Effector loss drives adaptation of Pseudomonas syringae pv. actinidiae to Actinidia arguta

A pandemic isolate of Pseudomonas syringae pv. actinidiae biovar 3 (Psa3) has devastated kiwifruit orchards growing cultivars of Actinidia chinensis. In contrast, A. arguta (kiwiberry) is resistant to Psa3. This resistance is mediated via effector-triggered immunity, as demonstrated by induction of the hypersensitive response in infected A. arguta leaves, observed by microscopy and quantified by ion-leakage assays. Isolates of Psa3 that cause disease in A. arguta have been isolated and analyzed, revealing a 49 kb deletion in the exchangeable effector locus (EEL). This natural EEL-mutant isolate and strains with synthetic knockouts of the EEL were more virulent in A. arguta plantlets than wild-type Psa3. Screening of a complete library of Psa3 effector knockout strains identified increased growth in planta for knockouts of four effectors — AvrRpm1a, HopF1c, HopZ5a, and the EEL effector HopAW1a — suggesting a resistance response in A. arguta. Hypersensitive response (HR) assays indicate that three of these effectors trigger a host species-specific HR. A Psa3 strain with all four effectors knocked out escaped host recognition, but a cumulative increase in bacterial pathogenicity and virulence was not observed. These avirulence effectors can be used in turn to identify the first cognate resistance genes in Actinidia for breeding durable resistance into future kiwifruit cultivars.

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Pseudomonas syringae Effector AvrPphB Suppresses AvrB-Induced Activation of RPM1 but Not AvrRpm1-Induced Activation

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-08-14-0248-r ◽

2015 ◽

Vol 28 (6) ◽

pp. 727-735 ◽

Cited By ~ 24

Author(s):

Andrew R. Russell ◽

Tom Ashfield ◽

Roger W. Innes

Keyword(s):

Disease Resistance ◽

Protein Kinase ◽

Molecular Mechanism ◽

Pseudomonas Syringae ◽

Hypersensitive Response ◽

Hypersensitive Resistance ◽

Nicotiana Glutinosa ◽

Resistance Response ◽

Interacting Protein ◽

Soybean Plants

The Pseudomonas syringae effector AvrB triggers a hypersensitive resistance response in Arabidopsis and soybean plants expressing the disease resistance (R) proteins RPM1 and Rpg1b, respectively. In Arabidopsis, AvrB induces RPM1-interacting protein kinase (RIPK) to phosphorylate a disease regulator known as RIN4, which subsequently activates RPM1-mediated defenses. Here, we show that AvrPphB can suppress activation of RPM1 by AvrB and this suppression is correlated with the cleavage of RIPK by AvrPphB. Significantly, AvrPphB does not suppress activation of RPM1 by AvrRpm1, suggesting that RIPK is not required for AvrRpm1-induced modification of RIN4. This observation indicates that AvrB and AvrRpm1 recognition is mediated by different mechanisms in Arabidopsis, despite their recognition being determined by a single R protein. Moreover, AvrB recognition but not AvrRpm1 recognition is suppressed by AvrPphB in soybean, suggesting that AvrB recognition requires a similar molecular mechanism in soybean and Arabidopsis. In support of this, we found that phosphodeficient mutations in the soybean GmRIN4a and GmRIN4b proteins are sufficient to block Rpg1b-mediated hypersensitive response in transient assays in Nicotiana glutinosa. Taken together, our results indicate that AvrB and AvrPphB target a conserved defense signaling pathway in Arabidopsis and soybean that includes RIPK and RIN4.

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HopA1 Effector from Pseudomonas syringae pv syringae Strain 61 Affects NMD Processes and Elicits Effector-Triggered Immunity

International Journal of Molecular Sciences ◽

10.3390/ijms22147440 ◽

2021 ◽

Vol 22 (14) ◽

pp. 7440

Author(s):

Shraddha K. Dahale ◽

Daipayan Ghosh ◽

Kishor D. Ingole ◽

Anup Chugani ◽

Sang Hee Kim ◽

...

