scholarly journals Harpin Mediates Cell Aggregation in Erwinia chrysanthemi 3937

2006 ◽  
Vol 188 (6) ◽  
pp. 2280-2284 ◽  
Author(s):  
Yap Mee-Ngan ◽  
Clemencia M. Rojas ◽  
Ching-Hong Yang ◽  
Amy O. Charkowski
Keyword(s):  
Cell Surface ◽  
Hypersensitive Response ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Cell Aggregation ◽  
Soft Rot ◽  
Secretion System ◽  
Erwinia Chrysanthemi ◽  
Type Iii

ABSTRACT The hypersensitive response elicitor harpin (HrpN) of soft rot pathogen Erwinia chrysanthemi strains 3937 and EC16 is secreted via the type III secretion system and remains cell surface bound. Strain 3937 HrpN is essential for cell aggregation, but the C-terminal one-third of the protein is not required for aggregative activity.

scholarly journals Identification of Pseudomonas syringae pv. syringae 61 Type III Secretion System Hrp Proteins That Can Travel the Type III Pathway and Contribute to the Translocation of Effector Proteins into Plant Cells

2007 ◽  
Vol 189 (15) ◽  
pp. 5773-5778 ◽  
Author(s):  
Adela R. Ramos ◽  
Joanne E. Morello ◽  
Sandeep Ravindran ◽  
Wen-Ling Deng ◽  
Hsiou-Chen Huang ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Hypersensitive Response ◽  
Type Iii Secretion ◽  
Plant Cells ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Type Iii

ABSTRACT Pseudomonas syringae translocates effector proteins into plant cells via an Hrp1 type III secretion system (T3SS). T3SS components HrpB, HrpD, HrpF, and HrpP were shown to be pathway substrates and to contribute to elicitation of the plant hypersensitive response and to translocation and secretion of the model effector AvrPto1.

scholarly journals YscP and YscU Regulate Substrate Specificity of the Yersinia Type III Secretion System

2003 ◽  
Vol 185 (7) ◽  
pp. 2259-2266 ◽  
Author(s):  
Petra J. Edqvist ◽  
Jan Olsson ◽  
Moa Lavander ◽  
Lena Sundberg ◽  
Åke Forsberg ◽  
...  
Keyword(s):  
Cell Surface ◽  
Substrate Specificity ◽  
Type Iii Secretion ◽  
Bacterial Cell ◽  
Type Iii Secretion System ◽  
Eukaryotic Cell ◽  
Secretion System ◽  
Cell Contact ◽  
Type Iii ◽  
Bacterial Cell Surface

ABSTRACT Pathogenic Yersinia species use a type III secretion system to inhibit phagocytosis by eukaryotic cells. At 37°C, the secretion system is assembled, forming a needle-like structure on the bacterial cell surface. Upon eukaryotic cell contact, six effector proteins, called Yops, are translocated into the eukaryotic cell cytosol. Here, we show that a yscP mutant exports an increased amount of the needle component YscF to the bacterial cell surface but is unable to efficiently secrete effector Yops. Mutations in the cytoplasmic domain of the inner membrane protein YscU suppress the yscP phenotype by reducing the level of YscF secretion and increasing the level of Yop secretion. These results suggest that YscP and YscU coordinately regulate the substrate specificity of the Yersinia type III secretion system. Furthermore, we show that YscP and YscU act upstream of the cell contact sensor YopN as well as the inner gatekeeper LcrG in the pathway of substrate export regulation. These results further strengthen the strong evolutionary link between flagellar biosynthesis and type III synthesis.

scholarly journals Positive Regulation of the Hrp Type III Secretion System in Pseudomonas syringae pv. phaseolicola

2010 ◽  
Vol 23 (5) ◽  
pp. 665-681 ◽  
Author(s):  
Inmaculada Ortiz-Martín ◽  
Richard Thwaites ◽  
Alberto P. Macho ◽  
John W. Mansfield ◽  
Carmen R. Beuzón
Keyword(s):  
Gene Expression ◽  
Pseudomonas Syringae ◽  
Hypersensitive Response ◽  
Type Iii Secretion ◽  
Pathogenic Bacteria ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Virulence Determinants ◽  
Type Iii

