scholarly journals Xanthomonas campestris pv. vesicatoria Effector AvrBsT Induces Cell Death in Pepper, but Suppresses Defense Responses in Tomato

2010 ◽  
Vol 23 (8) ◽  
pp. 1069-1082 ◽  
Author(s):  
Nak Hyun Kim ◽  
Hyong Woo Choi ◽  
Byung Kook Hwang
Keyword(s):  
Xanthomonas Campestris ◽  
Marker Gene ◽  
Defense Responses ◽  
Gene Expressions ◽  
Callose Deposition ◽  
Tomato Plants ◽  
Type Iii Effector ◽  
Type Iii ◽  
Pepper Leaves ◽  
Pepper Plants

A type III effector protein, AvrBsT, is secreted into plant cells from Xanthomonas campestris pv. vesicatoria Bv5-4a, which causes bacterial spot disease on pepper (Capsicum annuum) and tomato (Solanum lycopersicum). To define the function and recognition of AvrBsT in the two host plants, avrBsT was introduced into the virulent pepper strain X. campestris pv. vesicatoria Ds1. Expression of AvrBsT in Ds1 rendered the strain avirulent to pepper plants. Infection of pepper leaves with Ds1 (avrBsT) expressing AvrBsT but not with near-isogenic control strains triggered a hypersensitive response (HR) accompanied by strong H2O2 generation, callose deposition, and defense-marker gene expressions. Mutation of avrBsT, however, compromised HR induction by X. campestris pv. vesicatoria Bv5-4a, suggesting its avirulence function in pepper plants. In contrast, AvrBsT acted as a virulence factor in tomato plants. Growth of strains Ds1 (avrBsT) and Bv5-4a ΔavrBsT was significantly enhanced and reduced, respectively, in tomato leaves. X. campestris pv. vesicatoria-expressed AvrBsT also significantly compromised callose deposition and defense-marker gene expression in tomato plants. Together, these results suggest that the X. campestris pv. vesicatoria type III effector AvrBsT is differentially recognized by pepper and tomato plants.

scholarly journals DspA/E, a Type III Effector Essential for Erwinia amylovora Pathogenicity and Growth In Planta, Induces Cell Death in Host Apple and Nonhost Tobacco Plants

2006 ◽  
Vol 19 (1) ◽  
pp. 16-24 ◽  
Author(s):  
Tristan Boureau ◽  
Hayat ElMaarouf-Bouteau ◽  
Amélie Garnier ◽  
Marie-Noëlle Brisset ◽  
Claude Perino ◽  
...  
Keyword(s):  
Cell Death ◽  
Type Iii Secretion ◽  
Erwinia Amylovora ◽  
Marker Gene ◽  
Defense Responses ◽  
In Planta ◽  
Callose Deposition ◽  
Type Iii Effector ◽  
Type Iii

Erwinia amylovora is responsible for fire blight, a necrotic disease of apples and pears. E. amylovora relies on a type III secretion system (TTSS) to induce disease on hosts and hypersensitive response (HR) on nonhost plants. The DspA/E protein is essential for E. amylovora pathogenicity and is secreted via the TTSS in vitro. DspA/E belongs to a type III effector family that is conserved in several phytopathogenic bacteria. In E. amylovora, DspA/E has been implicated in the generation of an oxidative stress during disease and the suppression of callose deposition. We investigated the fate of DspA/E in planta. DspA/E delivered artificially to apple or tobacco cells by agroinfection induced necrotic symptoms, indicating that DspA/E was probably injected via the TTSS. We confirmed that DspA/E acts as a major cell-death inducer during disease and HR, because the dspA/E mutant is severely impaired in its ability to induce electrolyte leakage in apple and tobacco leaves. Expression of the defense marker gene PR1 was delayed when dspA/E was transiently expressed in tobacco, suggesting that DspA/E-mediated necrosis may be associated with an alteration of defense responses.

scholarly journals The Xanthomonas type-III effector protein XopS stabilizes CaWRKY40a to regulate defense hormone responses and preinvasion immunity in pepper (Capsicum annuum)

2021 ◽  
Author(s):  
Margot Raffeiner ◽  
Suayib Üstün ◽  
Tiziana Guerra ◽  
Daniela Spinti ◽  
Maria Fitzner ◽  
...  
Keyword(s):  
Gene Expression ◽  
Xanthomonas Campestris ◽  
Stomatal Closure ◽  
Ectopic Expression ◽  
Defense Responses ◽  
Dependent Manner ◽  
Plant Tolerance ◽  
Defense Gene Expression ◽  
Type Iii Effector ◽  
Type Iii