Keyword(s):

Pseudomonas Syringae ◽

Disease Susceptibility ◽

Null Mutant ◽

In Planta ◽

Host Range Expansion ◽

Unique System ◽

Effector Triggered Immunity ◽

Transcriptomic Changes ◽

Immune Detection

Pseudomonas syringae-secreted HopA1 effectors are important determinants in host range expansion and increased pathogenicity. Their recent acquisitions via horizontal gene transfer in several non-pathogenic Pseudomonas strains worldwide have caused alarming increase in their virulence capabilities. In Arabidopsis thaliana, RESISTANCE TO PSEUDOMONAS SYRINGAE 6 (RPS6) gene confers effector-triggered immunity (ETI) against HopA1pss derived from P. syringae pv. syringae strain 61. Surprisingly, a closely related HopA1pst from the tomato pathovar evades immune detection. These responsive differences in planta between the two HopA1s represents a unique system to study pathogen adaptation skills and host-jumps. However, molecular understanding of HopA1′s contribution to overall virulence remain undeciphered. Here, we show that immune-suppressive functions of HopA1pst are more potent than HopA1pss. In the resistance-compromised ENHANCED DISEASE SUSCEPTIBILITY 1 (EDS1) null-mutant, transcriptomic changes associated with HopA1pss-elicited ETI are still induced and carry resemblance to PAMP-triggered immunity (PTI) signatures. Enrichment of HopA1pss interactome identifies proteins with regulatory roles in post-transcriptional and translational processes. With our demonstration here that both HopA1 suppress reporter-gene translations in vitro imply that the above effector-associations with plant target carry inhibitory consequences. Overall, with our results here we unravel possible virulence role(s) of HopA1 in suppressing PTI and provide newer insights into its detection in resistant plants.

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The Majority of the Type III Effector Inventory of Pseudomonas syringae pv. tomato DC3000 Can Suppress Plant Immunity

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-22-9-1069 ◽

2009 ◽

Vol 22 (9) ◽

pp. 1069-1080 ◽

Cited By ~ 147

Author(s):

Ming Guo ◽

Fang Tian ◽

Yashitola Wamboldt ◽

James R. Alfano

Keyword(s):

Pseudomonas Syringae ◽

Plant Immunity ◽

In Planta ◽

Tomato Dc3000 ◽

Type Iii Effector ◽

Type Iii Effectors ◽

Type Iii ◽

Molecular Pattern ◽

Effector Triggered Immunity ◽

Type Iii Protein Secretion

The Pseudomonas syringae type III protein secretion system (T3SS) and the type III effectors it injects into plant cells are required for plant pathogenicity and the ability to elicit a hypersensitive response (HR). The HR is a programmed cell death that is associated with effector-triggered immunity (ETI). A primary function of P. syringae type III effectors appears to be the suppression of ETI and pathogen-associated molecular pattern–triggered immunity (PTI), which is induced by conserved molecules on microorganisms. We reported that seven type III effectors from P. syringae pv. tomato DC3000 were capable of suppressing an HR induced by P. fluorescens(pHIR11) and have now tested 35 DC3000 type III effectors in this assay, finding that the majority of them can suppress the HR induced by HopA1. One newly identified type III effector with particularly strong HR suppression activity was HopS2. We used the pHIR11 derivative pLN1965, which lacks hopA1, in related assays and found that a subset of the type III effectors that suppressed HopA1-induced ETI also suppressed an ETI response induced by AvrRpm1 in Arabidopsis thaliana. A. thaliana plants expressing either HopAO1 or HopF2, two type III effectors that suppressed the HopA1-induced HR, were reduced in the flagellin-induced PTI response as well as PTI induced by other PAMPs and allowed enhanced in planta growth of P. syringae. Collectively, our results suggest that the majority of DC3000 type III effectors can suppress plant immunity. Additionally, the construct pLN1965 will likely be a useful tool in determining whether other type III effectors or effectors from other types of pathogens can suppress either ETI, PTI, or both.

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Specific In Planta Recognition of Two GKLR Proteins of the Downy Mildew Bremia lactucae Revealed in a Large Effector Screen in Lettuce

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-05-13-0142-r ◽

2013 ◽

Vol 26 (11) ◽

pp. 1259-1270 ◽

Cited By ~ 29

Author(s):

Joost H. M. Stassen ◽

Erik den Boer ◽

Pim W. J. Vergeer ◽

Annemiek Andel ◽

Ursula Ellendorff ◽

...

