scholarly journals Motility control through an anti-activation mechanism in Agrobacterium tumefaciens

2021 ◽  
Author(s):  
Melene A Alakavuklar ◽  
Brynn C Heckel ◽  
Ari M Stoner ◽  
Joseph A Stembel ◽  
Clay Fuqua
Keyword(s):  
Agrobacterium Tumefaciens ◽  
Gene Activation ◽  
Activation Mechanism ◽  
Flagellar Motility ◽  
Class Iii ◽  
Two Component System ◽  
Gene Encoding ◽  
Acid Protein ◽  
Motility Regulation ◽  
Flagellar Biogenesis

Many bacteria can migrate from a free-living, planktonic state to an attached, biofilm existence. One factor regulating this transition in the facultative plant pathogen Agrobacterium tumefaciens is the ExoR-ChvG-ChvI system. Periplasmic ExoR regulates activity of the ChvG-ChvI two-component system in response to environmental stress, most notably low pH. ChvI impacts hundreds of genes, including those required for type VI secretion, virulence, biofilm formation, and flagellar motility. Previous studies revealed that activated ChvG-ChvI represses expression of most of class II and class III flagellar biogenesis genes, but not the master motility regulators visN, visR, and rem. In this study, we characterized the integration of the ExoR-ChvG-ChvI and VisNR-Rem pathways. We isolated motile suppressors of the non-motile ΔexoR mutant and thereby identified the previously unannotated mirA gene encoding a 76 amino acid protein. We report that the MirA protein interacts directly with the Rem DNA-binding domain, sequestering Rem and preventing motility gene activation. The ChvG-ChvI pathway activates mirA expression and elevated mirA is sufficient to block motility. This study reveals how the ExoR-ChvG-ChvI pathway prevents flagellar motility in A. tumefaciens. MirA is also conserved among other members of the Rhizobiales suggesting similar mechanisms of motility regulation.

scholarly journals Agrobacterium tumefaciens ExoR represses succinoglycan biosynthesis and is required for biofilm formation and motility

Microbiology ◽  
2010 ◽  
Vol 156 (9) ◽  
pp. 2670-2681 ◽  
Author(s):  
Amelia D. Tomlinson ◽  
Bronwyn Ramey-Hartung ◽  
Travis W. Day ◽  
Peter M. Merritt ◽  
Clay Fuqua
Keyword(s):  
Agrobacterium Tumefaciens ◽  
Biofilm Formation ◽  
Sinorhizobium Meliloti ◽  
Plant Tissues ◽  
Flagellar Motility ◽  
Regulatory Pathway ◽  
Flow Conditions ◽  
Two Component System ◽  
Form Complex ◽  
Abiotic Surfaces

The ubiquitous plant pathogen Agrobacterium tumefaciens attaches efficiently to plant tissues and abiotic surfaces and can form complex biofilms. A genetic screen for mutants unable to form biofilms on PVC identified disruptions in a homologue of the exoR gene. ExoR is a predicted periplasmic protein, originally identified in Sinorhizobium meliloti, but widely conserved among alphaproteobacteria. Disruptions in the A. tumefaciens exoR gene result in severely compromised attachment to abiotic surfaces under static and flow conditions, and to plant tissues. These mutants are hypermucoid due to elevated production of the exopolysaccharide succinoglycan, via derepression of the exo genes that direct succinoglycan synthesis. In addition, exoR mutants have lost flagellar motility, do not synthesize detectable flagellin and are diminished in flagellar gene expression. The attachment deficiency is, however, complex and not solely attributable to succinoglycan overproduction or motility disruption. A. tumefaciens ExoR can function independently of the ChvG–ChvI two component system, implicated in ExoR-dependent regulation in S. meliloti. Mutations that suppress the exoR motility defect suggest a branched regulatory pathway controlling succinoglycan synthesis, motility and biofilm formation.

Effects of an Autoregulatory Senescence-inhibitor Gene Construct on Nicotiana alata Link and Otto.

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 519d-519 ◽  
Author(s):  
Kenneth R. Schroeder ◽  
Dennis P. Stimart
Keyword(s):  
Agrobacterium Tumefaciens ◽  
Plant Height ◽  
Dry Weight ◽  
Nicotiana Alata ◽  
Wild Type ◽  
Gene Encoding ◽  
Delayed Senescence ◽  
Gene Construct ◽  
Shoot Dry Weight ◽  
Inhibitor System

