scholarly journals A revised model for the role of GacS/GacA in regulating type III secretion by Pseudomonas syringae pv. tomato DC3000

2019 ◽  
Vol 21 (1) ◽  
pp. 139-144 ◽  
Author(s):  
Megan R. O’Malley ◽  
Ching‐Fang Chien ◽  
Scott C. Peck ◽  
Nai‐Chun Lin ◽  
Jeffrey C. Anderson
2020 ◽  
Vol 76 (7) ◽  
pp. 2294-2303 ◽  
Author(s):  
Ji Eun Kang ◽  
Byeong Jun Jeon ◽  
Min Young Park ◽  
Hye Ji Yang ◽  
Jaeyoung Kwon ◽  
...  

Microbiology ◽  
2005 ◽  
Vol 151 (1) ◽  
pp. 269-280 ◽  
Author(s):  
Ute Kabisch ◽  
Angelika Landgraf ◽  
Jana Krause ◽  
Ulla Bonas ◽  
Jens Boch

The hrp-type III secretion (TTS) system is a key pathogenicity factor of the plant pathogen Pseudomonas syringae pv. tomato DC3000 that translocates effector proteins into the cytosol of the eukaryotic host cell. The translocation of a subset of effectors is dependent on specific chaperones. In this study an operon encoding a TTS chaperone (ShcS1) and the truncated effector HopS1′ was characterized. Yeast two-hybrid analysis and pull-down assays demonstrated that these proteins interact. Using protein fusions to AvrRpt2 it was shown that ShcS1 facilitates the translocation of HopS1′, suggesting that ShcS1 is a TTS chaperone for HopS1′ and that amino acids 1 to 118 of HopS1′ are required for translocation. P. syringae pv. tomato DC3000 carries two shcS1 homologues, shcO1 and shcS2, which are located in different operons, and both operons include additional putative effector genes. Transcomplementation experiments showed that ShcS1 and ShcO1, but not ShcS2, can facilitate the translocation of HopS1′ : : AvrRpt2. To characterize the specificities of the putative chaperones, yeast two-hybrid interaction studies were performed between the three chaperones and putative target effectors. These experiments showed that both ShcS1 and ShcO1 bind to two different effectors, HopS1′ and HopO1-1, that share only 16 % amino acid sequence identity. Using gel filtration it was shown that ShcS1 forms homodimers, and this was confirmed by yeast two-hybrid experiments. In addition, ShcS1 is also able to form heterodimers with ShcO1. These data demonstrate that ShcS1 and ShcO1 are exceptional class IA TTS chaperones because they can bind more than one target effector.


2008 ◽  
Vol 21 (4) ◽  
pp. 490-502 ◽  
Author(s):  
Kathy R. Munkvold ◽  
Michael E. Martin ◽  
Philip A. Bronstein ◽  
Alan Collmer

The injection of nearly 30 effector proteins by the type III secretion system underlies the ability of Pseudomonas syringae pv. tomato DC3000 to cause disease in tomato and other host plants. The search for effector functions is complicated by redundancy within the repertoire and by plant resistance (R)-gene sentinels, which may convert effector virulence activities into a monolithic defense response. On the premise that some effectors target universal eukaryotic processes and that yeast (Saccharomyces cerevisiae) lacks R genes, the DC3000 effector repertoire was expressed in yeast. Of 27 effectors tested, HopAD1, HopAO1, HopD1, HopN1, and HopU1 were found to inhibit growth when expressed from a galactose-inducible GAL1 promoter, and HopAA1-1 and HopAM1 were found to cause cell death. Catalytic site mutations affecting the tyrosine phosphatase activity of HopAO1 and the cysteine protease activity of HopN1 prevented these effectors from inhibiting yeast growth. Expression of HopAA1-1, HopAM1, HopAD1, and HopAO1 impaired respiration in yeast, as indicated by tests with ethanol glycerol selective media. HopAA1-1 colocalized with porin to yeast mitochondria and was shown to cause cell death in yeast and plants in a domain-dependent manner. These results support the use of yeast for the study of plant-pathogen effector repertoires.


2004 ◽  
Vol 17 (5) ◽  
pp. 447-455 ◽  
Author(s):  
Libo Shan ◽  
Hye-sook Oh ◽  
Jianfu Chen ◽  
Ming Guo ◽  
Jianmin Zhou ◽  
...  

Type III secretion systes are highly conserved among gram-negative plant and animal pathogenic bacteria. Through the type III secretion system, bacteria inject a number of virulence proteins into the host cells. Analysis of the whole genome sequence of Pseudomonas syringae pv. tomato DC3000 strain identified a locus, named HopPtoF, that is homologous to the avirulence gene locus avrPphF in P. syringae pv. phaseolicola. The HopPtoF locus harbors two genes, ShcFPto and HopFPto, that are preceded by a single hrp box promoter. We present evidence here to show that ShcFPto and HopFPto encode a type III chaperone and a cognate effector, respectively. ShcFPto interacts with and stabilizes the HopFPto protein in the bacterial cell. Translation of HopFPto starts at a rare initiation codon ATA that limits the synthesis of the HopFPto protein to a low level in bacterial cells.


2015 ◽  
Vol 17 (6) ◽  
pp. 752-762 ◽  
Author(s):  
Hai-Lei Wei ◽  
Suma Chakravarthy ◽  
Johannes Mathieu ◽  
Tyler C. Helmann ◽  
Paul Stodghill ◽  
...  