Keyword(s):

Immune Responses ◽

Downy Mildew ◽

Hypersensitive Response ◽

Effector Proteins ◽

Chromosome 9 ◽

Downy Mildew Resistance ◽

Chromosome 2 ◽

Bremia Lactucae ◽

In Planta ◽

Effector Triggered Immunity

Breeding lettuce (Lactuca sativa) for resistance to the downy mildew pathogen Bremia lactucae is mainly achieved by introgression of dominant downy mildew resistance (Dm) genes. New Bremia races quickly render Dm genes ineffective, possibly by mutation of recognized host-translocated effectors or by suppression of effector-triggered immunity. We have previously identified 34 potential RXLR(-like) effector proteins of B. lactucae that were here tested for specific recognition within a collection of 129 B. lactucae-resistant Lactuca lines. Two effectors triggered a hypersensitive response: BLG01 in 52 lines, predominantly L. saligna, and BLG03 in two L. sativa lines containing Dm2 resistance. The N-terminal sequences of BLG01 and BLG03, containing the signal peptide and GKLR variant of the RXLR translocation motif, are not required for in planta recognition but function in effector delivery. The locus responsible for BLG01 recognition maps to the bottom of lettuce chromosome 9, whereas recognition of BLG03 maps in the RGC2 cluster on chromosome 2. Lactuca lines that recognize the BLG effectors are not resistant to Bremia isolate Bl:24 that expresses both BLG genes, suggesting that Bl:24 can suppress the triggered immune responses. In contrast, lettuce segregants displaying Dm2-mediated resistance to Bremia isolate Bl:5 are responsive to BLG03, suggesting that BLG03 is a candidate Avr2 protein.

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A Pseudomonas syringae pv. tomato avrE1/hopM1 Mutant Is Severely Reduced in Growth and Lesion Formation in Tomato

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-19-0099 ◽

2006 ◽

Vol 19 (2) ◽

pp. 99-111 ◽

Cited By ~ 99

Author(s):

Jorge L. Badel ◽

Rena Shimizu ◽

Hye-Sook Oh ◽

Alan Collmer

Keyword(s):

Pseudomonas Syringae ◽

Hypersensitive Response ◽

Plant Cells ◽

Effector Proteins ◽

35S Promoter ◽

In Planta ◽

Lesion Formation ◽

Effector Genes ◽

Combined Action ◽

Different Levels

The model plant pathogen Pseudomonas syringae pv. tomato DC3000 grows and produces necrotic lesions in the leaves of its host, tomato. Both abilities are dependent upon the hypersensitive response and pathogenicity (Hrp) type III secretion system (TTSS), which translocates multiple effector proteins into plant cells. A previously constructed DC3000 mutant with a 9.3-kb deletion in the Hrp pathogenicity island conserved effector locus (CEL) was strongly reduced in growth and lesion formation in tomato leaves. The ΔCEL mutation affects three putative or known effector genes: avrE1, hopM1, and hopAA1-1. Comparison of genomic sequences of DC3000, P. syringae pv. phaseolicola 1448A, and P. syringae pv. syringae B728a revealed that these are the only effector genes present in the CEL of all three strains. AvrE1 was shown to carry functional TTSS translocation signals based on the performance of a fusion of the first 315 amino acids of AvrE1 to the Cya translocation reporter. A DC3000 ΔavrE1 mutant was reduced in its ability to produce lesions but not in its ability to grow in host tomato leaves. AvrE1 expressed from the 35S promoter elicited cell death in nonhost Nicotiana tabacum leaves and host tomato leaves in Agrobacterium-mediated transient expression experiments. Mutations involving combinations of avrE1, hopM1, and hopAA1-1 revealed that deletion of both avrE1 and hopM1 reproduced the strongly reduced growth and lesion phenotype of the ΔCEL mutant. Furthermore, quantitative assays involving different levels of inoculum and electrolyte leakage revealed that the avrE1/hopM1 and ΔCEL mutants both were partially impaired in their ability to elicit the hypersensitive response in nonhost N. benthamiana leaves. However, the avrE1/hopM1 mutant was not impaired in its ability to deliver AvrPto1(1–100)-Cya to nonhost N. benthamiana or host tomato leaves during the first 9 h after inoculation. These data suggest that AvrE1 acts within plant cells and promotes lesion formation and that the combined action of AvrE1 and HopM1 is particularly important in promoting bacterial growth in planta.

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Basal Resistance Against Pseudomonas syringae in Arabidopsis Involves WRKY53 and a Protein with Homology to a Nematode Resistance Protein

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-20-11-1431 ◽

2007 ◽

Vol 20 (11) ◽

pp. 1431-1438 ◽

Cited By ~ 82

Author(s):

Shane L. Murray ◽

Robert A. Ingle ◽

Lindsay N. Petersen ◽

Katherine J. Denby

Keyword(s):