Nicotiana alata Link and Otto. was transformed via Agrobacterium tumefaciens encoding a senescence-specific promoter SAG12 cloned from Arabidopsis thaliana fused to a Agrobacterium tumefaciens gene encoding isopentenyl transferase (IPT) that catalyzes cytokinin synthesis. This was considered an autoregulatory senescence-inhibitor system. In 1996, we reported delayed senescence of intact flowers by 2 to 6 d and delayed leaf senescence of transgenic vs. wild-type N. alata. Further evaluations in 1997 revealed several other interesting effects of the SAG12-IPT gene construct. Measurement of chlorophyll content of mature leaves showed higher levels of both chlorophyll a and b in transgenic material under normal fertilization and truncated fertilization regimes. At 4 to 5 months of age transgenic plants expressed differences in plant height, branching, and dry weight. Plant height was reduced by 3 to 13 cm; branch counts increased 2 to 3 fold; and shoot dry weight increased up to 11 g over wild-type N. alata. These observations indicate the system is not tightly autoregulated and may prove useful to the floriculture industry for producing compact and more floriferous plants.

scholarly journals The G-Protein α-Subunit GasC Plays a Major Role in Germination in the Dimorphic FungusPenicillium marneffei

Genetics ◽  
2003 ◽  
Vol 164 (2) ◽  
pp. 487-499 ◽  
Author(s):  
Sophie Zuber ◽  
Michael J Hynes ◽  
Alex Andrianopoulos
Keyword(s):  
G Protein ◽  
Germination Rate ◽  
Yeast Cells ◽  
Class Iii ◽  
Temperature Dependent ◽  
Gene Encoding ◽  
Α Subunit ◽  
G Protein Α Subunit ◽  
Opportunistic Human Pathogen

AbstractThe opportunistic human pathogen Penicillium marneffei exhibits a temperature-dependent dimorphic switch. At 25°, multinucleate, septate hyphae that can undergo differentiation to produce asexual spores (conidia) are produced. At 37° hyphae undergo arthroconidiation to produce uninucleate yeast cells that divide by fission. This work describes the cloning of the P. marneffei gasC gene encoding a G-protein α-subunit that shows high homology to members of the class III fungal Gα-subunits. Characterization of a ΔgasC mutant and strains carrying a dominant-activating gasCG45R or a dominant-interfering gasCG207R allele show that GasC is a crucial regulator of germination. A ΔgasC mutant is severely delayed in germination, whereas strains carrying a dominant-activating gasCG45R allele show a significantly accelerated germination rate. Additionally, GasC signaling positively affects the production of the red pigment by P. marneffei at 25° and negatively affects the onset of conidiation and the conidial yield, showing that GasC function overlaps with functions of the previously described Gα-subunit GasA. In contrast to the S. cerevisiae ortholog Gpa2, our data indicate that GasC is not involved in carbon or nitrogen source sensing and plays no major role in either hyphal or yeast growth or in the switch between these two forms.

scholarly journals Regulatory Role of the MisR/S Two-Component System in Hemoglobin Utilization in Neisseria meningitidis

2009 ◽  
Vol 78 (3) ◽  
pp. 1109-1122 ◽  
Author(s):  
Shuming Zhao ◽  
Grisselle E. Montanez ◽  
Pradeep Kumar ◽  
Soma Sannigrahi ◽  
Yih-Ling Tzeng
Keyword(s):  
Posttranscriptional Regulation ◽  
Regulatory Mechanisms ◽  
Two Component System ◽  
Gene Encoding ◽  
Positive Role ◽  
Upstream Gene ◽  
Component System ◽  
Two Component ◽  
Major Surface

ABSTRACT Outer membrane iron receptors are some of the major surface entities that are critical for meningococcal pathogenesis. The gene encoding the meningococcal hemoglobin receptor, HmbR, is both independently transcribed and transcriptionally linked to the upstream gene hemO, which encodes a heme oxygenase. The MisR/S two-component system was previously determined to regulate hmbR transcription, and its hemO and hmbR regulatory mechanisms were characterized further here. The expression of hemO and hmbR was downregulated in misR/S mutants under both iron-replete and iron-restricted conditions, and the downregulation could be reversed by complementation. No significant changes in expression of other iron receptors were detected, suggesting that the MisR/S system specifically regulates hmbR. When hemoglobin was the sole iron source, growth defects were detected in the mutants. Primer extension analysis identified a promoter upstream of the hemO-associated Correia element (CE) and another promoter at the proximal end of CE, and processed transcripts previously identified for other cotranscribed CEs were also detected, suggesting that there may be posttranscriptional regulation. MisR directly interacts with sequences upstream of the CE and upstream of the hmbR Fur binding site and thus independently regulates hemO and hmbR. Analysis of transcriptional reporters of hemO and hmbR further demonstrated the positive role of the MisR/S system and showed that the transcription of hmbR initiated from hemO was significantly reduced. A comparison of the effects of the misS mutation under iron-replete and iron-depleted conditions suggested that activation by the MisR/S system and iron-mediated repression by Fur act independently. Thus, the expression of hemO and hmbR is coordinately controlled by multiple independent regulatory mechanisms, including the MisR/S two-component system.

