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  • 1
    Electronic Resource
    Electronic Resource
    TYPE III SECRETION SYSTEM EFFECTOR PROTEINS: Double Agents in Bacterial Disease and Plant Defense (2004)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Phytopathology 42 (2004), S. 385-414 
    Details
    ISSN: 0066-4286
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Biology
    Notes: Many phytopathogenic bacteria inject virulence effector proteins into plant cells via a Hrp type III secretion system (TTSS). Without the TTSS, these pathogens cannot defeat basal defenses, grow in plants, produce disease lesions in hosts, or elicit the hypersensitive response (HR) in nonhosts. Pathogen genome projects employing bioinformatic methods to identify TTSS Hrp regulon promoters and TTSS pathway targeting signals suggest that phytopathogenic Pseudomonas, Xanthomonas, and Ralstonia spp. harbor large arsenals of effectors. The Hrp TTSS employs customized cytoplasmic chaperones, conserved export components in the bacterial envelope (also used by the TTSS of animal pathogens), and a more specialized set of TTSS-secreted proteins to deliver effectors across the plant cell wall and plasma membrane. Many effectors can act as molecular double agents that betray the pathogen to plant defenses in some interactions and suppress host defenses in others. Investigations of the functions of effectors within plant cells have demonstrated the plasma membrane and nucleus as subcellular sites for several effectors, revealed some effectors to possess cysteine protease or protein tyrosine phosphatase activity, and provided new clues to the coevolution of bacterium-plant interactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.phyto.42.040103.110731
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  • 2
    Electronic Resource
    Electronic Resource
    The ShcA protein is a molecular chaperone that assists in the secretion of the HopPsyA effector from the type III (Hrp) protein secretion system of Pseudomonas syringae (2002)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 44 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Pseudomonas syringae uses a type III protein secretion system encoded by the Hrp pathogenicity island (Pai) to translocate effector proteins into plant cells. One of these effector proteins is HopPsyA. A small open reading frame (ORF), named shcA, precedes the hopPsyA gene in the Hrp Pai of P. s. syringae 61. The predicted amino acid sequence of shcA shares general characteristics with chaperones used in type III protein secretion systems of animal pathogens. A functionally non-polar deletion of shcA in P. s. syringae 61 resulted in the loss of detectable HopPsyA in supernatant fractions, consistent with ShcA acting as a chaperone for HopPsyA. Cosmid pHIR11 carries a functional set of type III genes from P. s. syringae 61 and confers upon saprophytes the ability to secrete HopPsyA in culture and to elicit a HopPsyA-dependent hypersensitive response (HR) on tobacco. P. fluorescens carrying a pHIR11 derivative lacking shcA failed to secrete HopPsyA in culture, but maintained the ability to secrete another type III-secreted protein, HrpZ. This pHIR11 derivative was also greatly reduced in its ability to elicit an HR, indicating that the ability to translocate HopPsyA into plant cells was compromised. Using affinity chromatography, we showed that ShcA binds directly to HopPsyA and that the ShcA binding site must reside within the first 166 amino acids of HopPsyA. Thus, ShcA represents the first demonstrated chaperone used in a type III secretion system of a bacterial plant pathogen. We searched known P. syringae type III-related genes for neighbouring ORFs that shared the general characteristics of type III chaperones and identified five additional candidate type III chaperones. Therefore, it is likely that chaperones are as prevalent in bacterial plant pathogen type III systems as they are in their animal pathogenic counterparts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.02979.x
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  • 3
    Electronic Resource
    Electronic Resource
    Analysis of the role of the Pseudomonas syringae pv. syringae HrpZ harpin in elicitation of the hypersensitive response in tobacco using functionally non-polar hrpZ deletion mutations, truncated HrpZ fragments, and hrmA mutations (1996)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 19 (1996), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Pseudomonas syringae pv. syringae, like many plant pathogenic bacteria, secretes a ‘harpin’ protein that can elicit the hypersensitive response (HR), a defensive cellular suicide, in non-host plants. The harpin-encoding hrpZ gene is located in an operon that also encodes Hrp secretion pathway components and is part of the functional cluster of hrp genes carried on cosmid pHIR11 that enables saprophytic bacteria like Escherichia coli and Pseudomonas fluorescens to elicit the HR in tobacco leaves. We have constructed functionally non-polar hrpZ deletion mutations, revealing that HrpZ is necessary for saprophytic bacteria carrying pHIR11 to elicit a typical HR, whereas it only enhances the elicitation activity of P. s. syringae. Partial deletion mutations revealed that the N-terminal 153 amino acids of HrpZ can enable E. coli MC4100-(pHIR11) to elicit a strong HR. hrpZ subclone products comprising the N-terminal 109 amino acids and C-terminal 216 amino acids, respectively, of the 341 amino acid protein were isolated and found to elicit the HR. P. fluorescens (pHIR11 hrmA ::TnphoA) mutants do not elicit the HR, but cell fractionation and immunoblot analysis revealed that they produce and secrete wild-type levels of HrpZ. Therefore, elicitor activity resides in multiple regions of HrpZ, P. syringae produces elicitor(s) in addition to HrpZ, and HrpZ is essential but not sufficient for HR elicitation by saprophytic bacteria carrying pHIR11.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1996.415946.x
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  • 4
    Electronic Resource
    Electronic Resource
    The Pseudomonas syringae type III-secreted protein HopPtoD2 possesses protein tyrosine phosphatase activity and suppresses programmed cell death in plants (2003)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 49 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The bacterial plant pathogen Pseudomonas syringae possesses a type III protein secretion system that delivers many virulence proteins into plant cells. A subset of these proteins (called Avr proteins) is recognized by the plant's innate immune system and triggers defences. One defence-associated response is the hypersensitive response (HR), a programmed cell death (PCD) of plant tissue. We have previously identified HopPtoD2 as a type III secreted protein from P. s. pv. tomato DC3000. Sequence analysis revealed that an N-terminal domain shared homology with AvrPphD and a C-terminal domain was similar to protein tyrosine phosphatases (PTPs). We demonstrated that purified HopPtoD2 possessed PTP activity and this activity required a conserved catalytic Cys residue (Cys378). Interestingly, HopPtoD2 was capable of suppressing the HR elicited by an avirulent P. syringae strain on Nicotiana benthamiana. HopPtoD2 derivatives that lacked Cys378 no longer suppressed the HR indicating that HR suppression required PTP activity. A constitutively active MAPK kinase, called NtMEK2DD, is capable of eliciting an HR-like cell death when transiently expressed in tobacco. When NtMEK2DD and HopPtoD2 were co-delivered into plant cells, the HR was suppressed indicating that HopPtoD2 acts downstream of NtMEK2DD. DC3000 hopPtoD2 mutants were slightly reduced in their ability to multiply in planta and displayed an enhanced ability to elicit an HR. The identification of HopPtoD2 as a PTP and a PCD suppressor suggests that the inactivation of MAPK pathways is a virulence strategy utilized by bacterial plant pathogens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03588.x
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  • 5
    Electronic Resource
    Electronic Resource
    A type III effector ADP-ribosylates RNA-binding proteins and quells plant immunity (2007)
    [s.l.] : Nature Publishing Group
    Nature 447 (2007), S. 284-288 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The bacterial plant pathogen Pseudomonas syringae injects effector proteins into host cells through a type III protein secretion system to cause disease. The enzymatic activities of most of P. syringae effectors and their targets remain obscure. Here we show that the type III effector HopU1 is a ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature05737
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