Pseudomonas Syringae ◽

Bacterial Pathogen ◽

Nematode Resistance ◽

Host Recognition ◽

In Planta ◽

Basal Resistance ◽

Pathogen Effectors ◽

Positive Regulators ◽

Resistance Protein ◽

Molecular Patterns

Basal resistance is the ultimately unsuccessful plant defense response to infection with a virulent pathogen. It is thought to be triggered by host recognition of pathogen-associated molecular patterns, with subsequent suppression of particular components by pathogen effectors. To identify novel components of Arabidopsis basal resistance against the bacterial pathogen Pseudomonas syringae pv. tomato, microarray expression profiling was carried out on the cir1 mutant, which displays enhanced resistance against P. syringae pv. tomato. This identified two genes, At4g23810 and At2g40000, encoding the transcription factor WRKY53 and the nematode resistance protein-like HSPRO2, whose expression was upregulated in cir1 prior to pathogen infection and in wild-type plants after P. syringae pv. tomato infection. WRKY53 and HSPRO2 are positive regulators of basal resistance. Knockout mutants of both genes were more susceptible to P. syringae pv. tomato infection than complemented lines, with increased growth of the pathogen in planta. WRKY53 and HSPRO2 appear to function downstream of salicylic acid and to be negatively regulated by signaling through jasmonic acid and ethylene.

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Elicitation of Hypersensitive Cell Death by Extracellularly Targeted HrpZPsph Produced In Planta

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi.2000.13.12.1366 ◽

2000 ◽

Vol 13 (12) ◽

pp. 1366-1374 ◽

Cited By ~ 35

Author(s):

Anastasia P. Tampakaki ◽

Nickolas J. Panopoulos

Keyword(s):

Pseudomonas Syringae ◽

Hypersensitive Response ◽

Active Form ◽

Biologically Active ◽

Specific Gene ◽

Gene Transcript ◽

In Planta ◽

Hypersensitive Cell Death ◽

Pathogenesis Related Protein ◽

High Concentrations

The ability of the Pseudomonas syringae pv. phaseolicola harpin (HrpZPsph) to elicit hypersensitive response was investigated in three Nicotiana genotypes. The hrpZPsph gene was placed under chemical regulation (tetracycline induction) in TetR+ Nicotiana tabacum cv. Wisconsin 38 (W38) or was transiently expressed in N. benthamiana following infection with a PVX-derived vector and in three Nicotiana genotypes by agroinfiltration. The constructs were designed to express either the canonical form of harpin (HrpZPsph) or an N-terminally extended version of the protein carrying the signal peptide portion of the tobacco pathogenesis-related protein PR1a (SP-HrpZPsph). Stable transformants of N. tabacum cv. W38 did not develop necrosis upon induction with tetracycline, probably as a result of insufficient harpin accumulation. In contrast, N. benthamiana plants infected with the PVX constructs produced high concentrations of harpin in biologically active form, but only those expressing the secretable form of harpin developed necrotic symptoms. These symptoms were less severe than those caused by PVX∷avrPto; however, they were accompanied by induction of hsr203J, a hypersensitive response-specific gene transcript. These results suggest that the plant cellular receptor(s) for harpin is extracellular.

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Feedback Control of the Arabidopsis Hypersensitive Response

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi.2004.17.4.357 ◽

2004 ◽

Vol 17 (4) ◽

pp. 357-365 ◽

Cited By ~ 13

Author(s):

Chu Zhang ◽

Annie Tang Gutsche ◽

Allan D. Shapiro

Keyword(s):

Hydrogen Peroxide ◽

Salicylic Acid ◽

Pseudomonas Syringae ◽

Hypersensitive Response ◽

Ion Leakage ◽

Wild Type ◽

Regulatory Circuits ◽

Acid Accumulation ◽

Salicylic Acid Accumulation ◽

Hydrogen Peroxide Accumulation

The plant hypersensitive response (HR) to avirulent bacterial pathogens results from programmed cell death of plant cells in the infected region. Ion leakage and changes in signaling components associated with HR progression were measured. These studies compared Arabidopsis mutants affecting feedback loops with wild-type plants, with timepoints taken hourly. In response to Pseudomonas syringae pv. tomato DC3000·avrB, npr1-2 mutant plants showed increased ion leakage relative to wild-type plants. Hydrogen peroxide accumulation was similar to that in wild type, but salicylic acid accumulation was reduced at some timepoints. With DC3000·avrRpt2, similar trends were seen. In response to DC3000·avrB, ndr1-1 mutant plants showed more ion leakage than wild-type or npr1-2 plants. Hydrogen peroxide accumulation was delayed by approximately 1 h and reached half the level seen with wild-type plants. Salicylic acid accumulation was similar to npr1-2 mutant plants. With DC3000·avrRpt2, ndr1-1 mutant plants showed no ion leakage, no hydrogen peroxide accumulation, and minimal salicylic acid accumulation. Results with a ndr1-1 and npr1-2 double mutant were similar to ndr1-1. A model consistent with these data is presented, in which one positive and two negative regulatory circuits control HR progression. Understanding this circuitry will facilitate HR manipulation for enhanced disease resistance.

