scholarly journals Effector GenexopAEofXanthomonas euvesicatoria85-10 Is Part of an Operon and Encodes an E3 Ubiquitin Ligase

2018 ◽  
Vol 200 (16) ◽  
Author(s):  
Georgy Popov ◽  
Bharat Bhusan Majhi ◽  
Guido Sessa
Keyword(s):  
Ubiquitin Ligase ◽  
Type Iii Secretion ◽  
E3 Ubiquitin Ligase ◽  
E3 Ligase ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Start Codon ◽  
Content Type ◽  
Type Iii ◽  
Xanthomonas Euvesicatoria

ABSTRACTThe type III effector XopAE from theXanthomonas euvesicatoriastrain 85-10 was previously shown to inhibit plant immunity and enhance pathogen-induced disease symptoms. Evolutionary analysis of 60xopAEalleles (AEal) revealed that thexopAElocus is conserved in multipleXanthomonasspecies. The majority ofxopAEalleles (55 out of 60) comprise a single open reading frame (ORF) (xopAE), while in 5 alleles, includingAEal 37of theX. euvesicatoria85-10 strain, a frameshift splits the locus into two ORFs (hpaFand a truncatedxopAE). To test whether the second ORF ofAEal 37(xopAE85-10) is translated, we examined expression of yellow fluorescent protein (YFP) fused downstream to truncated or mutant forms of the locus inXanthomonasbacteria. YFP fluorescence was detected at maximal levels when the reporter was in proximity to an internal ribosome binding site upstream of a rare ATT start codon in thexopAE85-10ORF but was severely reduced when these elements were abolished. In agreement with the notion thatxopAE85-10is a functional gene, its protein product was translocated into plant cells by the type III secretion system, and translocation was dependent on its upstream ORF,hpaF. Homology modeling predicted that XopAE85-10contains an E3 ligase XL box domain at the C terminus, andin vitroassays demonstrated that this domain displays monoubiquitination activity. Remarkably, the XL box was essential for XopAE85-10to inhibit pathogen-associated molecular pattern (PAMP)-induced gene expression inArabidopsisprotoplasts. Together, these results indicate that thexopAE85-10gene resides in a functional operon, which utilizes the alternative start codon ATT and encodes a novel XL box E3 ligase.IMPORTANCEXanthomonasbacteria utilize a type III secretion system to cause disease in many crops. This study provides insights into the evolution, translocation, and biochemical function of the XopAE type III secreted effector, contributing to the understanding ofXanthomonas-host interactions. We establish XopAE as a core effector of sevenXanthomonasspecies and elucidate the evolution of theXanthomonas euvesicatoriaxopAElocus, which contains an operon encoding a truncated effector. Our findings indicate that this operon evolved from the split of a multidomain gene into two ORFs that conserved the original domain function. Analysis ofxopAE85-10translation provides the first evidence for translation initiation from an ATT codon inXanthomonas. Our data demonstrate that XopAE85-10is an XL box E3 ubiquitin ligase and provide insights into the structure and function of this effector family.

scholarly journals The structure of the Slrp–Trx1 complex sheds light on the autoinhibition mechanism of the type III secretion system effectors of the NEL family

2014 ◽  
Vol 464 (1) ◽  
pp. 135-144 ◽  
Author(s):  
Samira Zouhir ◽  
Joaquín Bernal-Bayard ◽  
Mar Cordero-Alba ◽  
Elena Cardenal-Muñoz ◽  
Beatriz Guimaraes ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Ubiquitin Ligase ◽  
Type Iii Secretion ◽  
E3 Ubiquitin Ligase ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Human Protein ◽  
Present Evidence ◽  
Protein Target ◽  
Type Iii

We report the crystal structure of the Salmonella effector SlrP in complex with its human protein target thioredoxin Trx1. SlrP is a E3 ubiquitin ligase from the NEL family and we present evidence for the site of ubiquitination on Trx1.

scholarly journals Genomic Inference of Recombination-Mediated Evolution in Xanthomonas euvesicatoria and X. perforans