2009 ◽  
Vol 5 (4) ◽  
pp. e1000388 ◽  
Author(s):  
Brian H. Kvitko ◽  
Duck Hwan Park ◽  
André C. Velásquez ◽  
Chia-Fong Wei ◽  
Alistair B. Russell ◽  
...  

2003 ◽  
Vol 16 (1) ◽  
pp. 43-52 ◽  
Author(s):  
Derrick E. Fouts ◽  
Jorge L. Badel ◽  
Adela R. Ramos ◽  
Ryan A. Rapp ◽  
Alan Collmer

The plant pathogenic species Pseudomonas syringae is divided into numerous pathovars based on host specificity. For example, P. syringae pv. tomato DC3000 is pathogenic on tomato and Arabidopsis, whereas P. syringae pv. syringae 61 is pathogenic on bean. The ability of P. syringae strains to elicit the hypersensitive response (HR) in non-hosts or be pathogenic (or parasitic) in hosts is dependent on the Hrp (type III secretion) system and effector proteins this system is thought to inject into plant cells. To test the role of the Hrp system in determining host range, the hrp/hrc gene cluster (hrpK through hrpR) was deleted from DC3000 and complemented in trans with the orthologous cluster from strain 61. Mutant CUCPB5114 expressing the bean pathogen Hrp system on plasmid pCPP2071 retained the ability of wild-type DC3000 to elicit the HR in bean, to grow and cause bacterial speck in tomato, and to elicit a cultivar-specific (gene-for-gene) HR in tomato plants carrying the Pto resistance gene. However, the symptoms produced in compatible tomato plants involved markedly reduced chlorosis, and CUCPB5114(pCPP2071) did not grow or produce symptoms in Arabidopsis Col-0 although it was weakly virulent in NahG Arabidopsis. A hypersensitive-like collapse was produced by CUCPB5114(pCPP2071) in Arabidopsis Col-0 at 1 × 107 CFU/ml, but only if the bacteria also expressed AvrB, which is recognized by the RPM1 resistance gene in Col-0 and confers incompatibility. These observations support the concept that the P. syringae effector proteins, rather than secretion system components, are the primary determinants of host range at both the species and cultivar levels of host specificity.


2007 ◽  
Vol 189 (22) ◽  
pp. 8059-8072 ◽  
Author(s):  
Brian H. Kvitko ◽  
Adela R. Ramos ◽  
Joanne E. Morello ◽  
Hye-Sook Oh ◽  
Alan Collmer

ABSTRACT Harpins are a subset of type III secretion system (T3SS) substrates found in all phytopathogenic bacteria that utilize a T3SS. Pseudomonas syringae pv. tomato DC3000 was previously reported to produce two harpins, HrpZ1 and HrpW1. DC3000 was shown here to deploy two additional proteins, HopAK1 and HopP1, which have the harpin-like properties of lacking cysteine, eliciting the hypersensitive response (HR) when partially purified and infiltrated into tobacco leaves, and possessing a two-domain structure similar to that of the HrpW1 class of harpins. Unlike the single-domain harpin HrpZ1, the two-domain harpins have C-terminal enzyme-like domains: pectate lyase for HopAK1 and lytic transglycosylase for HopP1. Genetic techniques to recycle antibiotic markers were applied to DC3000 to generate a quadruple harpin gene polymutant. The polymutant was moderately reduced in the elicitation of the HR and translocation of the T3SS effector AvrPto1 fused to a Cya translocation reporter, but the mutant was unaffected in the secretion of AvrPto1-Cya. The DC3000 hrpK1 gene encodes a putative translocator in the HrpF/NopX family and was deleted in combination with the four harpin genes. The hrpK1 quadruple harpin gene polymutant was strongly reduced in HR elicitation, virulence, and translocation of AvrPto1-Cya into plant cells but not in the secretion of representative T3SS substrates in culture. HrpK1, HrpZ1, HrpW1, and HopAK1, but not HopP1, were independently capable of restoring some HR elicitation to the hrpK1 quadruple harpin gene polymutant, which suggests that a consortium of semiredundant translocators from three protein classes cooperate to form the P. syringae T3SS translocon.


2009 ◽  
Vol 22 (11) ◽  
pp. 1341-1355 ◽  
Author(s):  
Kathy R. Munkvold ◽  
Alistair B. Russell ◽  
Brian H. Kvitko ◽  
Alan Collmer

The ability of Pseudomonas syringae pv. tomato DC3000 to cause bacterial speck disease in tomato is dependent on the injection, via the type III secretion system, of approximately 28 Avr/Hop effector proteins. HopAA1-1 is encoded in the conserved effector locus (CEL) of the P. syringae Hrp pathogenicity island. Transiently expressed HopAA1-1 acts inside Saccharomyces cerevisiae and plant cells to elicit cell death. hopAA1 homologs were cloned and sequenced from the CEL of seven P. syringae strains representing diverse pathovars. Analysis of the sequences revealed that HopAA1-1 carries a potential GTPase-activating protein (GAP) domain, GALRA, which is polymorphic (FEN instead of LRA) in HopAA1-2, a paralogous DC3000 effector. Deleting hopAA1-1 from DC3000 reduces the formation of necrotic speck lesions in dip-inoculated tomato leaves if effector-gene cluster IX or just PSPTO4723 within this region has been deleted. A HopAA1-1 mutant in which the putative catalytic arginine in the GAP-like domain has been replaced with alanine retains its ability to kill yeast and promote the formation of speck lesions by the ΔhopAA1-1ΔIX mutant, but a HopAA1-1 mutant carrying the FEN polymorphism loses both of these abilities. Unexpectedly, PSPTO4723 does not appear to encode an effector and its deletion also reduces disease-associated chlorosis.


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