A critical component of plant immunity against invading pathogens is the rapid transcriptional reprogramming of the attacked cell to minimize virulence. Many adapted plant bacterial pathogens use type III effector (T3E) proteins to interfere with plant defense responses, including the induction of immunity genes. The elucidation of effector function is essential to understanding bacterial pathogenesis. Here, we show that XopS, a T3E of Xanthomonas campestris pv. vesicatoria (Xcv), interacts with and inhibits the proteasomal degradation of the transcriptional regulator of defense gene expression WRKY40. Virus-induced gene silencing of WRKY40 in pepper enhanced plant tolerance towards Xcv infection, indicating it represses immunity. Stabilization of WRKY40 by XopS reduces the expression of its targets including salicylic acid (SA)-responsive genes and the jasmonic acid (JA) signaling repressor JAZ8. Xcv bacteria lacking XopS display significantly reduced virulence when surface inoculated onto susceptible pepper leaves. XopS delivery by Xcv, as well as ectopic expression of XopS in Arabidopsis or Nicotiana benthamiana prevented stomatal closure in response to bacteria and biotic elicitors in a WRKY40 dependent manner. This suggests that XopS interferes with preinvasion as well as with apoplastic defense by manipulating WRKY40 stability and gene expression eventually altering phytohormone crosstalk to promote pathogen proliferation.

scholarly journals Basal Defenses Induced in Pepper by Lipopolysaccharides Are Suppressed by Xanthomonas campestris pv. vesicatoria

2004 ◽  
Vol 17 (7) ◽  
pp. 805-815 ◽  
Author(s):  
Mansureh Keshavarzi ◽  
Soner Soylu ◽  
Ian Brown ◽  
Ulla Bonas ◽  
Michel Nicole ◽  
...  
Keyword(s):  
Xanthomonas Campestris ◽  
Structural Changes ◽  
Plant Cell Wall ◽  
Defense Responses ◽  
Effector Proteins ◽  
Wild Type ◽  
Callose Deposition ◽  
Pepper Leaves ◽  
Mixed Inocula ◽  
Basal Defense

The nonpathogenic hrcC mutant of Xanthomonas campestris pv. vesicatoria 85-10∷hrpA22 multiplied in pepper leaves if it was mixed with pathogenic strains of X. campestris pv. vesicatoria. Reactions to the mutant alone included localized deposition of phenolics and callose in papillae, and alterations to the plant cell wall leading to increased electron density. Electron microscopy showed that the localized responses were suppressed in the presence of wild-type bacteria but other wall changes occurred at some sites, involving cellulose-rich ingrowth of the wall. Multiplication of the hrp mutant in mixed inocula was confirmed by tagging 85-10∷hrpA22 using immunocytochemical location of AvrBs3 expressed from the plasmid pD36. Elicitors of callose deposition and other wall changes were isolated from the hrcC mutant. Activity in extracts of bacteria was attributed to the presence of high molecular weight lipopolysaccharides (LPS). Wild-type X. campestris pv. vesicatoria suppressed induction of structural changes caused by purified LPS. Results obtained suggest that effector proteins produced by phytopathogenic bacteria and delivered by the type III secretion system may have a key role in suppressing the basal defense responses activated by bacterial LPS, which lead to restricted multiplication of nonpathogens such as hrp mutants.

scholarly journals Chitinase Gene Positively Regulates Hypersensitive and Defense Responses of Pepper to Colletotrichum acutatum Infection

2020 ◽  
Vol 21 (18) ◽  
pp. 6624 ◽  
Author(s):  
Muhammad Ali ◽  
Quan-Hui Li ◽  
Tao Zou ◽  
Ai-Min Wei ◽  
Ganbat Gombojab ◽  
...  
Keyword(s):  
Defense Response ◽  
Defense Responses ◽  
Chitinase Gene ◽  
Colletotrichum Acutatum ◽  
Basal Resistance ◽  
Chitin Binding Domain ◽  
Pepper Leaves ◽  
Defense Response Genes ◽  
Chitinase Genes ◽  
Pepper Plants

Anthracnose caused by Colletotrichum acutatum is one of the most devastating fungal diseases of pepper (Capsicum annuum L.). The utilization of chitin-binding proteins or chitinase genes is the best option to control this disease. A chitin-binding domain (CBD) has been shown to be crucial for the innate immunity of plants and activates the hypersensitive response (HR). The CaChiIII7 chitinase gene has been identified and isolated from pepper plants. CaChiIII7 has repeated CBDs that encode a chitinase enzyme that is transcriptionally stimulated by C. acutatum infection. The knockdown of CaChiIII7 in pepper plants confers increased hypersensitivity to C. acutatum, resulting in its proliferation in infected leaves and an attenuation of the defense response genes CaPR1, CaPR5, and SAR8.2 in the CaChiIII7-silenced pepper plants. Additionally, H2O2 accumulation, conductivity, proline biosynthesis, and root activity were distinctly reduced in CaChiIII7-silenced plants. Subcellular localization analyses indicated that the CaChiIII7 protein is located in the plasma membrane and cytoplasm of plant cells. The transient expression of CaChiIII7 increases the basal resistance to C. acutatum by significantly expressing several defense response genes and the HR in pepper leaves, accompanied by an induction of H2O2 biosynthesis. These findings demonstrate that CaChiIII7 plays a prominent role in plant defense in response to pathogen infection.