scholarly journals The Synechococcus Strain PCC 7942glnN Product (Glutamine Synthetase III) Helps Recovery from Prolonged Nitrogen Chlorosis

2000 ◽  
Vol 182 (19) ◽  
pp. 5615-5619 ◽  
Author(s):  
Jörg Sauer ◽  
Ulrike Dirmeier ◽  
Karl Forchhammer
Keyword(s):  
Glutamine Synthetase ◽  
Transcriptional Start Site ◽  
Binding Motif ◽  
Class Iii ◽  
Wild Type ◽  
Cloning And Sequencing ◽  
Gene Encoding ◽  
Low Concentrations ◽  
Synechococcus Strain ◽  
Pcc 7942

ABSTRACT We report the cloning and sequencing of the glnN gene encoding a class III glutamine synthetase from the cyanobacteriumSynechococcus strain PCC 7942. Mapping of the transcriptional start site revealed a DNA sequence in the promoter region that resembles an imperfect NtcA binding motif. Expression ofglnN is impaired in NtcA- and PII-deficient mutants. The only parameter which was negatively affected in theglnN mutant compared to the wild type was the recovery rate of prolonged nitrogen-starved cells with low concentrations of combined nitrogen.

scholarly journals IC138 Defines a Subdomain at the Base of the I1 Dynein That Regulates Microtubule Sliding and Flagellar Motility

2009 ◽  
Vol 20 (13) ◽  
pp. 3055-3063 ◽  
Author(s):  
Raqual Bower ◽  
Kristyn VanderWaal ◽  
Eileen O'Toole ◽  
Laura Fox ◽  
Catherine Perrone ◽  
...  
Keyword(s):  
Double Mutant ◽  
Essential Role ◽  
Null Allele ◽  
Flagellar Motility ◽  
Wild Type ◽  
Gene Encoding ◽  
Radial Spoke ◽  
Mutant Strains ◽  
Dynein Arms ◽  
Image Averaging

To understand the mechanisms that regulate the assembly and activity of flagellar dyneins, we focused on the I1 inner arm dynein (dynein f) and a null allele, bop5-2, defective in the gene encoding the IC138 phosphoprotein subunit. I1 dynein assembles in bop5-2 axonemes but lacks at least four subunits: IC138, IC97, LC7b, and flagellar-associated protein (FAP) 120—defining a new I1 subcomplex. Electron microscopy and image averaging revealed a defect at the base of the I1 dynein, in between radial spoke 1 and the outer dynein arms. Microtubule sliding velocities also are reduced. Transformation with wild-type IC138 restores assembly of the IC138 subcomplex and rescues microtubule sliding. These observations suggest that the IC138 subcomplex is required to coordinate I1 motor activity. To further test this hypothesis, we analyzed microtubule sliding in radial spoke and double mutant strains. The results reveal an essential role for the IC138 subcomplex in the regulation of I1 activity by the radial spoke/phosphorylation pathway.

scholarly journals The gene encoding the transcription factor SCIP has features of an expressed retroposon.

1991 ◽  
Vol 11 (9) ◽  
pp. 4642-4650 ◽  
Author(s):  
R Kuhn ◽  
E S Monuki ◽  
G Lemke
Keyword(s):  
Transcription Factor ◽  
Schwann Cells ◽  
Cpg Island ◽  
Single Copy ◽  
Gene Encoding ◽  
Intronless Gene ◽  
Gene Comparison ◽  
Acid Protein ◽  
Central Nervous Systems ◽  
Glial Progenitor Cells

SCIP is a POU domain transcription factor expressed by glial progenitor cells in the peripheral and central nervous systems (dividing Schwann cells and O-2A cells, respectively), where it appears to act as a repressor of myelin-specific genes. We have isolated genomic clones encoding the rat SCIP gene. Comparison of the structure of these clones with genomic Southern blots and SCIP cDNAs demonstrates that SCIP is encoded in a single-copy, intronless gene that has the general features of an expressed retroposon. This gene contributes to an extended CpG island. It is transcribed to produce a 3.1-kb mRNA that encodes a 451-amino-acid protein with a predicted molecular mass of 45 kDa. Immunopurified SCIP antibodies specifically recognize a nuclear protein of this size in cultured proliferating Schwann cells, and gel shift analyses demonstrate that this protein is the predominant octamer-binding protein in these cells.

scholarly journals Cell Surface Engineering of a β-Galactosidase for Galactooligosaccharide Synthesis

