The type III (Hrp) secretion pathway of plant pathogenic bacteria: trafficking harpins, Avr proteins, and death

Alfano, James R.; Collmer, Alan

doi:10.1128/jb.179.18.5655-5662.1997

Cited by 483 publications

(438 citation statements)

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“…Recent evidence that Avr proteins are introduced into plant cells via a type I11 secretion system, similar to that responsible for the introduction of virulence proteins into animal cells, indicates that virulence and avirulence may be host-specific aspects of the same gene (Alfano & Collmer, 1997;. Whilst markerexchange mutagenesis of avrPpiA in races 2 and 7 of Ppi did not affect pathogenicity towards the susceptible host as indicated by symptom development and bacterial growth in pea , a plasmid-borne homologue of aurPpiA2, avrRpm2, present in P. syringae pv.…”

Section: Discussionmentioning

confidence: 99%

A dispensable region of the chromosome which is associated with an avirulence gene in Pseudomonas syringae pv. pisi

Arnold

Brown²,

Jackson³

et al. 1999

Microbiology

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Lane, Bristol 8516 IQY, UK Pseudomonas syringae pv. pisi comprises a number of races which fall into two phylogenetically distinct groups (designated I and 11). Races are based on cultivar specificity in the host plant, pea (Pisum sativum), and are specified by the presence of avirulence genes. The avirulence gene avrPpiAl is present on the chromosome of all strains examined in race 2, which belongs to phylogenetic group II. A race 4B strain, from phylogenetic group I , lacks this avirulence gene and a comparative study was made of the chromosome in strains representing these two races. A race 2 cosmid clone (pAV270) carrying avrPpiA1 was used as a basis for collinearity analysis of races 2 and 4B. A region of the chromosome amounting to 8 5 kb and including avrPpiA1 was absent from race 46 compared with race 2. A fragment spanning the junction of the discontinuity in race 4B was isolated, cloned and used to delimit the extent of the additional DNA present in race 2. In both races the borders of the discontinuity contained DNA sequences which showed a high degree of conservation. A 7 bp slightly imperfect direct repeat (CCAGCT/,T) flanked the additional DNA in race 2, with a single copy in race 46. The region flanking the additional DNA was present in all races of P. syringae pv. phi. These results confirm the phylogenetic groupings in P. syringae pv. pisi.

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Section: Discussionmentioning

confidence: 99%

A dispensable region of the chromosome which is associated with an avirulence gene in Pseudomonas syringae pv. pisi

Arnold

Brown²,

Jackson³

et al. 1999

Microbiology

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“…It may differ from the pathway(s) used by externally sensed elicitors because avr gene products are injected into the plant cell through a bacterial type III secretion system (Alfano and Collmer, 1997;Mudgett and Staskawicz, 1998), obviating the need for transmembrane signaling. Significant sustained increases in intracellular calcium were found during HR caused by AvrB or AvrRpm1 in a study of transformed Arabidopsis expressing the Ca 21 -sensitive luminescent protein aequorin (Grant et al, 2000).…”

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Electrophysiological Characterization of the Arabidopsis avrRpt2-Specific Hypersensitive Response in the Absence of Other Bacterial Signals

2005

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The hypersensitive response (HR) is defined as rapid cell collapse at the infection site and often accompanies plant resistance. The physiological processes leading to HR are not well understood. Here, we report an electrophysiological characterization of bacterial HR caused by a single avirulence gene in the absence of other bacterial signals. We used dexamethasone (dex)-inducible transgenic Arabidopsis (Arabidopsis thaliana) plants containing the avrRpt2 gene from Pseudomonas syringae pv tomato. Membrane depolarization in these plants began 1 to 1.5 h after dex application, hours before electrolyte leakage. Progressive depolarization was a sensitive early indicator of HR that occurred only in Arabidopsis leaf cells expressing both avrRpt2 and a functional RPS2 gene. Hyperpolarization of fully depolarized membranes by fusicoccin, a fungal toxin that activates the H 1 -ATPase, indicates that depolarization did not result from a nonfunctional pump or leaky membranes. Depolarization and electrolyte leakage were inhibited in RPS2 plants by the calcium channel blocker LaCl 3 , highly correlating these events and suggesting that Ca 21 entry into cells is required for both. Also correlated were inhibition of depolarization, electrolyte leakage, and HR following salicylic acid pretreatment. In salicylic acid-pretreated RPS2 seedlings, avrRpt2 transcript was produced after dex treatment. However, AvrRpt2 protein accumulation was greatly reduced, suggesting a possible mechanism for inhibition of HR in plants with induced resistance. This experimental system is a very sensitive assay that lends itself to the dissection of physiological processes leading to HR in plants, and provides a baseline for future research within a genetic framework.Plants are resistant to infection by many pathogens. Plants expressing a resistance (R) gene rapidly initiate defense responses following contact with a pathogen that expresses a corresponding avirulence (avr) gene (Flor, 1971). Isogenic plants lacking the R gene fall prey to the pathogen. The hypersensitive response (HR), rapid cell collapse at the site of infection, is often dramatic evidence of resistance, particularly in bacteriainduced HR (Goodman and Novacky, 1994;Heath, 2000).Many defense responses associated with bacteriainduced HR have been described since Klement et al. (1964) first demonstrated the total collapse of nonhost plant leaves following infiltration of pathogenic bacteria. They include ion fluxes, increased salicylic acid (SA) production, membrane depolarization, and pathogenesis-related (PR) gene induction (Goodman and Novacky, 1994;Dangl et al., 1996; HammondKosack and Jones, 1996;Dangl and Jones, 2001). Yet, the mechanism of HR induction is not well understood.The functional significance of bacteria-induced HR also is not clear because defense responses and resistance can occur without HR. For example, systemically acquired resistance, resistance to a broad spectrum of pathogens, can be induced in normally susceptible plants by pathogen infection or application o...