Disease in compatible hosts and induction of the hypersensitive response in resistant plants by most plant-pathogenic bacteria require a functional type III secretion system (T3SS). Expression of T3SS genes responds to host and environmental factors and is induced within the plant. In Pseudomonas syringae, expression of the T3SS requires HrpL, which is transcriptionally upregulated by HrpR and HrpS. In some pathovars, expression of the hrpRS genes is upregulated by the GacA/S two-component system. Additionally, HrpA, the major component of the T3SS pilus, has also been linked to the regulation of the hrpRS gene expression. Previous studies concerning regulation of hypersensitive response and pathogenesis/hypersensitive response conserved (hrp/hrc) gene expression have used mostly in vitro inducing conditions, different pathovars, and methodology. Here, we analyze the roles of HrpL, GacA, and HrpA in the bean pathogen, using single, double, and triple mutants as well as strains ectopically expressing the regulators. We use real-time polymerase chain reaction analysis in vitro and in planta to quantify gene expression and competitive indices and other assays to assess bacterial fitness. Our results indicate that i) HrpL acts as a general virulence regulator that upregulates non-T3SS virulence determinants and downregulates flagellar function; ii) GacA modulates the expression of hrpL, and its contribution to virulence is entirely HrpL dependent; iii) there is a basal HrpL-independent expression of the T3SS genes in rich medium that is important for full activation of the system, maybe by keeping the system primed for rapid activation upon contact with the plant; and iv) HrpA upregulates expression of the T3SS genes and is essential to activate expression of the hrpZ operon upon contact with the plant.

scholarly journals Analysis of Erwinia chrysanthemi EC16 pelE∷uidA, pelL∷uidA, and hrpN∷uidA Mutants Reveals Strain-Specific Atypical Regulation of the Hrp Type III Secretion System

2004 ◽  
Vol 17 (2) ◽  
pp. 184-194 ◽  
Author(s):  
Jong Hyun Ham ◽  
Yaya Cui ◽  
James R. Alfano ◽  
Pablo Rodríguez-Palenzuela ◽  
Clemencia M. Rojas ◽  
...  
Keyword(s):  
Growth Phase ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Medium Composition ◽  
Erwinia Chrysanthemi ◽  
Type Ii ◽  
Logarithmic Growth Phase ◽  
Direct Production ◽  
Type Iii

The plant pathogen Erwinia chrysanthemi produces a variety of factors that have been implicated in its ability to cause soft-rot diseases in various hosts. These include HrpN, a harpin secreted by the Hrp type III secretion system; PelE, one of several major pectate lyase isozymes secreted by the type II system; and PelL, one of several secondary Pels secreted by the type II system. We investigated these factors in E. chrysanthemi EC16 with respect to the effects of medium composition and growth phase on gene expression (as determined with uidA fusions and Northern analyses) and effects on virulence. pelE was induced by polygalacturonic acid, but pelL was not, and hrpN was expressed unexpectedly in nutrient-rich King's medium B and in minimal salts medium at neutral pH. In contrast, the effect of medium composition on hrp expression in E. chrysanthemi CUCPB1237 and 3937 was like that of many other phytopathogenic bacteria in being repressed in complex media and induced in acidic pH minimal medium. Northern blot analysis of hrpN and hrpL expression by the wild-type and hrpL∷ΩCmr and hrpS∷ΩCmr mutants revealed that hrpN expression was dependent on the HrpL alternative sigma factor, whose expression, in turn, was dependent on the HrpS putative σ54 enhancer binding protein. The expression of pelE and hrpN increased strongly in late logarithmic growth phase. To test the possible role of quorum sensing in this expression pattern, the expI/expR locus was cloned in Escherichia coli on the basis of its ability to direct production of acyl-homoserine lactone and then used to construct expI mutations in pelE∷uidA, pelL∷uidA, and hrpN∷uidA Erwinia chrysanthemi strains. Mutation of expI had no apparent effect on the growth-phase-dependent expression of hrpN and pelE, or on the virulence of E. chrysanthemi in witloof chicory leaves. Overexpression of hrpN in E. chrysanthemi resulted in approximately 50% reduction of lesion size on chicory leaves without an effect on infection initiation.