scholarly journals Characterization, Phylogeny, and Genome Analyses of Nonpathogenic Xanthomonas campestris Strains Isolated from Brassica Seeds

2020 ◽  
Vol 110 (5) ◽  
pp. 981-988 ◽  
Author(s):  
Yung-An Lee ◽  
Pei-Yu Yang ◽  
Shau-Chang Huang
Keyword(s):  
Type Iii Secretion ◽  
Xanthomonas Campestris ◽  
Pathogenicity Island ◽  
Whole Genome Sequence ◽  
Effector Protein ◽  
Type Iii Effector ◽  
Type Iii ◽  
Effector Genes ◽  
Genome Analyses ◽  
Xanthomonas Campestris Pv Campestris

Xanthomonads were detected by using the Xan-D(CCF) medium from the brassica seeds, and their pathogenicity was determined by plant inoculation tests. It was found that some seed lots were infested with Xanthomonas campestris pv. campestris, some with X. campestris pv. raphani, and some with nonpathogenic xanthomonads. The nonpathogenic xanthomonad strains were identified as X. campestris, and the multilocus sequence analysis showed that the nonpathogenic X. campestris strains were grouped together with pathogenic X. campestris, but not with nonpathogenic strains of X. arboricola. In addition, all isolated X. campestris pv. campestris and X. campestris pv. raphani strains were positive in the hrpF-PCR, but the nonpathogenic strains were negative. It was further found that nonpathogenic X. campestris strain nE1 does not contain the entire pathogenicity island (hrp gene cluster; type III secretion system) and all type III effector protein genes based on the whole genome sequence analyses. The nonpathogenic X. campestris strain nE1 could acquire the entire pathogenicity island from the endemic X. campestris pv. campestris and X. campestris pv. raphani strains by conjugation, but type III effector genes were not cotransferred. The studies showed that the nonpathogenic X. campestris strains indeed exist on the brassica seeds, but it could be differentiated by the PCR assays on the hrp and type III effector genes. Nevertheless, the nonpathogenic X. campestris strains cannot be ignored because they may be potential gene resources to increase genetic diversity in the endemic pathogenic X. campestris pv. campestris and X. campestris pv. raphani strains.

scholarly journals Xanthan Pyruvilation Is Essential for the Virulence of Xanthomonas campestris pv. campestris

2016 ◽  
Vol 29 (9) ◽  
pp. 688-699 ◽  
Author(s):  
María Isabel Bianco ◽  
Laila Toum ◽  
Pablo Marcelo Yaryura ◽  
Natalia Mielnichuk ◽  
Gustavo Eduardo Gudesblat ◽  
...  
Keyword(s):  
Xanthomonas Campestris ◽  
Defense Responses ◽  
Plant Defense Responses ◽  
In Planta ◽  
Callose Deposition ◽  
Disease Symptoms ◽  
The Relationship ◽  
Plant Surfaces ◽  
Xanthomonas Campestris Pv Campestris ◽  
Successful Colonization

Xanthan, the main exopolysaccharide (EPS) synthesized by Xanthomonas spp., contributes to bacterial stress tolerance and enhances attachment to plant surfaces by helping in biofilm formation. Therefore, xanthan is essential for successful colonization and growth in planta and has also been proposed to be involved in the promotion of pathogenesis by calcium ion chelation and, hence, in the suppression of the plant defense responses in which this cation acts as a signal. The aim of this work was to study the relationship between xanthan structure and its role as a virulence factor. We analyzed four Xanthomonas campestris pv. campestris mutants that synthesize structural variants of xanthan. We found that the lack of acetyl groups that decorate the internal mannose residues, ketal-pyruvate groups, and external mannose residues affects bacterial adhesion and biofilm architecture. In addition, the mutants that synthesized EPS without pyruvilation or without the external mannose residues did not develop disease symptoms in Arabidopsis thaliana. We also observed that the presence of the external mannose residues and, hence, pyruvilation is required for xanthan to suppress callose deposition as well as to interfere with stomatal defense. In conclusion, pyruvilation of xanthan seems to be essential for Xanthomonas campestris pv. campestris virulence.