2018 ◽  
Vol 84 (13) ◽  
pp. e00136-18 ◽  
Author(s):  
Mustafa O. Jibrin ◽  
Neha Potnis ◽  
Sujan Timilsina ◽  
Gerald V. Minsavage ◽  
Gary E. Vallad ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Resistance Breeding ◽  
Secretion System ◽  
Bacterial Spot ◽  
Bacterial Populations ◽  
Content Type ◽  
Type Iii ◽  
Xanthomonas Perforans ◽  
Xanthomonas Euvesicatoria

ABSTRACT Recombination is a major driver of evolution in bacterial populations, because it can spread and combine independently evolved beneficial mutations. Recombinant lineages of bacterial pathogens of plants are typically associated with the colonization of novel hosts and the emergence of new diseases. Here we show that recombination between evolutionarily and phenotypically distinct plant-pathogenic lineages generated recombinant lineages with unique combinations of pathogenicity and virulence factors. Xanthomonas euvesicatoria and Xanthomonas perforans are two closely related lineages causing bacterial spot disease on tomato and pepper worldwide. We sequenced the genomes of atypical strains collected from tomato in Nigeria and observed recombination in the type III secretion system and effector genes, which showed alleles from both X. euvesicatoria and X. perforans. Wider horizontal gene transfer was indicated by the fact that the lipopolysaccharide cluster of one strain was most similar to that of a distantly related Xanthomonas pathogen of barley. This strain and others have experienced extensive genomewide homologous recombination, and both species exhibited dynamic open pangenomes. Variation in effector gene repertoires within and between species must be taken into consideration when one is breeding tomatoes for disease resistance. Resistance breeding strategies that target specific effectors must consider possibly dramatic variation in bacterial spot populations across global production regions, as illustrated by the recombinant strains observed here. IMPORTANCE The pathogens that cause bacterial spot of tomato and pepper are extensively studied models of plant-microbe interactions and cause problematic disease worldwide. Atypical bacterial spot strains collected from tomato in Nigeria, and other strains from Italy, India, and Florida, showed evidence of genomewide recombination that generated genetically distinct pathogenic lineages. The strains from Nigeria and Italy were found to have a mix of type III secretion system genes from X. perforans and X. euvesicatoria, as well as effectors from Xanthomonas gardneri. These genes and effectors are important in the establishment of disease, and effectors are common targets of resistance breeding. Our findings point to global diversity in the genomes of bacterial spot pathogens, which is likely to affect the host-pathogen interaction and influence management decisions.

scholarly journals A Salmonella Virulence Factor Activates the NOD1/NOD2 Signaling Pathway

mBio ◽  
2011 ◽  
Vol 2 (6) ◽  
Author(s):  
A. Marijke Keestra ◽  
Maria G. Winter ◽  
Daisy Klein-Douwel ◽  
Mariana N. Xavier ◽  
Sebastian E. Winter ◽  
...  
Keyword(s):  
Signaling Pathway ◽  
Type Iii Secretion ◽  
Salmonella Enterica ◽  
Intestinal Inflammation ◽  
Inflammatory Responses ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Content Type ◽  
Type Iii

ABSTRACTThe invasion-associated type III secretion system (T3SS-1) ofSalmonella entericaserotype Typhimurium (S. Typhimurium) activates the transcription factor NF-κB in tissue culture cells and induces inflammatory responses in animal models through unknown mechanisms. Here we show that bacterial delivery or ectopic expression of SipA, a T3SS-1-translocated protein, led to the activation of the NOD1/NOD2 signaling pathway and consequent RIP2-mediated induction of NF-κB-dependent inflammatory responses. SipA-mediated activation of NOD1/NOD2 signaling was independent of bacterial invasionin vitrobut required an intact T3SS-1. In the mouse colitis model, SipA triggered mucosal inflammation in wild-type mice but not in NOD1/NOD2-deficient mice. These findings implicate SipA-driven activation of the NOD1/NOD2 signaling pathway as a mechanism by which the T3SS-1 induces inflammatory responsesin vitroandin vivo.IMPORTANCESalmonella entericaserotype Typhimurium (S. Typhimurium) deploys a type III secretion system (T3SS-1) to induce intestinal inflammation and benefits from the ensuing host response, which enhances growth of the pathogen in the intestinal lumen. However, the mechanisms by which the T3SS-1 triggers inflammatory responses have not been resolved. Here we show that the T3SS-1 effector protein SipA induces NF-κB activation and intestinal inflammation by activating the NOD1/NOD2 signaling pathway. These data suggest that the T3SS-1 escalates innate responses through a SipA-mediated activation of pattern recognition receptors in the host cell cytosol.

