◽  
Hiromi Nakano ◽  
Kaoru Takegawa
Keyword(s):  
Osmotic Stress ◽  
Adenylyl Cyclase ◽  
Spore Germination ◽  
Developmental Stages ◽  
Catalytic Domain ◽  
Myxococcus Xanthus ◽  
Normal Growth ◽  
Wild Type ◽  
Amino Terminal ◽  
Mutant Cells

ABSTRACT An adenylyl cyclase gene (cyaA) present upstream of an osmosensor protein gene (mokA) was isolated from Myxococcus xanthus. cyaA encoded a polypeptide of 843 amino acids with a predicted molecular mass of 91,187 Da. The predicted cyaA gene product had structural similarity to the receptor-type adenylyl cyclases that are composed of an amino-terminal sensor domain and a carboxy-terminal catalytic domain of adenylyl cyclase. In reverse transcriptase PCR experiments, the transcript of the cyaA gene was detected mainly during development and spore germination. A cyaA mutant, generated by gene disruption, showed normal growth, development, and germination. However, a cyaA mutant placed under conditions of ionic (NaCl) or nonionic (sucrose) osmostress exhibited a marked reduction in spore formation and spore germination. When wild-type and cyaA mutant cells at developmental stages were stimulated with 0.2 M NaCl or sucrose, the mutant cells increased cyclic AMP accumulation at levels similar to those of the wild-type cells. In contrast, the mutant cells during spore germination had mainly lost the ability to respond to high-ionic osmolarity. In vegetative cells, the cyaA mutant responded normally to osmotic stress. These results suggested that M. xanthus CyaA functions mainly as an ionic osmosensor during spore germination and that CyaA is also required for osmotic tolerance in fruiting formation and sporulation.

scholarly journals Mutations at the suppressor of forked locus increase the accumulation of gypsy-encoded transcripts in Drosophila melanogaster.

1986 ◽  
Vol 6 (6) ◽  
pp. 2271-2274 ◽  
Author(s):  
S M Parkhurst ◽  
V G Corces
Keyword(s):  
Drosophila Melanogaster ◽  
Transposable Element ◽  
Negative Regulator ◽  
Developmental Expression ◽  
Wild Type ◽  
Stages Of Development

We studied the effect of mutations at the suppressor of forked [su(f)] locus in Drosophila melanogaster on the accumulation of transcripts encoded by the gypsy transposable element. Mutations at this locus do not affect the pattern of developmental expression of gypsy, but they cause an increase in the total amount of gypsy RNA present at different stages of development as compared with wild-type or su(f)/+ flies. These results suggest that the su(f)-encoded products acts as a negative regulator of gypsy expression.

scholarly journals SPX-related genes regulate phosphorus homeostasis in the marine phytoplankton, Phaeodactylum tricornutum

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Kaidian Zhang ◽  
Zhi Zhou ◽  
Jiashun Li ◽  
Jingtian Wang ◽  
Liying Yu ◽  
...  
Keyword(s):  
Stress Responses ◽  
Phaeodactylum Tricornutum ◽  
Response Regulator ◽  
P Uptake ◽  
Negative Regulator ◽  
Marine Phytoplankton ◽  
Alkaline Phosphatases ◽  
Phosphate Starvation Response ◽  
Essential Nutrient ◽  
Global Oceans

AbstractPhosphorus (P) is an essential nutrient for marine phytoplankton. Maintaining intracellular P homeostasis against environmental P variability is critical for phytoplankton, but how they achieve this is poorly understood. Here we identify a SPX gene and investigate its role in Phaeodactylum tricornutum. SPX knockout led to significant increases in the expression of phosphate transporters, alkaline phosphatases (the P acquisition machinery) and phospholipid hydrolases (a mechanism to reduce P demand). These demonstrate that SPX is a negative regulator of both P uptake and P-stress responses. Furthermore, we show that SPX regulation of P uptake and metabolism involves a phosphate starvation response regulator (PHR) as an intermediate. Additionally, we find the SPX related genes exist and operate across the phytoplankton phylogenetic spectrum and in the global oceans, indicating its universal importance in marine phytoplankton. This study lays a foundation for better understanding phytoplankton adaptation to P variability in the future changing oceans.