2009 ◽  
Vol 75 (18) ◽  
pp. 5938-5942 ◽  
Author(s):  
Yumei Li ◽  
Lili Lu ◽  
Hongmei Wang ◽  
Xiaodong Xu ◽  
Min Xiao
Keyword(s):  
Cell Surface ◽  
Surface Engineering ◽  
Yeast Cells ◽  
Penicillium Expansum ◽  
Yeast Nitrogen Base ◽  
Gene Encoding ◽  
Nitrogen Base ◽  
Reading Frame ◽  
Acid Protein ◽  
Casamino Acids

ABSTRACT A novel gene encoding transglycosylating β-galactosidase (BGase) was cloned from Penicillium expansum F3. The sequence contained a 3,036-bp open reading frame encoding a 1,011-amino-acid protein. This gene was subsequently expressed on the cell surface of Saccharomyces cerevisiae EBY-100 by galactose induction. The BGase-anchored yeast could directly utilize lactose to produce galactooligosaccharide (GOS), as well as the by-products glucose and a small quantity of galactose. The glucose was consumed by the yeast, and the galactose was used for BGase expression, thus greatly facilitating GOS synthesis. The GOS yield reached 43.64% when the recombinant yeast was cultivated in yeast nitrogen base-Casamino Acids medium containing 100 g/liter initial lactose at 25°C for 5 days. The yeast cells were harvested and recycled for the next batch of GOS synthesis. During sequential operations, both oligosaccharide synthesis and BGase expression were maintained at high levels with GOS yields of over 40%, and approximately 8 U/ml of BGase was detected in each batch.

The gene encoding the transcription factor SCIP has features of an expressed retroposon

1991 ◽  
Vol 11 (9) ◽  
pp. 4642-4650
Author(s):  
R Kuhn ◽  
E S Monuki ◽  
G Lemke
Keyword(s):  
Transcription Factor ◽  
Schwann Cells ◽  
Cpg Island ◽  
Single Copy ◽  
Gene Encoding ◽  
Intronless Gene ◽  
Gene Comparison ◽  
Acid Protein ◽  
Central Nervous Systems ◽  
Glial Progenitor Cells

SCIP is a POU domain transcription factor expressed by glial progenitor cells in the peripheral and central nervous systems (dividing Schwann cells and O-2A cells, respectively), where it appears to act as a repressor of myelin-specific genes. We have isolated genomic clones encoding the rat SCIP gene. Comparison of the structure of these clones with genomic Southern blots and SCIP cDNAs demonstrates that SCIP is encoded in a single-copy, intronless gene that has the general features of an expressed retroposon. This gene contributes to an extended CpG island. It is transcribed to produce a 3.1-kb mRNA that encodes a 451-amino-acid protein with a predicted molecular mass of 45 kDa. Immunopurified SCIP antibodies specifically recognize a nuclear protein of this size in cultured proliferating Schwann cells, and gel shift analyses demonstrate that this protein is the predominant octamer-binding protein in these cells.

scholarly journals Structural insights into the mechanism of c-di-GMP–bound YcgR regulating flagellar motility in Escherichia coli

2019 ◽  
Vol 295 (3) ◽  
pp. 808-821 ◽  
Author(s):  
Yan-Jie Hou ◽  
Wen-Si Yang ◽  
Yuan Hong ◽  
Ying Zhang ◽  
Da-Cheng Wang ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Motor Proteins ◽  
Flagellar Motor ◽  
Bacterial Survival ◽  
Flagellar Motility ◽  
Surface Attachment ◽  
Bacterial Surface ◽  
Motility Regulation ◽  
Survival And Growth ◽  
Structural Insights

The motile-sessile transition is critical for bacterial survival and growth. Cyclic-di-GMP (c-di-GMP) plays a central role in controlling this transition and regulating biofilm formation via various effectors. As an effector of c-di-GMP in Escherichia coli and related species, the PilZ domain–containing protein YcgR responds to elevated c-di-GMP concentrations and acts on the flagellar motor to suppress bacterial motility in a brakelike fashion, which promotes bacterial surface attachment. To date, several target proteins within the motor, MotA, FliG, and FliM, along with different regulatory mechanisms have been reported. However, how YcgR acts on these components remains unclear. Here, we report that activated YcgR stably binds to MotA at the MotA-FliG interface and thereby regulates bacterial swimming. Biochemical and structural analyses revealed that c-di-GMP rearranges the PilZ domain configuration, resulting in the formation of a MotA-binding patch consisting of an RXXXR motif and the C-tail helix α3. Moreover, we noted that a conserved region in the YcgR-N domain, which is independent of MotA interaction, is necessary for motility regulation. On the basis of these findings, we infer that the YcgR-N domain is required for activity on other motor proteins. We propose that activated YcgR appends to MotA via its PilZ domain and thereby interrupts the MotA-FliG interaction and simultaneously interacts with other motor proteins via its YcgR-N domain to inhibit flagellar motility. Our findings suggest that the mode of interaction between YcgR and motor proteins may be shared by other PilZ family proteins.

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