scholarly journals PXO_RS20535, Encoding a Novel Response Regulator, Is Required for Chemotactic Motility, Biofilm Formation, and Tolerance to Oxidative Stress in Xanthomonas oryzae pv. oryzae

Pathogens ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 956
Author(s):  
Abdulwahab Antar ◽  
Mi-Ae Lee ◽  
Youngchul Yoo ◽  
Man-Ho Cho ◽  
Sang-Won Lee
Keyword(s):  
Oxidative Stress ◽  
Mutant Strain ◽  
Intracellular Signaling ◽  
Biofilm Formation ◽  
Response Regulator ◽  
Xanthomonas Oryzae ◽  
Knockout Mutant ◽  
Gene Encoding ◽  
Growth And Survival ◽  
Intracellular Signaling Pathway

Xanthomonas oryzae pv. oryzae (Xoo), a causal agent of bacterial leaf blight of rice, possesses two-component regulatory systems (TCSs) as an intracellular signaling pathway. In this study, we observed changes in virulence, biofilm formation, motility, chemotaxis, and tolerance against oxidative stress of a knockout mutant strain for the PXO_RS20535 gene, encoding an orphan response regulator (RR). The mutant strain lost virulence, produced significantly less biofilm, and showed remarkably reduced motility in swimming, swarming, and twitching. Furthermore, the mutant strain lost glucose-guided movement and showed clear diminution of growth and survival in the presence of H2O2. These results indicate that the RR protein encoded in the PXO_RS20535 gene (or a TCS mediated by the protein) is closely involved in regulation of biofilm formation, all types of motility, chemotaxis, and tolerance against reactive oxygen species (ROS) in Xoo. Moreover we found that the expression of most genes required for a type six secretion system (T6SS) was decreased in the mutant, suggesting that lack of the RR gene most likely leads to defect of T6SS in Xoo.

scholarly journals Identification of an Orphan Response Regulator Required for the Virulence of Francisella spp. and Transcription of Pathogenicity Island Genes

2007 ◽  
Vol 75 (7) ◽  
pp. 3305-3314 ◽  
Author(s):  
Nrusingh P. Mohapatra ◽  
Shilpa Soni ◽  
Brian L. Bell ◽  
Richard Warren ◽  
Robert K. Ernst ◽  
...  
Keyword(s):  
Gene Expression ◽  
Mutant Strain ◽  
Lipid A ◽  
Response Regulator ◽  
Model Organism ◽  
Virulence Gene ◽  
Pathogenicity Island ◽  
Effective Vaccine ◽  
Gene Encoding ◽  
Virulence Gene Expression

ABSTRACT Francisella tularensis is a category A agent of biowarfare/biodefense. Little is known about the regulation of virulence gene expression in Francisella spp. Comparatively few regulatory factors exist in Francisella, including those belonging to two-component systems (TCS). However, orphan members of typical TCS can be identified. To determine if orphan TCS members affect Francisella gene expression, a gene encoding a product with high similarity to the Salmonella PmrA response regulator (FTT1557c/FNU0663.2) was deleted in Francisella novicida (a model organism for F. tularensis). The F. novicida pmrA mutant was defective in survival/growth within human and murine macrophage cell lines and was 100% defective in virulence in mice at a dose of up to 108 CFU. In addition, the mutant strain demonstrated increased susceptibility to antimicrobial peptide killing, but no differences were observed between the lipid A of the mutant and the parental strain, as has been observed with pmrA mutants of other microbes. The F. novicida pmrA mutant was 100% protective as a single-dose vaccine when challenge was with 106 CFU of F. novicida but did not protect against type A Schu S4 wild-type challenge. DNA microarray analysis identified 65 genes regulated by PmrA. The majority of these genes were located in the region surrounding pmrA or within the Francisella pathogenicity island (FPI). These FPI genes are also regulated by MglA, but MglA does not regulate pmrA, nor does PmrA regulate MglA. Thus, the orphan response regulator PmrA is an important factor in controlling virulence in F. novicida, and a pmrA mutant strain is an effective vaccine against homologous challenge.

scholarly journals Functional Analysis of luxS in the Probiotic Strain Lactobacillus rhamnosus GG Reveals a Central Metabolic Role Important for Growth and Biofilm Formation