scholarly journals HrcT Is a Key Component of the Type III Secretion System in Xanthomonas spp. and Also Regulates the Expression of the KeyhrpTranscriptional Activator HrpX

2014 ◽  
Vol 80 (13) ◽  
pp. 3908-3919 ◽  
Author(s):  
Zhi-Yang Liu ◽  
Li-Fang Zou ◽  
Xiao-Bo Xue ◽  
Lu-Lu Cai ◽  
Wen-Xiu Ma ◽  
...  
Keyword(s):  
Hypersensitive Response ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Regulatory Proteins ◽  
Gene Products ◽  
Phytopathogenic Bacteria ◽  
Content Type ◽  
Regulatory Interactions ◽  
Type Iii

ABSTRACTThe type III secretion system (T3SS), encoded byhrp(hypersensitive response and pathogenicity) genes in Gram-negative phytopathogenic bacteria, delivers repertoires of T3SS effectors (T3SEs) into plant cells to trigger the hypersensitive response (HR) in nonhost or resistant-host plants and promote pathogenicity in susceptible plants. The expression ofhrpgenes inXanthomonasis regulated by two key regulatory proteins, HrpG and HrpX. However, the interactions betweenhrpgene products in directing T3SE secretion are largely unknown. Here we demonstrated that HrcT ofX. oryzaepv. oryzicola functions as a T3SS component and positively regulates the expression ofhrpX. Transcription ofhrcToccurs via two distinct promoters; one (T1) is with thehrpBoperon and the second (T3) withinhrpB7Via either promoter T1 or T3, the defect in Hrp phenotype byhrcTdeletion was corrected in the presence ofhrcTonly fromXanthomonasspecies but not from other phytopathogenic bacteria. An N-terminally truncated HrcT was able to bind thehrpXpromoter and activate the expression ofhrpX, supporting that HrcT is a positive regulator ofhrpX. A revised model showing the regulatory interactions between HrcT, HrpX, and HrpG is proposed.

scholarly journals The Erwinia chrysanthemi EC16 hrp/hrc Gene Cluster Encodes an Active Hrp Type III Secretion System That Is Flanked by Virulence Genes Functionally Unrelated to the Hrp System

2004 ◽  
Vol 17 (6) ◽  
pp. 644-653 ◽  
Author(s):  
Clemencia M. Rojas ◽  
Jong Hyun Ham ◽  
Lisa M. Schechter ◽  
Jihyun F. Kim ◽  
Steven V. Beer ◽  
...  
Keyword(s):  
Gene Cluster ◽  
Pseudomonas Syringae ◽  
Virulence Factors ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Gene Clusters ◽  
Amino Acid Identity ◽  
Secretion System ◽  
Erwinia Chrysanthemi ◽  
Type Iii