scholarly journals Tomato SOBIR1/EVR Homologs Are Involved in Elicitin Perception and Plant Defense Against the Oomycete Pathogen Phytophthora parasitica

2015 ◽  
Vol 28 (8) ◽  
pp. 913-926 ◽  
Author(s):  
Ke-Chun Peng ◽  
Chao-Wen Wang ◽  
Chih-Hang Wu ◽  
Chun-Tzu Huang ◽  
Ruey-Fen Liou
Keyword(s):  
Cell Death ◽  
Plant Defense ◽  
Marker Gene ◽  
Defense Responses ◽  
Kinase Domain ◽  
Phytophthora Parasitica ◽  
Callose Deposition ◽  
Molecular Pattern ◽  
Molecular Events ◽  
Species Production

During host-pathogen interactions, pattern recognition receptors form complexes with proteins, such as receptor-like kinases, to elicit pathogen-associated molecular pattern-triggered immunity (PTI), an evolutionarily conserved plant defense program. However, little is known about the components of the receptor complex, as are the molecular events leading to PTI induced by the oomycete Phytophthora pathogen. Here, we demonstrate that tomato (Solanum lycopersicum) SlSOBIR1 and SlSOBIR1-like genes are involved in defense responses to Phytophthora parasitica. Silencing of SlSOBIR1 and SlSOBIR1-like enhanced susceptibility to P. parasitica in tomato. Callose deposition, reactive oxygen species production, and PTI marker gene expression were compromised in SlSOBIR1- and SlSOBIR1-like–silenced plants. Interestingly, P. parasitica infection and elicitin (ParA1) treatment induced the relocalization of SlSOBIR1 from the plasma membrane to endosomal compartments and silencing of NbSOBIR1 compromised ParA1-mediated cell death on Nicotiana benthamiana. Moreover, the SlSOBIR1 kinase domain is indispensable for ParA1 to trigger SlSOBIR1 internalization and plant cell death. Taken together, these results support the idea of participation of solanaceous SOBIR1/EVR homologs in the perception of elicitins and indicate their important roles in plant basal defense against oomycete pathogens.

scholarly journals The Xanthomonas campestris pv. vesicatoria Type III Effector Protein XopJ Inhibits Protein Secretion: Evidence for Interference with Cell Wall–Associated Defense Responses

2009 ◽  
Vol 22 (6) ◽  
pp. 655-664 ◽  
Author(s):  
Verena Bartetzko ◽  
Sophia Sonnewald ◽  
Florian Vogel ◽  
Kristina Hartner ◽  
Ruth Stadler ◽  
...  
Keyword(s):  
Cell Wall ◽  
Pseudomonas Syringae ◽  
Protein Secretion ◽  
Xanthomonas Campestris ◽  
Plant Cells ◽  
Defense Responses ◽  
Laser Scanning Microscopy ◽  
Phytopathogenic Bacterium ◽  
Type Iii ◽  
Gfp Fluorescence

The phytopathogenic bacterium Xanthomonas campestris pv. vesicatoria uses the type III secretion system (T3SS) to inject effector proteins into cells of its Solanaceous host plants. It is generally assumed that these effectors manipulate host pathways to favor bacterial replication and survival. However, the molecular mechanisms by which type III effectors suppress host defense responses are far from being understood. Based on sequence similarity, Xanthomonas outer protein J (XopJ) is a member of the YopJ/AvrRxv family of SUMO peptidases and acetyltranferases, although its biochemical activity has not yet been demonstrated. Confocal laser scanning microscopy revealed that green fluorescent protein (GFP) fusions of XopJ are targeted to the plasma membrane when expressed in plant cells, which most likely involves N-myristoylation. In contrast to a XopJ(C235A) mutant disrupted in the catalytic triad sequence, the wild-type effector GFP fusion protein was also localized in vesicle-like structures colocalizing together with a Golgi marker protein, suggesting an effect of XopJ on vesicle trafficking. To explore an effect of XopJ on protein secretion, we used a GFP-based secretion assay. When a secreted (sec)GFP marker was coexpressed with XopJ in leaves of Nicotiana benthamiana, GFP fluorescence was retained in reticulate structures. In contrast, in plant cells expressing secGFP alone or along with the XopJ(C235A) mutant, no GFP fluorescence accumulated within the cells. Moreover, coexpressing secGFP together with XopJ led to a reduced accumulation of secGFP within the apoplastic fluid of N. benthamiana leaves, further showing that XopJ affects protein secretion. Transgenic expression of XopJ in Arabidopsis suppressed callose deposition elicited by a T3SS-negative mutant of Pseudomonas syringae pv. tomato DC3000. A role of XopJ in the inhibition of cell wall–based defense responses is discussed.

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