2006 ◽  
Vol 189 (3) ◽  
pp. 860-871 ◽  
Author(s):  
Sarah Lebeer ◽  
Sigrid C. J. De Keersmaecker ◽  
Tine L. A. Verhoeven ◽  
Abeer A. Fadda ◽  
Kathleen Marchal ◽  
...  
Keyword(s):  
Biofilm Formation ◽  
Lactobacillus Rhamnosus ◽  
In Silico Analysis ◽  
Probiotic Strain ◽  
Transcriptional Analysis ◽  
Knockout Mutant ◽  
Gastrointestinal Microbiota ◽  
Gene Encoding ◽  
Metabolic Role ◽  
Adaptive Processes

ABSTRACT Quorum sensing is involved in the regulation of multicellular behavior through communication via small molecules. Given the high number and diversity of the gastrointestinal microbiota, it is postulated that members of this community communicate to coordinate a variety of adaptive processes. AI-2 is suggested to be a universal bacterial signaling molecule synthesized by the LuxS enzyme, which forms an integral part of the activated methyl cycle. We have previously reported that the well-documented probiotic strain Lactobacillus rhamnosus GG, a human isolate, produces AI-2-like molecules. In this study, we identified the luxS homologue of L. rhamnosus GG. luxS seems to be located in an operon with a yxjH gene encoding a putative cobalamin-independent methionine synthase. In silico analysis revealed a methionine-specific T box in the leader sequence of the putative yxjH-luxS operon. However, transcriptional analysis showed that luxS is expressed mainly as a monocistronic transcript. Construction of a luxS knockout mutant confirmed that the luxS gene is responsible for AI-2 production in L. rhamnosus GG. However, this mutation also resulted in pleiotropic effects on the growth of this fastidious strain. Cysteine, pantothenate, folic acid, and biotin could partially complement growth, suggesting a central metabolic role for luxS in L. rhamnosus GG. Interestingly, the luxS mutant also showed a defect in monospecies biofilm formation. Experiments with chemically synthesized (S)-4,5-dihydroxy-2,3-pentanedione, coculture with the wild type, and nutritional complementation suggested that the main cause of this defect has a metabolic nature. Moreover, our data indicate that suppressor mutations are likely to occur in luxS mutants of L. rhamnosus GG. Therefore, results of luxS-related studies should be carefully interpreted.

scholarly journals The Xanthomonas oryzae pv. oryzae PhoPQ Two-Component System Is Required for AvrXA21 Activity, hrpG Expression, and Virulence

2008 ◽  
Vol 190 (6) ◽  
pp. 2183-2197 ◽  
Author(s):  
Sang-Won Lee ◽  
Kyu-Sik Jeong ◽  
Sang-Wook Han ◽  
Seung-Eun Lee ◽  
Bong-Kwan Phee ◽  
...  
Keyword(s):  
Response Regulator ◽  
Gene Knockout ◽  
Constitutive Expression ◽  
Xanthomonas Oryzae ◽  
Growth Curve Analysis ◽  
Two Component System ◽  
Gene Encoding ◽  
Component System ◽  
Knockout Strain ◽  
Two Component

ABSTRACT The rice pathogen recognition receptor, XA21, confers resistance to Xanthomonas oryzae pv. oryzae strains producing the type one system-secreted molecule, AvrXA21. X. oryzae pv. oryzae requires a regulatory two-component system (TCS) called RaxRH to regulate expression of eight rax (required for AvrXA21 activity) genes and to sense population cell density. To identify other key components in this critical regulatory circuit, we assayed proteins expressed in a raxR gene knockout strain. This survey led to the identification of the phoP gene encoding a response regulator that is up-regulated in the raxR knockout strain. Next we generated a phoP knockout strain and found it to be impaired in X. oryzae pv. oryzae virulence and no longer able to activate the response regulator HrpG (hypersensitive reaction and pathogenicity G) in response to low levels of Ca2+. The impaired virulence of the phoP knockout strain can be partially complemented by constitutive expression of hrpG, indicating that PhoP controls a key aspect of X. oryzae pv. oryzae virulence through regulation of hrpG. A gene encoding the cognate putative histidine protein kinase, phoQ, was also isolated. Growth curve analysis revealed that AvrXA21 activity is impaired in a phoQ knockout strain as reflected by enhanced growth of this strain in rice lines carrying XA21. These results suggest that the X. oryzae pv. oryzae PhoPQ TCS functions in virulence and in the production of AvrXA21 in partnership with RaxRH.

scholarly journals Characterization of a Helicobacter hepaticus putA Mutant Strain in Host Colonization and Oxidative Stress