Erwinia chrysanthemi is a host-promiscuous plant pathogen that possesses a type III secretion system (TTSS) similar to that of the host-specific pathogens E. amylovora and Pseudomonas syringae. The regions flanking the TTSS-encoding hrp/hrc gene clusters in the latter pathogens encode various TTSS-secreted proteins. DNA sequencing of the complete E. chrysanthemi hrp/hrc gene cluster and approximately 12 kb of the flanking regions (beyond the previously characterized hecA adhesin gene in the left flank) revealed that the E. chrysanthemi TTSS genes were syntenic and similar (>50% amino-acid identity) with their E. amylovora orthologs. However, the hrp/hrc cluster was interrupted by a cluster of four genes, only one of which, a homolog of lytic transglycosylases, is implicated in TTSS functions. Furthermore, the regions flanking the hrp/hrc cluster lacked genes that were likely to encode TTSS substrates. Instead, some of the genes in these regions predict ABC transporters and methyl-accepting chemotaxis proteins that could have alternative roles in virulence. Mutations affecting all of the genes in the regions flanking or interrupting the hrp/hrc cluster were constructed in E. chrysanthemi CUCPB5047, a mutant whose reduced pectolytic capacity can enhance the phenotype of minor virulence factors. Mutants were screened in witloof chicory leaves and then in potato tubers and Nicotiana clevelandii seedlings. Mu dII1734 insertion in one gene, designated virA, resulted in strongly reduced virulence in all three tests. virA is immediately downstream of hecA, has an unusually low G+C content of 38%, and predicts an unknown protein of 111 amino acids. The E. chrysanthemi TTSS was shown to be active by its ability to translocate AvrPto-Cya (a P. syringae TTSS effector fused to an adenylate cyclase reporter that is active in the presence of eukaryote calmodulin) into N. benthamiana However, VirA(1–61)¯ Cya was not translocated into plant cells, and virA expression was not affected by mutations in E. chrysanthemi Hrp regulator genes hrpL and hrpS. Thus, the 44-kb region of the E. chrysanthemi EC16 genome that is centered on the hrp/hrc cluster encodes a potpourri of virulence factors, but none of these appear to be a TTSS effector.

scholarly journals Pseudomonas syringae Lytic Transglycosylases Coregulated with the Type III Secretion System Contribute to the Translocation of Effector Proteins into Plant Cells

2007 ◽  
Vol 189 (22) ◽  
pp. 8277-8289 ◽  
Author(s):  
Hye-Sook Oh ◽  
Brian H. Kvitko ◽  
Joanne E. Morello ◽  
Alan Collmer
Keyword(s):  
Pseudomonas Syringae ◽  
Hypersensitive Response ◽  
Type Iii Secretion ◽  
Plant Cells ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Dominant Negative Effect ◽  
Lytic Transglycosylases ◽  
Type Iii

ABSTRACT Pseudomonas syringae translocates virulence effector proteins into plant cells via a type III secretion system (T3SS) encoded by hrp (for hypersensitive response and pathogenicity) genes. Three genes coregulated with the Hrp T3SS system in P. syringae pv. tomato DC3000 have predicted lytic transglycosylase domains: PSPTO1378 (here designated hrpH), PSPTO2678 (hopP1), and PSPTO852 (hopAJ1). hrpH is located between hrpR and avrE1 in the Hrp pathogenicity island and is carried in the functional cluster of P. syringae pv. syringae 61 hrp genes cloned in cosmid pHIR11. Strong expression of DC3000 hrpH in Escherichia coli inhibits bacterial growth unless the predicted catalytic glutamate at position 148 is mutated. Translocation tests involving C-terminal fusions with a Cya (Bordetella pertussis adenylate cyclase) reporter indicate that HrpH and HopP1, but not HopAJ1, are T3SS substrates. Pseudomonas fluorescens carrying a pHIR11 derivative lacking hrpH is poorly able to translocate effector HopA1, and this deficiency can be restored by HopP1 and HopAJ1, but not by HrpH(E148A) or HrpH1-241. DC3000 mutants lacking hrpH or hrpH, hopP1, and hopAJ1 combined are variously reduced in effector translocation, elicitation of the hypersensitive response, and virulence. However, the mutants are not reduced in secretion of T3SS substrates in culture. When produced in wild-type DC3000, the HrpH(E148A) and HrpH1-241 variants have a dominant-negative effect on the ability of DC3000 to elicit the hypersensitive response in nonhost tobacco and to grow and cause disease in host tomato. The three Hrp-associated lytic transglycosylases in DC3000 appear to have overlapping functions in contributing to T3SS functions during infection.

scholarly journals Pseudomonas syringae Exchangeable Effector Loci: Sequence Diversity in Representative Pathovars and Virulence Function in P. syringae pv. syringae B728a

