scholarly journals Regulation of Biosynthesis of Syringolin A, a Pseudomonas syringae Virulence Factor Targeting the Host Proteasome

2012 ◽  
Vol 25 (9) ◽  
pp. 1198-1208 ◽  
Author(s):  
Christina Ramel ◽  
Nando Baechler ◽  
Michel Hildbrand ◽  
Martin Meyer ◽  
David Schädeli ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Pseudomonas Syringae ◽  
Virulence Factor ◽  
Homoserine Lactone ◽  
Defined Medium ◽  
Lacz Gene ◽  
In Planta ◽  
Phytopathogenic Bacterium ◽  
Promoter Sequences

Many strains of the phytopathogenic bacterium Pseudomonas syringae pv. syringae synthesize the virulence factor syringolin A, which irreversibly inactivates the eukaryotic proteasome. Syringolin A, a peptide derivative, is synthesized by a mixed nonribosomal peptide/polyketide synthetase encoded by five clustered genes, sylA to sylE. Biosynthesis of syringolin A, previously shown to be dependent on the GacS/GacA two-component system, occurs in planta and in vitro but only under still culture conditions in a defined medium. Here, we show that the sylC, sylD, and sylE genes of P. syringae pv. syringae B301D-R form an operon transcribed by promoter sequences located between the sylCDE operon and the sylB gene residing on opposite strands. Assays of overlapping sylB and sylCDE promoter deletions translationally fused to the lacZ gene defined promoter sequences required for gene activity both in vitro and in planta. Activation of both promoters depended on the sylA gene encoding a helix-turn-helix (HTH) LuxR-type transcription factor which was shown to directly bind to the promoters. Activity of the sylA gene, in turn, required a functional salA gene, which also encodes an HTH LuxR-type transcription factor. Furthermore, evidence is presented that acyl-homoserine lactone-mediated quorum-sensing regulation is not involved in syringolin A biosynthesis but that oxygen concentration appears to play a role.

scholarly journals The algT Gene of Pseudomonas syringae pv. glycinea andNew Insights into the Transcriptional Organization of thealgT-muc Gene Cluster

2006 ◽  
Vol 188 (23) ◽  
pp. 8013-8021 ◽  
Author(s):  
Alexander Schenk ◽  
Michael Berger ◽  
Lisa M. Keith ◽  
Carol L. Bender ◽  
Georgi Muskhelishvili ◽  
...  
Keyword(s):  
Gene Cluster ◽  
Pseudomonas Syringae ◽  
Azotobacter Vinelandii ◽  
Regulatory Gene ◽  
In Planta ◽  
Phytopathogenic Bacterium ◽  
Reverse Transcription Pcr ◽  
Alginate Production ◽  
Alginate Biosynthesis

ABSTRACT The phytopathogenic bacterium Pseudomonas syringae pv. glycinea infects soybean plants and causes bacterial blight. In addition to P. syringae, the human pathogen Pseudomonas aeruginosa and the soil bacterium Azotobacter vinelandii produce the exopolysaccharide alginate, a copolymer of d-mannuronic and l-guluronic acids. Alginate production in P. syringae has been associated with increased fitness and virulence in planta. Alginate biosynthesis is tightly controlled by proteins encoded by the algT-muc regulatory gene cluster in P. aeruginosa and A. vinelandii. These genes encode the alternative sigma factor AlgT (σ22), its anti-sigma factors MucA and MucB, MucC, a protein with a controversial function that is absent in P. syringae, and MucD, a periplasmic serine protease and homolog of HtrA in Escherichia coli. We compared an alginate-deficient algT mutant of P. syringae pv. glycinea with an alginate-producing derivative in which algT is intact. The alginate-producing derivative grew significantly slower in vitro growth but showed increased epiphytic fitness and better symptom development in planta. Evaluation of expression levels for algT, mucA, mucB, mucD, and algD, which encodes an alginate biosynthesis gene, showed that mucD transcription is not dependent on AlgT in P. syringae in vitro. Promoter mapping using primer extension experiments confirmed this finding. Results of reverse transcription-PCR demonstrated that algT, mucA, and mucB are cotranscribed as an operon in P. syringae. Northern blot analysis revealed that mucD was expressed as a 1.75-kb monocistronic mRNA in P. syringae.

scholarly journals Zinc phosphate protects tomato plants against Pseudomonas syringae pv. tomato