2008 ◽  
Vol 76 (7) ◽  
pp. 3037-3044 ◽  
Author(s):  
Navasona Krishnan ◽  
Alan R. Doster ◽  
Gerald E. Duhamel ◽  
Donald F. Becker
Keyword(s):  
Oxidative Stress ◽  
Mutant Strain ◽  
Helicobacter Hepaticus ◽  
Proline Metabolism ◽  
Wild Type ◽  
Knockout Mutant ◽  
Antioxidant Genes ◽  
Host Infection ◽  
H Pylori

ABSTRACT Helicobacter hepaticus is a gram-negative, spiral-shaped microaerophilic bacterium associated with chronic intestinal infection leading to hepatitis and colonic and hepatic carcinomas in susceptible strains of mice. In the closely related human pathogen Helicobacter pylori, l-proline is a preferred respiratory substrate and is found at significantly high levels in the gastric juice of infected patients. A previous study of the proline catabolic PutA flavoenzymes from H. pylori and H. hepaticus revealed that Helicobacter PutA generates reactive oxygen species during proline oxidation by transferring electrons from reduced flavin to molecular oxygen. We further explored the preference for proline as a respiratory substrate and the potential impact of proline metabolism on the redox environment in Helicobacter species during host infection by disrupting the putA gene in H. hepaticus. The resulting putA knockout mutant strain was characterized by oxidative stress analysis and mouse infection studies. The putA mutant strain of H. hepaticus exhibited increased proline levels and resistance to oxidative stress relative to that of the wild-type strain, consistent with proline's role as an antioxidant. The significant increase in stress resistance was attributed to higher proline content, as no upregulation of antioxidant genes was observed for the putA mutant strain. The wild-type and putA mutant H. hepaticus strains displayed similar levels of infection in mice, but in mice challenged with the putA mutant strain, significantly reduced inflammation was observed, suggesting a role for proline metabolism in H. hepaticus pathogenicity in vivo.

scholarly journals BAFF-R promotes cell proliferation and survival through interaction with IKKβ and NF-κB/c-Rel in the nucleus of normal and neoplastic B-lymphoid cells

Blood ◽  
2009 ◽  
Vol 113 (19) ◽  
pp. 4627-4636 ◽  
Author(s):  
Lingchen Fu ◽  
Yen-Chiu Lin-Lee ◽  
Lan V. Pham ◽  
Archito T. Tamayo ◽  
Linda C. Yoshimura ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
B Cell ◽  
B Lymphocytes ◽  
Cell Nucleus ◽  
Intracellular Signaling ◽  
Histone H3 ◽  
Lymphoid Cells ◽  
Growth And Survival ◽  
Intracellular Signaling Pathway ◽  
Non Hodgkin Lymphoma

Abstract BLyS and its major receptor BAFF-R have been shown to be critical for development and homeostasis of normal B lymphocytes, and for cell growth and survival of neoplastic B lymphocytes, but the biologic mechanisms of this ligand/receptor-derived intracellular signaling pathway(s) have not been completely defined. We have discovered that the BAFF-R protein was present in the cell nucleus, in addition to its integral presence in the plasma membrane and cytoplasm, in both normal and neoplastic B cells. BAFF-R interacted with histone H3 and IKKβ in the cell nucleus, enhancing histone H3 phosphorylation through IKKβ. Nuclear BAFF-R was also associated with NF-κB/c-Rel and bound to NF-κB targeted promoters including BLyS, CD154, Bcl-xL, IL-8, and Bfl-1/A1, promoting the transcription of these genes. These observations suggested that in addition to activating NF-κB pathways in the plasma membrane, BAFF-R also promotes normal B-cell and B-cell non-Hodgkin lymphoma (NHL-B) survival and proliferation by functioning as a transcriptional regulator through a chromatin remodeling mechanism(s) and NF-κB association. Our studies provide an expanded conceptual view of the BAFF-R signaling, which should contribute a better understanding of the physiologic mechanisms involved in normal B-cell survival and growth, as well as in the pathophysiology of aggressive B-cell malignancies and autoimmune diseases.

scholarly journals CdpA Is a Burkholderia pseudomallei Cyclic di-GMP Phosphodiesterase Involved in Autoaggregation, Flagellum Synthesis, Motility, Biofilm Formation, Cell Invasion, and Cytotoxicity