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“…I n plant pathogens, the type III secretion system, termed Hrp, is required for pathogenicity on susceptible plants and is also essential for induction of a defense reaction called the hypersensitive response, on resistant plants (1)(2)(3)(4). The Hrp system consists of a secretion apparatus encoded by Ϸ25 hrp genes and its main function is to deliver virulence proteins (effectors) into plant cells (5)(6)(7).…”

mentioning

confidence: 99%

“…The Hrp system consists of a secretion apparatus encoded by Ϸ25 hrp genes and its main function is to deliver virulence proteins (effectors) into plant cells (5)(6)(7). A broadly conserved subset of the hrp genes (designated hrc) appears to encode the core components of the delivery apparatus (2). It has been proposed that these core components are involved in the recognition of the secretion signals carried by the effectors and are thus responsible for the promiscuous character of type III systems for heterologous secreted proteins (8)(9)(10).…”

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confidence: 99%

Structure of HrcQ _B -C, a conserved component of the bacterial type III secretion systems

Fadouloglou

Tampakaki²,

Glykos³

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

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Type III secretion systems enable plant and animal bacterial pathogens to deliver virulence proteins into the cytosol of eukaryotic host cells, causing a broad spectrum of diseases including bacteremia, septicemia, typhoid fever, and bubonic plague in mammals, and localized lesions, systemic wilting, and blights in plants. In addition, type III secretion systems are also required for biogenesis of the bacterial flagellum. The HrcQB protein, a component of the secretion apparatus of Pseudomonas syringae with homologues in all type III systems, has a variable N-terminal and a conserved C-terminal domain (HrcQB-C). Here, we report the crystal structure of HrcQB-C and show that this domain retains the ability of the full-length protein to interact with other type III components. A 3D analysis of sequence conservation patterns reveals two clusters of residues potentially involved in protein-protein interactions. Based on the analogies between HrcQB and its flagellum homologues, we propose that HrcQB-C participates in the formation of a C-ring-like assembly.

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The type III (Hrp) secretion pathway of plant pathogenic bacteria: trafficking harpins, Avr proteins, and death

Cited by 483 publications

References 89 publications

A dispensable region of the chromosome which is associated with an avirulence gene in Pseudomonas syringae pv. pisi

A dispensable region of the chromosome which is associated with an avirulence gene in Pseudomonas syringae pv. pisi

Electrophysiological Characterization of the Arabidopsis avrRpt2-Specific Hypersensitive Response in the Absence of Other Bacterial Signals

Structure of HrcQ _B -C, a conserved component of the bacterial type III secretion systems

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The type III (Hrp) secretion pathway of plant pathogenic bacteria: trafficking harpins, Avr proteins, and death

Cited by 483 publications

References 89 publications

A dispensable region of the chromosome which is associated with an avirulence gene in Pseudomonas syringae pv. pisi

A dispensable region of the chromosome which is associated with an avirulence gene in Pseudomonas syringae pv. pisi

Electrophysiological Characterization of the Arabidopsis avrRpt2-Specific Hypersensitive Response in the Absence of Other Bacterial Signals

Structure of HrcQ B -C, a conserved component of the bacterial type III secretion systems

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Structure of HrcQ _B -C, a conserved component of the bacterial type III secretion systems