scholarly journals Genetic Analysis of the Salmonella FliE Protein That Forms the Base of the Flagellar Axial Structure

mBio ◽  
2021 ◽  
Author(s):  
Jordan J. Hendriksen ◽  
Hee Jung Lee ◽  
Alexander J. Bradshaw ◽  
Keiichi Namba ◽  
Fabienne F. V. Chevance ◽  
...  
Keyword(s):  
Self Assembly ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Adaptor Protein ◽  
Ring Structure ◽  
Secretion System ◽  
Dual Roles ◽  
Content Type ◽  
Bacterial Flagellum ◽  
Type Iii

The FliE component of the bacterial flagellum is the first protein secreted through the flagellar type III secretion system (fT3SS) that is capable of self-assembly into the growing bacterial organelle. The FliE protein plays dual roles in the assembly of the Salmonella flagellum as the final component of the flagellar type III secretion system (fT3SS) and as an adaptor protein that anchors the rod (drive shaft) of the flagellar motor to the membrane-imbedded MS-ring structure.

scholarly journals Derivatives of Plant Phenolic Compound Affect the Type III Secretion System of Pseudomonas aeruginosa via a GacS-GacA Two-Component Signal Transduction System

2011 ◽  
Vol 56 (1) ◽  
pp. 36-43 ◽  
Author(s):  
Akihiro Yamazaki ◽  
Jin Li ◽  
Quan Zeng ◽  
Devanshi Khokhani ◽  
William C. Hutchins ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Phenolic Compounds ◽  
Virulence Factors ◽  
Type Iii Secretion ◽  
Small Rnas ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Human Pathogen ◽  
Content Type ◽  
Type Iii

ABSTRACTAntibiotic therapy is the most commonly used strategy to control pathogenic infections; however, it has contributed to the generation of antibiotic-resistant bacteria. To circumvent this emerging problem, we are searching for compounds that target bacterial virulence factors rather than their viability.Pseudomonas aeruginosa, an opportunistic human pathogen, possesses a type III secretion system (T3SS) as one of the major virulence factors by which it secretes and translocates T3 effector proteins into human host cells. The fact that this human pathogen also is able to infect several plant species led us to screen a library of phenolic compounds involved in plant defense signaling and their derivatives for novel T3 inhibitors. Promoter activity screening ofexoS, which encodes a T3-secreted toxin, identified two T3 inhibitors and two T3 inducers ofP. aeruginosaPAO1. These compounds alterexoStranscription by affecting the expression levels of the regulatory small RNAs RsmY and RsmZ. These two small RNAs are known to control the activity of carbon storage regulator RsmA, which is responsible for the regulation of the key T3SS regulator ExsA. As RsmY and RsmZ are the only targets directly regulated by GacA, our results suggest that these phenolic compounds affect the expression ofexoSthrough the GacSA-RsmYZ-RsmA-ExsA regulatory pathway.

scholarly journals RNase E Promotes Expression of Type III Secretion System Genes in Pseudomonas aeruginosa

2019 ◽  
Vol 201 (22) ◽  
Author(s):  
Josh S. Sharp ◽  
Arne Rietsch ◽  
Simon L. Dove
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Host Cells ◽  
Rnase E ◽  
Content Type ◽  
Type Iii ◽  
Small Regulatory Rnas