2010 ◽  
Vol 78 (5) ◽  
pp. 1832-1840 ◽  
Author(s):  
Hwee Siang Lee ◽  
Feiyu Gu ◽  
Shi Min Ching ◽  
Yulin Lam ◽  
Kim Lee Chua
Keyword(s):  
Intracellular Signaling ◽  
Biofilm Formation ◽  
Burkholderia Pseudomallei ◽  
Cell Aggregation ◽  
Lung Epithelial Cells ◽  
Human Macrophage ◽  
Null Mutant ◽  
Gene Encoding ◽  
Fold Reduction

ABSTRACT Cyclic diguanylic acid (c-di-GMP) is an intracellular signaling molecule involved in regulation of cellular functions such as motility, biofilm formation and virulence. Intracellular level of c-di-GMP is controlled through opposing diguanylate cyclase (DGC) and phosphodiesterase (PDE) activities of GGDEF and EAL domain proteins, respectively. We report the identification and characterization of cdpA, a gene encoding a protein containing an EAL domain in the Gram-negative soil bacillus and human pathogen Burkholderia pseudomallei KHW. Purified recombinant CdpA protein exhibited PDE activity in vitro. Evidence that CdpA is a major c-di-GMP-specific PDE in B. pseudomallei KHW was shown by an 8-fold-higher c-di-GMP level in the cdpA-null mutant as compared to the wild type and the complemented cdpA mutant. The presence of higher intracellular c-di-GMP levels in the cdpA-null mutant was associated with increased production of exopolysaccharides, increased cell-to-cell aggregation, absence of flagella and swimming motility, and increased biofilm formation. The relevance of CdpA in B. pseudomallei virulence was demonstrated by a 3-fold reduction in invasion of human lung epithelial cells and a 6-fold reduction in cytotoxicity on human macrophage cells infected with the cdpA mutant.

scholarly journals Isolation and Characterization of rpoS from a Pathogenic Bacterium, Vibrio vulnificus: Role of σS in Survival of Exponential-Phase Cells under Oxidative Stress

2004 ◽  
Vol 186 (11) ◽  
pp. 3304-3312 ◽  
Author(s):  
Kyung-Je Park ◽  
Min-Jin Kang ◽  
Songhee H. Kim ◽  
Hyun-Jung Lee ◽  
Jae-Kyu Lim ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Stationary Phase ◽  
Vibrio Vulnificus ◽  
Stationary Phases ◽  
Exponential Phase ◽  
Knockout Mutant ◽  
Gene Encoding ◽  
Isolation And Characterization ◽  
Multiple Copies

ABSTRACT A gene homologous to rpoS was cloned from a fatal human pathogen, Vibrio vulnificus. The functional role of rpoS in V. vulnificus was accessed by using an rpoS knockout mutant strain. This mutant was impaired in terms of the ability to survive under oxidative stress, nutrient starvation, UV irradiation, or acidic conditions. The increased susceptibility of the V. vulnificus mutant in the exponential phase to H2O2 was attributed to the reduced activity of hydroperoxidase I (HPI). Although σS synthesis was induced and HPI activity reached the maximal level in the stationary phase, the mutant in the stationary phase showed the same susceptibility to H2O2 as the wild-type strain in the stationary phase. In addition, HPII activity, which is known to be controlled by σS in Escherichia coli, was not detectable in V. vulnificus strains under the conditions tested. The mutant in the exponential phase complemented with multiple copies of either the rpoS or katG gene of V. vulnificus recovered both resistance to H2O2 and HPI activity compared with the control strain. Expression of the katG gene encoding HPI in V. vulnificus was monitored by using a katG::luxAB transcriptional fusion. The expression of this gene was significantly reduced by deletion of σS in both the early exponential and late stationary phases. Thus, σS is necessary for increased synthesis and activity of HPI, and σS is required for exponentially growing V. vulnificus to develop the ability to survive in the presence of H2O2.

scholarly journals The Putative Hybrid Sensor Kinase SypF Coordinates Biofilm Formation in Vibrio fischeri by Acting Upstream of Two Response Regulators, SypG and VpsR

2008 ◽  
Vol 190 (14) ◽  
pp. 4941-4950 ◽  
Author(s):  
Cynthia L. Darnell ◽  
Elizabeth A. Hussa ◽  
Karen L. Visick
Keyword(s):  
Biofilm Formation ◽  
Vibrio Fischeri ◽  
Response Regulator ◽  
Cell Aggregation ◽  
Putative Hybrid ◽  
Sensor Kinase ◽  
Gene Encoding ◽  
Subsequent Work ◽  
Pellicle Formation ◽  
Dependent Cell