2021 ◽  
Author(s):  
Mara Quaglia ◽  
Marika Bocchini ◽  
Benedetta Orfei ◽  
Roberto D’Amato ◽  
Franco Famiani ◽  
...  
Keyword(s):  
Disease Severity ◽  
Pseudomonas Syringae ◽  
Zinc Phosphate ◽  
Plant Defence ◽  
In Planta ◽  
Tomato Plants ◽  
Pathogenesis Related Protein ◽  
Defence Responses ◽  
Plant Defence Responses

AbstractThe purpose of this study was to determine whether zinc phosphate treatments of tomato plants (Solanum lycopersicum L.) can attenuate bacterial speck disease severity through reduction of Pseudomonas syringae pv. tomato (Pst) growth in planta and induce morphological and biochemical plant defence responses. Tomato plants were treated with 10 ppm (25.90 µM) zinc phosphate and then spray inoculated with strain DAPP-PG 215, race 0 of Pst. Disease symptoms were recorded as chlorosis and/or necrosis per leaf (%) and as numbers of necrotic spots. Soil treatments with zinc phosphate protected susceptible tomato plants against Pst, with reductions in both disease severity and pathogen growth in planta. The reduction of Pst growth in planta combined with significantly higher zinc levels in zinc-phosphate-treated plants indicated direct antimicrobial toxicity of this microelement, as also confirmed by in vitro assays. Morphological (i.e. callose apposition) and biochemical (i.e., expression of salicylic-acid-dependent pathogenesis-related protein PR1b1 gene) defence responses were induced by the zinc phosphate treatment, as demonstrated by histochemical and qPCR analyses, respectively. In conclusion, soil treatments with zinc phosphate can protect tomato plants against Pst attacks through direct antimicrobial activity and induction of morphological and biochemical plant defence responses.

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

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.

scholarly journals Expression of the ToxA and PtrPf2 genes of the phytopathogenic fungus Pyrenophora tritici-repentis at the beginning of the infection process

2019 ◽  
Author(s):  
Nina V. Mironenko ◽  
Alexandra S. Orina ◽  
Nadezhda M. Kovalenko
Keyword(s):  
Transcription Factor ◽  
Wheat Variety ◽  
Infection Process ◽  
Phytopathogenic Fungus ◽  
In Planta ◽  
Effector Gene ◽  
Pyrenophora Tritici Repentis ◽  
Wheat Leaves ◽  
Necrotrophic Effector

This study shows that the necrotrophic effector gene ToxA is differentially expressed in isolates of P. tritici-repentis fungus at different time periods after inoculation of the wheat variety Glenlea which has the gene Tsn1 controlling sensitivity to the necrosis inducing toxin Ptr ToxA. Two P. tritici-repentis isolates with different ability to cause necrosis on the leaves of Glenlea variety (nec + and nec-) and with different expression level of ToxA and gene of factor transcription PtrPf2 in vitro were used for analysis. Isolates of P. tritici-repentis are characterized by the differential expression of ToxA in planta. The expression of the ToxA gene in P. tritici-repentis ToxA+ isolates significantly increased when infected the wheat leaves compared to ToxA expression results obtained in vitro. The levels of ToxA expression in both isolates differed significantly after 24, 48 and 96 hours after inoculation, however, the dynamics of the trait change over time were similar. However, the highest ToxA expression in the virulent (nec+) isolate in contrast with the avirulent (nec-) isolate was observed at a point of 48 hours. Whereas the expression of regulating transcription factor PtrPf2 in planta differed imperceptibly from expression in vitro throughout the observation period. Obviously, the role of the fungal transcription factor in regulating the effector gene expression weakens in planta, and other mechanisms regulating the expression of pathogen genes at the biotrophic stage of the disease develop.