ABSTRACT Pseudomonas aeruginosa is an important opportunistic pathogen that employs a type III secretion system (T3SS) to inject effector proteins into host cells. Using a protein depletion system, we show that the endoribonuclease RNase E positively regulates expression of the T3SS genes. We also present evidence that RNase E antagonizes the expression of genes of the type VI secretion system and limits biofilm production in P. aeruginosa. Thus, RNase E, which is thought to be the principal endoribonuclease involved in the initiation of RNA degradation in P. aeruginosa, plays a key role in controlling the production of factors involved in both acute and chronic stages of infection. Although the posttranscriptional regulator RsmA is also known to positively regulate expression of the T3SS genes, we find that RNase E does not appreciably influence the abundance of RsmA in P. aeruginosa. Moreover, we show that RNase E still exerts its effects on T3SS gene expression in cells lacking all four of the key small regulatory RNAs that function by sequestering RsmA. IMPORTANCE The type III secretion system (T3SS) is a protein complex produced by many Gram-negative pathogens. It is capable of injecting effector proteins into host cells that can manipulate cell metabolism and have toxic effects. Understanding how the T3SS is regulated is important in understanding the pathogenesis of bacteria with such systems. Here, we show that RNase E, which is typically thought of as a global regulator of RNA stability, plays a role in regulating the T3SS in Pseudomonas aeruginosa. Depleting RNase E results in the loss of T3SS gene expression as well as a concomitant increase in biofilm formation. These observations are reminiscent of the phenotypes associated with the loss of activity of the posttranscriptional regulator RsmA. However, RNase E-mediated regulation of these systems does not involve changes in the abundance of RsmA and is independent of the known small regulatory RNAs that modulate RsmA activity.

scholarly journals Control of Type III Secretion System Effector/Chaperone Ratio Fosters Pathogen Adaptation to Host-Adherent Lifestyle

mBio ◽  
2019 ◽  
Vol 10 (5) ◽  
Author(s):  
Netanel Elbaz ◽  
Yaakov Socol ◽  
Naama Katsowich ◽  
Ilan Rosenshine
Keyword(s):  
Gene Expression ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Host Cells ◽  
Host Colonization ◽  
Content Type ◽  
Type Iii ◽  
Attached State

ABSTRACT The transition from a planktonic lifestyle to a host-attached state is often critical for bacterial virulence. Upon attachment to host cells, enteropathogenic Escherichia coli (EPEC) employs a type III secretion system (T3SS) to inject into the host cells ∼20 effector proteins, including Tir. CesT, which is encoded from the same operon downstream of tir, is a Tir-bound chaperone that facilitates Tir translocation. Upon Tir translocation, the liberated CesT remains in the bacterial cytoplasm and antagonizes the posttranscriptional regulator CsrA, thus eliciting global regulation in the infecting pathogen. Importantly, tight control of the Tir/CesT ratio is vital, since an uncontrolled surge in free CesT levels may repress CsrA in an untimely manner, thus abrogating colonization. We investigated how fluctuations in Tir translation affect the regulation of this ratio. By creating mutations that cause the premature termination of Tir translation, we revealed that the untranslated tir mRNA becomes highly unstable, resulting in a rapid drop in cesT mRNA levels and, thus, CesT levels. This mechanism couples Tir and CesT levels to ensure a stable Tir/CesT ratio. Our results expose an additional level of regulation that enhances the efficacy of the initial interaction of EPEC with the host cell, providing a better understanding of the bacterial switch from the planktonic to the cell-adherent lifestyle. IMPORTANCE Host colonization by extracellular pathogens often entails the transition from a planktonic lifestyle to a host-attached state. Enteropathogenic E. coli (EPEC), a Gram-negative pathogen, attaches to the intestinal epithelium of the host and employs a type III secretion system (T3SS) to inject effector proteins into the cytoplasm of infected cells. The most abundant effector protein injected is Tir, whose translocation is dependent on the Tir-bound chaperon CesT. Upon Tir injection, the liberated CesT binds to and inhibits the posttranscriptional regulator CsrA, resulting in reprogramming of gene expression in the host-attached bacteria. Thus, adaptation to the host-attached state involves dynamic remodeling of EPEC gene expression, which is mediated by the relative levels of Tir and CesT. Fluctuating from the optimal Tir/CesT ratio results in a decrease in EPEC virulence. Here we elucidate a posttranscriptional circuit that prevents sharp variations from this ratio, thus improving host colonization.