2003 ◽  
Vol 185 (8) ◽  
pp. 2592-2602 ◽  
Author(s):  
Wen-Ling Deng ◽  
Amos H. Rehm ◽  
Amy O. Charkowski ◽  
Clemencia M. Rojas ◽  
Alan Collmer
Keyword(s):  
Pseudomonas Syringae ◽  
Hypersensitive Response ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Brown Spot ◽  
Dependent Manner ◽  
Type Iii ◽  
Effector Genes

ABSTRACT Pseudomonas syringae is a plant pathogen whose pathogenicity and host specificity are thought to be determined by Hop/Avr effector proteins injected into plant cells by a type III secretion system. P. syringae pv. syringae B728a, which causes brown spot of bean, is a particularly well-studied strain. The type III secretion system in P. syringae is encoded by hrp (hypersensitive response and pathogenicity) and hrc (hrp conserved) genes, which are clustered in a pathogenicity island with a tripartite structure such that the hrp/hrc genes are flanked by a conserved effector locus and an exchangeable effector locus (EEL). The EELs of P. syringae pv. syringae B728a, P. syringae strain 61, and P. syringae pv. tomato DC3000 differ in size and effector gene composition; the EEL of P. syringae pv. syringae B728a is the largest and most complex. The three putative effector proteins encoded by the P. syringae pv. syringae B728a EEL—HopPsyC, HopPsyE, and HopPsyV—were demonstrated to be secreted in an Hrp-dependent manner in culture. Heterologous expression of hopPsyC, hopPsyE, and hopPsyV in P. syringae pv. tabaci induced the hypersensitive response in tobacco leaves, demonstrating avirulence activity in a nonhost plant. Deletion of the P. syringae pv. syringae B728a EEL strongly reduced virulence in host bean leaves. EELs from nine additional strains representing nine P. syringae pathovars were isolated and sequenced. Homologs of avrPphE (e.g., hopPsyE) and hopPsyA were particularly common. Comparative analyses of these effector genes and hrpK (which flanks the EEL) suggest that the EEL effector genes were acquired by horizontal transfer after the acquisition of the hrp/hrc gene cluster but before the divergence of modern pathovars and that some EELs underwent transpositions yielding effector exchanges or point mutations producing effector pseudogenes after their acquisition.

scholarly journals SlyA Regulates Type III Secretion System (T3SS) Genes in Parallel with the T3SS Master Regulator HrpL in Dickeya dadantii 3937

2012 ◽  
Vol 78 (8) ◽  
pp. 2888-2895 ◽  
Author(s):  
Lifang Zou ◽  
Quan Zeng ◽  
Haiping Lin ◽  
Prasad Gyaneshwar ◽  
Gongyou Chen ◽  
...  
Keyword(s):  
Hypersensitive Response ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Pectobacterium Carotovorum ◽  
Master Regulator ◽  
Pellicle Formation ◽  
Dickeya Dadantii ◽  
Content Type ◽  
Type Iii

ABSTRACTThe hypersensitive response and pathogenicity (hrp) genes ofDickeya dadantii3937 encode a type III secretion system (T3SS) which is essential for its full virulence. Previous studies of the T3SS regulation inD. dadantii3937 revealed that the expression of thehrpgenes is regulated by a master regulator, HrpL, through the HrpX-HrpY-HrpS-HrpL and GacS-GacA-rsmB-RsmA pathways. In this work, we identified a novel regulator of the SlyA/MarR family, SlyA, which regulateshrpgenes of the HrpL regulon in parallel with HrpL inD. dadantii. SlyA regulates the T3SS in a two-tier manner. It negatively regulates the expression ofhrpLby downregulatinghrpSand upregulatingrsmA. Interestingly, concomitant with its downregulation of thehrpL, SlyA positively regulates the expression ofhrpAandhrpN, twohrpgenes located in the HrpL regulon. In contrast toPectobacterium carotovorum, the expression ofslyAis not controlled by ExpR and ExpI inD. dadantii3937. We further show that SlyA is involved in controlling swimming motility and pellicle formation inD. dadantii3937.

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