Novel bacteria degrading N-acylhomoserine lactones and their use as quenchers of quorum-sensing-regulated functions of plant-pathogenic bacteria

Microbiology ◽  
2003 ◽  
Vol 149 (8) ◽  
pp. 1981-1989 ◽  
Author(s):  
Stéphane Uroz ◽  
Cathy D'Angelo-Picard ◽  
Aurélien Carlier ◽  
Miena Elasri ◽  
Carine Sicot ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Pathogenic Bacteria ◽  
Rhodococcus Erythropolis ◽  
Homoserine Lactone ◽  
Signal Molecules ◽  
In Planta ◽  
Signal Molecule ◽  
Violacein Production ◽  
Regulated Functions

Bacteria degrading the quorum-sensing (QS) signal molecule N-hexanoylhomoserine lactone were isolated from a tobacco rhizosphere. Twenty-five isolates degrading this homoserine lactone fell into six groups according to their genomic REP-PCR and rrs PCR-RFLP profiles. Representative strains from each group were identified as members of the genera Pseudomonas, Comamonas, Variovorax and Rhodococcus. All these isolates degraded N-acylhomoserine lactones other than the hexanoic acid derivative, albeit with different specificity and kinetics. One of these isolates, Rhodococcus erythropolis strain W2, was used to quench QS-regulated functions of other microbes. In vitro, W2 strongly interfered with violacein production by Chromobacterium violaceum, and transfer of pathogenicity in Agrobacterium tumefaciens. In planta, R. erythropolis W2 markedly reduced the pathogenicity of Pectobacterium carotovorum subsp. carotovorum in potato tubers. These series of results reveal the diversity of the QS-interfering bacteria in the rhizosphere and demonstrate the validity of targeting QS signal molecules to control pathogens with natural bacterial isolates.

scholarly journals Immunogold Labeling of Hrp Pili of Pseudomonas syringae pv. tomato Assembled in Minimal Medium and In Planta

2001 ◽  
Vol 14 (2) ◽  
pp. 234-241 ◽  
Author(s):  
Wenqi Hu ◽  
Jing Yuan ◽  
Qiao-Ling Jin ◽  
Patrick Hart ◽  
Sheng Yang He
Keyword(s):  
Arabidopsis Thaliana ◽  
Pseudomonas Syringae ◽  
Minimal Medium ◽  
Leaf Tissue ◽  
Hypersensitive Reaction ◽  
Immunogold Labeling ◽  
Structural Protein ◽  
In Planta ◽  
Hrp Genes

Hypersensitive reaction and pathogenicity (hrp) genes are required for Pseudomonas syringae pv. tomato (Pst) DC3000 to cause disease in susceptible tomato and Arabidopsis thaliana plants and to elicit the hypersensitive response in resistant plants. The hrp genes encode a type III protein secretion system known as the Hrp system, which in Pst DC3000 secretes HrpA, HrpZ, HrpW, and AvrPto and assembles a surface appendage, named the Hrp pilus, in hrp-gene-inducing minimal medium. HrpA has been suggested to be the Hrp pilus structural protein on the basis of copurification and mutational analyses. In this study, we show that an antibody against HrpA efficiently labeled Hrp pili, whereas antibodies against HrpW and HrpZ did not. Immunogold labeling of bacteria-infected Arabidopsis thaliana leaf tissue with an Hrp pilus antibody revealed a characteristic lineup of gold particles around bacteria and/or at the bacterium-plant contact site. These results confirm that HrpA is the major structural protein of the Hrp pilus and provide evidence that Hrp pili are assembled in vitro and in planta.

scholarly journals Identification of a putative DNA-binding protein in Arabidopsis that acts as a susceptibility hub and interacts with multiple Pseudomonas syringae effectors

2020 ◽  
Author(s):  
Karl Schreiber ◽  
Jennifer D Lewis
Keyword(s):  
Pseudomonas Syringae ◽  
Transcriptional Profiling ◽  
Effector Proteins ◽  
Ribosomal Protein Genes ◽  
Loss Of Function ◽  
Wild Type ◽  
In Planta ◽  
Arabidopsis Protein ◽  
Wide Range

Phytopathogens use secreted effector proteins to suppress host immunity and promote pathogen virulence, and there is increasing evidence that the host-pathogen interactome comprises a complex network. In an effort to identify novel interactors of the Pseudomonas syringae effector HopZ1a, we performed a yeast two-hybrid screen that identified a previously uncharacterized Arabidopsis protein that we designate HopZ1a Interactor 1 (ZIN1). Additional analyses in yeast and in planta revealed that ZIN1 also interacts with several other P. syringae effectors. We show that an Arabidopsis loss-of-function zin1 mutant is less susceptible to infection by certain strains of P. syringae, while overexpression of ZIN1 results in enhanced susceptibility. Functionally, ZIN1 exhibits topoisomerase-like activity in vitro. Transcriptional profiling of wild-type and zin1 Arabidopsis plants inoculated with P. syringae indicated that while ZIN1 regulates a wide range of pathogen-responsive biological processes, the list of genes more highly expressed in zin1 versus wild-type plants was particularly enriched for ribosomal protein genes. Altogether, these data illuminate ZIN1 as a potential susceptibility hub that interacts with multiple effectors to influence the outcome of plant-microbe interactions.