scholarly journals EspZ of Enteropathogenic and Enterohemorrhagic Escherichia coli Regulates Type III Secretion System Protein Translocation

mBio ◽  
2012 ◽  
Vol 3 (5) ◽  
Author(s):  
Cedric N. Berger ◽  
Valerie F. Crepin ◽  
Kobi Baruch ◽  
Aurelie Mousnier ◽  
Ilan Rosenshine ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Type Iii Secretion ◽  
Protein Translocation ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Enterohemorrhagic Escherichia Coli ◽  
Host Cells ◽  
Dependent Manner ◽  
Content Type ◽  
Type Iii

ABSTRACTTranslocation of effector proteins via a type III secretion system (T3SS) is a widespread infection strategy among Gram-negative bacterial pathogens. Each pathogen translocates a particular set of effectors that subvert cell signaling in a way that suits its particular infection cycle. However, as effector unbalance might lead to cytotoxicity, the pathogens must employ mechanisms that regulate the intracellular effector concentration. We present evidence that the effector EspZ controls T3SS effector translocation from enteropathogenic (EPEC) and enterohemorrhagic (EHEC)Escherichia coli. Consistently, an EPECespZmutant is highly cytotoxic. Following ectopic expression, we found that EspZ inhibited the formation of actin pedestals as it blocked the translocation of Tir, as well as other effectors, including Map and EspF. Moreover, during infection EspZ inhibited effector translocation following superinfection. Importantly, while EspZ of EHEC O157:H7 had a universal “translocation stop” activity, EspZ of EPEC inhibited effector translocation from typical EPEC strains but not from EHEC O157:H7 or its progenitor, atypical EPEC O55:H7. We found that the N and C termini of EspZ, which contains two transmembrane domains, face the cytosolic leaflet of the plasma membrane at the site of bacterial attachment, while the extracellular loop of EspZ is responsible for its strain-specific activity. These results show that EPEC and EHEC acquired a sophisticated mechanism to regulate the effector translocation.IMPORTANCEEnteropathogenicEscherichia coli(EPEC) and enterohemorrhagicE. coli(EHEC) are important diarrheal pathogens responsible for significant morbidity and mortality in developing countries and the developed world, respectively. The virulence strategy of EPEC and EHEC revolves around a conserved type III secretion system (T3SS), which translocates bacterial proteins known as effectors directly into host cells. Previous studies have shown that when cells are infected in two waves with EPEC, the first wave inhibits effector translocation by the second wave in a T3SS-dependent manner, although the factor involved was not known. Importantly, we identified EspZ as the effector responsible for blocking protein translocation following a secondary EPEC infection. Interestingly, we found that while EspZ of EHEC can block protein translocation from both EPEC and EHEC strains, EPEC EspZ cannot block translocation from EHEC. These studies show that EPEC and EHEC employ a novel infection strategy to regulate T3SS translocation.

scholarly journals Novel Type III Effectors in Pseudomonas aeruginosa

mBio ◽  
2015 ◽  
Vol 6 (2) ◽  
Author(s):  
David Burstein ◽  
Shirley Satanower ◽  
Michal Simovitch ◽  
Yana Belnik ◽  
Meital Zehavi ◽  
...  
Keyword(s):  
Machine Learning ◽  
Pseudomonas Aeruginosa ◽  
Host Cell ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Content Type ◽  
Machine Learning Classification ◽  
Type Iii ◽  
Wide Range