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Paraburkholderia phytofirmans PsJN Protects Arabidopsis thaliana Against a Virulent Strain of Pseudomonas syringae Through the Activation of Induced Resistance

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-09-16-0192-r ◽

2017 ◽

Vol 30 (3) ◽

pp. 215-230 ◽

Cited By ~ 20

Author(s):

Tania Timmermann ◽

Grace Armijo ◽

Raúl Donoso ◽

Aldo Seguel ◽

Loreto Holuigue ◽

...

Keyword(s):

Plant Growth ◽

Disease Severity ◽

Induced Resistance ◽

Pseudomonas Syringae ◽

Virulent Strain ◽

Host Recognition ◽

Resistance Response ◽

Molecular Pattern ◽

Plant Growth Promoting ◽

Resistance To Infection

Paraburkholderia phytofirmans PsJN is a plant growth–promoting rhizobacterium (PGPR) that stimulates plant growth and improves tolerance to abiotic stresses. This study analyzed whether strain PsJN can reduce plant disease severity and proliferation of the virulent strain Pseudomonas syringae pv. tomato DC3000, in Arabidopsis plants, through the activation of induced resistance. Arabidopsis plants previously exposed to strain PsJN showed a reduction in disease severity and pathogen proliferation in leaves compared with noninoculated, infected plants. The plant defense-related genes WRKY54, PR1, ERF1, and PDF1.2 demonstrated increased and more rapid expression in strain PsJN-treated plants compared with noninoculated, infected plants. Transcriptional analyses and functional analysis using signaling mutant plants suggested that resistance to infection by DC3000 in plants treated with strain PsJN involves salicylic acid–, jasmonate-, and ethylene-signaling pathways to activate defense genes. Additionally, activation occurs through a specific PGPR-host recognition, being a necessary metabolically active state of the bacterium to trigger the resistance in Arabidopsis, with a strain PsJN–associated molecular pattern only partially involved in the resistance response. This study provides the first report on the mechanism used by the PGPR P. phytofirmans PsJN to protect A. thaliana against a widespread virulent pathogenic bacterium.

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Nuclear Localization of HopA1Pss61 Is Required for Effector-Triggered Immunity

Plants ◽

10.3390/plants10050888 ◽

2021 ◽

Vol 10 (5) ◽

pp. 888

Author(s):

Hobin Kang ◽

Quang-Minh Nguyen ◽

Arya Bagus Boedi Iswanto ◽

Jong Chan Hong ◽

Saikat Bhattacharjee ◽

...

Keyword(s):

Cell Death ◽

Pseudomonas Syringae ◽

Nuclear Localization ◽

Functional Characterization ◽

Defense Responses ◽

Disease Resistance Gene ◽

In Planta ◽

Resistance Proteins ◽

Cell Death Response ◽

Effector Triggered Immunity

Plant resistance proteins recognize cognate pathogen avirulence proteins (also named effectors) to implement the innate immune responses called effector-triggered immunity. Previously, we reported that hopA1 from Pseudomonas syringae pv. syringae strain 61 was identified as an avr gene for Arabidopsis thaliana. Using a forward genetic screen approach, we cloned a hopA1-specific TIR-NBS-LRR class disease resistance gene, RESISTANCE TO PSEUDOMONAS SYRINGAE6 (RPS6). Many resistance proteins indirectly recognize effectors, and RPS6 is thought to interact with HopA1Pss61 indirectly by surveillance of an effector target. However, the involved target protein is currently unknown. Here, we show RPS6 is the only R protein that recognizes HopA1Pss61 in Arabidopsis wild-type Col-0 accession. Both RPS6 and HopA1Pss61 are co-localized to the nucleus and cytoplasm. HopA1Pss61 is also distributed in plasma membrane and plasmodesmata. Interestingly, nuclear localization of HopA1Pss61 is required to induce cell death as NES-HopA1Pss61 suppresses the level of cell death in Nicotiana benthamiana. In addition, in planta expression of hopA1Pss61 led to defense responses, such as a dwarf morphology, a cell death response, inhibition of bacterial growth, and increased accumulation of defense marker proteins in transgenic Arabidopsis. Functional characterization of HopA1Pss61 and RPS6 will provide an important piece of the ETI puzzle.

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