scholarly journals The ecological genetics ofPseudomonas syringaefrom kiwifruit leaves

2017 ◽  
Author(s):  
Christina Straub ◽  
Elena Colombi ◽  
Li Li ◽  
Hongwen Huang ◽  
Matthew D. Templeton ◽  
...  
Keyword(s):  
Population Structure ◽  
Pseudomonas Syringae ◽  
Bacterial Pathogen ◽  
Ecological Factors ◽  
Ecological Genetics ◽  
Plant Interactions ◽  
In Planta ◽  
Canker Disease ◽  
Pathogen Populations

SUMMARYInteractions between commensal microbes and invading pathogens are understudied, despite their likely effects on pathogen population structure and infection processes. We describe the population structure and genetic diversity of a broad range of co-occurringPseudomonas syringaeisolated from infected and uninfected kiwifruit during an outbreak of bleeding canker disease caused byP. syringaepv.actinidiae(Psa) in New Zealand. Overall population structure was clonal and affected by ecological factors including infection status and cultivar. Most isolates are members of a new clade in phylogroup 3 (PG3a), also present on kiwifruit leaves in China and Japan. Stability of the polymorphism between pathogenicPsaand commensalP. syringaePG3a isolated from the same leaf was tested using reciprocal invasion from rare assaysin vitroand in planta.P. syringaeG33C (PG3a) inhibitedPsaNZ54, while the presence ofPsaNZ54 enhanced the growth ofP. syringaeG33C. This effect could not be attributed to virulence activity encoded by the Type 3 secretion system ofPsa. Together our data contribute toward the development of an ecological perspective on the genetic structure of pathogen populations.ORIGINALITY-SIGNIFICANT STATEMENTBacterial pathogen populations are often studied with little consideration of co-occurring microbes and yet interactions between pathogens and commensals can affect both population structure and disease progression. A fine-scale sampling of commensals present on kiwifruit leaves during an outbreak of bleeding canker disease caused byP. syringaepv.actinidiaereveals a clonal population structure. A new clade of non-pathogenicP. syringae(PG3a) appears to be associated with kiwifruit on a global scale. The presence of PG3a on kiwifruit has significant effects on the outcome of infection byP. syringaepv.actinidiae. This emphasises the value of studying the effect of co-occurring bacteria on pathogen-plant interactions.

scholarly journals Ralstonia solanacearum Needs Flp Pili for Virulence on Potato

2012 ◽  
Vol 25 (4) ◽  
pp. 546-556 ◽  
Author(s):  
Charles K. Wairuri ◽  
Jacquie E. van der Waals ◽  
Antoinette van Schalkwyk ◽  
Jacques Theron
Keyword(s):  
Ralstonia Solanacearum ◽  
Type Iv Pili ◽  
Periodontal Pathogen ◽  
Wild Type ◽  
In Planta ◽  
Phytopathogenic Bacterium ◽  
Type Iv ◽  
Plant Pathogenesis

Type IV pili are virulence factors in various bacteria. Several subclasses of type IV pili have been described according to the characteristics of the structural prepilin subunit. Although type IVa pili have been implicated in the virulence of Ralstonia solanacearum, type IVb pili have not previously been described in this plant pathogen. Here, we report the characterization of two distinct tad loci in the R. solanacearum genome. The tad genes encode functions necessary for biogenesis of the Flp subfamily of type IVb pili initially described for the periodontal pathogen Aggregatibacter actinomycetemcomitans. To determine the role of the tad loci in R. solanacearum virulence, we mutated the tadA2 gene located in the megaplasmid that encodes a predicted NTPase previously reported to function as the energizer for Flp pilus biogenesis. Characterization of the tadA2 mutant revealed that it was not growth impaired in vitro or in planta, produced wild-type levels of exopolysaccharide galactosamine, and exhibited swimming and twitching motility comparable with the wild-type strain. However, the tadA2 mutant was impaired in its ability to cause wilting of potato plants. This is the first report where type IVb pili in a phytopathogenic bacterium contribute significantly to plant pathogenesis.

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