ABSTRACT Pseudomonas aeruginosa is a Gram-negative, opportunistic pathogen that causes chronic and acute infections in immunocompromised patients. Most P. aeruginosa strains encode an active type III secretion system (T3SS), utilized by the bacteria to deliver effector proteins from the bacterial cell directly into the cytoplasm of the host cell. Four T3SS effectors have been discovered and extensively studied in P. aeruginosa: ExoT, ExoS, ExoU, and ExoY. This is especially intriguing in light of P. aeruginosa's ability to infect a wide range of hosts. We therefore hypothesized that additional T3SS effectors that have not yet been discovered are encoded in the genome of P. aeruginosa. Here, we applied a machine learning classification algorithm to identify novel P. aeruginosa effectors. In this approach, various types of data are integrated to differentiate effectors from the rest of the open reading frames of the bacterial genome. Due to the lack of a sufficient learning set of positive effectors, our machine learning algorithm integrated genomic information from another Pseudomonas species and utilized dozens of features accounting for various aspects of the effector coding genes and their products. Twelve top-ranking predictions were experimentally tested for T3SS-specific translocation, leading to the discovery of two novel T3SS effectors. We demonstrate that these effectors are not part of the injection structural complex and report initial efforts toward their characterization. IMPORTANCE Pseudomonas aeruginosa uses a type III secretion system (T3SS) to secrete toxic proteins, termed effectors, directly into the cytoplasm of the host cell. The activation of this secretion system is correlated with disease severity and patient death. Compared with many other T3SS-utilizing pathogenic bacteria, P. aeruginosa has a fairly limited arsenal of effectors that have been identified. This is in sharp contrast with the wide range of hosts that this bacterium can infect. The discovery of two novel effectors described here is an important step toward better understanding of the virulence and host evasion mechanisms adopted by this versatile pathogen and may provide novel approaches to treat P. aeruginosa infections.

scholarly journals A Novel Phage Element of Salmonella enterica Serovar Enteritidis P125109 Contributes to Accelerated Type III Secretion System 2-Dependent Early Inflammation Kinetics in a Mouse Colitis Model

2012 ◽  
Vol 80 (9) ◽  
pp. 3236-3246 ◽  
Author(s):  
Vikalp Vishwakarma ◽  
Balamurugan Periaswamy ◽  
Niladri Bhusan Pati ◽  
Emma Slack ◽  
Wolf-Dietrich Hardt ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
Salmonella Enterica ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Pathogenic Potential ◽  
Putative Gene ◽  
Content Type ◽  
Type Iii ◽  
Genomic Study ◽  
System 2

ABSTRACTSalmonella entericasubsp. I serovar Enteritidis exhibits type III secretion system 2 (TTSS2)-dependent early colonization and inflammation kinetics faster than those of closely relatedS. entericaserovar Typhimurium. To investigate the accelerated TTSS-2-dependent pathogenic potential ofS. Enteritidis, we focused on its genome. Results of a previously published comparative genomic study revealed the presence of mutually exclusive genes in both serovars. In this study, we investigated the roles of sixS. Enteritidis-specific genesin vivoby using differential fluorescence induction (DFI) through putative gene-specific promoters. The promoter construct associated with the gene locusSEN1140induced green fluorescent protein (GFP) expression in the gut lumen, lamina propria, mesenteric lymph nodes, and related systemic organs. To further investigate the potential role ofSEN1140, we compared aSEN1140deletion mutant withS. Typhimurium in a TTSS1-deficient background. Interestingly, theS. Enteritidis mutant lackingSEN1140did not show the unique TTSS-2-dependent early colonization and inflammation kinetic phenotype ofS. Typhimurium. Consistent with this result, complementation ofSEN1140restored the TTSS-2-dependent accelerated inflammatory potential ofS. Enteritidis. This report presents a suitable screening strategy that uses a combination of DFI, fluorescence-activated cell sorting, quantitative PCR, and wild-type isogenic tagged-strain techniques to explore the unique roles ofS. Enteritidis-specific genes in bacterial pathogenesis.

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