scholarly journals FixJ family regulator AcfR of Azorhizobium caulinodans is involved in symbiosis with the host plant

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Wei Liu ◽  
Xue Bai ◽  
Yan Li ◽  
Haikun Zhang ◽  
Xiaoke Hu
Keyword(s):  
Signal Transduction ◽  
Host Plant ◽  
Type Strain ◽  
Wild Type Strain ◽  
Response Regulator ◽  
Azorhizobium Caulinodans ◽  
Wild Type ◽  
Response Regulators ◽  
Free Living ◽  
Two Component

Abstract Background A wide variety of bacterial adaptative responses to environmental conditions are mediated by signal transduction pathways. Two-component signal transduction systems are one of the predominant means used by bacteria to sense the signals of the host plant and adjust their interaction behaviour. A total of seven open reading frames have been identified as putative two-component response regulators in the gram-negative nitrogen-fixing bacteria Azorhizobium caulinodans ORS571. However, the biological functions of these response regulators in the symbiotic interactions between A. caulinodans ORS571 and the host plant Sesbania rostrata have not been elucidated to date. Results In this study, we identified and investigated a two-component response regulator, AcfR, with a phosphorylatable N-terminal REC (receiver) domain and a C-terminal HTH (helix-turn-helix) LuxR DNA-binding domain in A. caulinodans ORS571. Phylogenetic analysis showed that AcfR possessed close evolutionary relationships with NarL/FixJ family regulators. In addition, six histidine kinases containing HATPase_c and HisKA domains were predicted to interact with AcfR. Furthermore, the biological function of AcfR in free-living and symbiotic conditions was elucidated by comparing the wild-type strain and the ΔacfR mutant strain. In the free-living state, the cell motility behaviour and exopolysaccharide production of the ΔacfR mutant were significantly reduced compared to those of the wild-type strain. In the symbiotic state, the ΔacfR mutant showed a competitive nodule defect on the stems and roots of the host plant, suggesting that AcfR can provide A. caulinodans with an effective competitive ability for symbiotic nodulation. Conclusions Our results showed that AcfR, as a response regulator, regulates numerous phenotypes of A. caulinodans under the free-living conditions and in symbiosis with the host plant. The results of this study help to elucidate the involvement of a REC + HTH_LuxR two-component response regulator in the Rhizobium-host plant interaction.

scholarly journals Deletion of znuA Virulence Factor Attenuates Brucella abortus and Confers Protection against Wild-Type Challenge

2006 ◽  
Vol 74 (7) ◽  
pp. 3874-3879 ◽  
Author(s):  
Xinghong Yang ◽  
Todd Becker ◽  
Nancy Walters ◽  
David W. Pascual
Keyword(s):  
Brucella Abortus ◽  
Deletion Mutant ◽  
Pasteurella Multocida ◽  
Brucella Melitensis ◽  
Normal Growth ◽  
Wild Type ◽  
Minimal Growth ◽  
M Genome ◽  
S19 Vaccine ◽  
Knockout Mutation

ABSTRACT znuA is known to be an important factor for survival and normal growth under low Zn2+ concentrations for Escherichia coli, Haemophilus spp., Neisseria gonorrhoeae, and Pasteurella multocida. We hypothesized that the znuA gene present in Brucella melitensis 16 M would be similar to znuA in B. abortus and questioned whether it may also be an important factor for growth and virulence of Brucella abortus. Using the B. melitensis 16 M genome sequence, primers were designed to construct a B. abortus deletion mutant. A znuA knockout mutation in B. abortus 2308 (ΔznuA) was constructed and found to be lethal in low-Zn2+ medium. When used to infect macrophages, ΔznuA B. abortus showed minimal growth. Further study with ΔznuA B. abortus showed that its virulence in BALB/c mice was attenuated, and most of the bacteria were cleared from the spleen within 8 weeks. Protection studies confirmed the ΔznuA mutant as a potential live vaccine, since protection against wild-type B. abortus 2308 challenge was as effective as that obtained with the RB51 or S19 vaccine strain.

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