ABSTRACT Colonization of the Hawaiian squid Euprymna scolopes by the marine bacterium Vibrio fischeri requires the symbiosis polysaccharide (syp) gene cluster, which contributes to symbiotic initiation by promoting biofilm formation on the surface of the symbiotic organ. We previously described roles for the syp-encoded response regulator SypG and an unlinked gene encoding the sensor kinase RscS in controlling syp transcription and inducing syp-dependent cell-cell aggregation phenotypes. Here, we report the involvement of an additional syp-encoded regulator, the putative sensor kinase SypF, in promoting biofilm formation. Through the isolation of an increased activity allele, sypF1, we determined that SypF can function to induce syp transcription as well as a variety of biofilm phenotypes, including wrinkled colony formation, adherence to glass, and pellicle formation. SypF1-mediated transcription of the syp cluster was entirely dependent on SypG. However, the biofilm phenotypes were reduced, not eliminated, in the sypG mutant. These phenotypes were also reduced in a mutant deleted for sypE, another syp-encoded response regulator. However, SypF1 still induced phenotypes in a sypG sypE double mutant, suggesting that SypF1 might activate another regulator(s). Our subsequent work revealed that the residual SypF1-induced biofilm formation depended on VpsR, a putative response regulator, and cellulose biosynthesis. These data support a model in which a network of regulators and at least two polysaccharide loci contribute to biofilm formation in V. fischeri.

THE ROLE OF PHOSPHATIDYLINOSITOL-3-KINASE IN CARCINOGENESIS

2017 ◽  
Vol 63 (4) ◽  
pp. 545-556
Author(s):  
Natalya Oskina ◽  
Aleksandr Shcherbakov ◽  
Maksim Filipenko ◽  
Nikolay Kushlinskiy ◽  
L. Ovchinnikova
Keyword(s):  
Genetic Disease ◽  
Intracellular Signaling ◽  
Somatic Mutations ◽  
Pi3k Pathway ◽  
Genetic Alterations ◽  
Phosphatidylinositol 3 Kinase ◽  
Intracellular Signaling Pathway ◽  
Metabolic Activities ◽  
Carcinogenic Process

Currently it is established that cancer is a genetic disease and that somatic mutations are the initiators of the carcinogenic process. The PI3K/AKT/mTOR pathway is an important intracellular signaling pathway regulating the cell growth and metabolic activities. Aberrant activation of the PI3K pathway is commonly observed in many different cancers. In this review we analyze the genetic alterations of PI3K pathway in a variety of human malignancies and discuss their possible implications for diagnosis and therapy.

scholarly journals Glyoxalase I disruption and external carbonyl stress impair mitochondrial function in human induced pluripotent stem cells and derived neurons

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tomonori Hara ◽  
Manabu Toyoshima ◽  
Yasuko Hisano ◽  
Shabeesh Balan ◽  
Yoshimi Iwayama ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Stem Cells ◽  
Induced Pluripotent Stem Cells ◽  
Pluripotent Stem Cells ◽  
Caspase 3 ◽  
Intervention Strategy ◽  
Underlying Mechanism ◽  
Carbonyl Stress ◽  
Gene Encoding ◽  
Induced Pluripotent

AbstractCarbonyl stress, a specific form of oxidative stress, is reported to be involved in the pathophysiology of schizophrenia; however, little is known regarding the underlying mechanism. Here, we found that disruption of GLO1, the gene encoding a major catabolic enzyme scavenging the carbonyl group, increases vulnerability to external carbonyl stress, leading to abnormal phenotypes in human induced pluripotent stem cells (hiPSCs). The viability of GLO1 knockout (KO)-hiPSCs decreased and activity of caspase-3 was increased upon addition of methylglyoxal (MGO), a reactive carbonyl compound. In the GLO1 KO-hiPSC-derived neurons, MGO administration impaired neurite extension and cell migration. Further, accumulation of methylglyoxal-derived hydroimidazolone (MG-H1; a derivative of MGO)-modified proteins was detected in isolated mitochondria. Mitochondrial dysfunction, including diminished membrane potential and dampened respiratory function, was observed in the GLO1 KO-hiPSCs and derived neurons after addition of MGO and hence might be the mechanism underlying the effects of carbonyl stress. The susceptibility to MGO was partially rescued by the administration of pyridoxamine, a carbonyl scavenger. Our observations can be used for designing an intervention strategy for diseases, particularly those induced by enhanced carbonyl stress or oxidative stress.

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