scholarly journals Molecular defense responses of apple genotypes in compatible and incompatible interactions with Erwinia amylovora

2002 ◽  
Vol 38 (SI 1 - 6th Conf EFPP 2002) ◽  
pp. S139-S140
Author(s):  
M.N. Brisset ◽  
J.S. Venisse ◽  
J.P. Paulin
Keyword(s):  
Pseudomonas Syringae ◽  
Type Strain ◽  
Fire Blight ◽  
Molecular Mechanisms ◽  
Erwinia Amylovora ◽  
Wild Type Strain ◽  
Defense Responses ◽  
Bacterial Disease ◽  
Wild Type ◽  
Susceptible Host

Erwinia amylovora is the causal agent of fire blight, a bacterial disease of apple and pear. Pathogenicity determinants of the bacteria are identified (hrp-dsp cluster, capsule, siderophore) but molecular mechanisms leading to susceptibility or resistance of the plant are not yet understood. To address this question, we challenged two genotypes of apple, known for their contrasting susceptibility to fire blight, with a wild-type strain of E. amylovora (Ea wt), an avirulent hrp mutant of this bacteria (Ea hrp) or a wild-type strain of the incompatible pathogen Pseudomonas syringae pv. tabaci (Pst wt). Mechanisms usually related to resistance responses were investigated i.e. oxidative stress, accumulation of PR-proteins and induction of genes encoding various enzymes of the phenylpropanoid pathway. Results showed two kinds of responses (i) some mechanisms were elicited in both susceptible and resistant genotypes by Ea wt and Pst wt with similar kinetics and not induced by Ea hrp, (ii) others were specifically repressed by Ea wt in its susceptible host, when induced by Pst wt and Ea hrp. These results suggest several hypothesis about the cross-talk between E. amylovora and its host plants.

scholarly journals Quorum Sensing Regulates Exopolysaccharide Production, Motility, and Virulence in Pseudomonas syringae

2005 ◽  
Vol 18 (7) ◽  
pp. 682-693 ◽  
Author(s):  
Beatriz Quiñones ◽  
Glenn Dulla ◽  
Steven E. Lindow
Keyword(s):  
Quorum Sensing ◽  
Pseudomonas Syringae ◽  
Type Strain ◽  
Double Mutant ◽  
Wild Type Strain ◽  
Homoserine Lactone ◽  
Brown Spot ◽  
Wild Type ◽  
In Planta ◽  
Alginate Production

The N-acyl homoserine lactone (AHL)-mediated quorumsensing system in the phytopathogen Pseudomonas syringae pv. syringae requires the AHL synthase AhlI and the regulator AhlR, and is additionally subject to regulation by AefR. The contribution of quorum sensing to the expression of a variety of traits expected to be involved in epiphytic fitness and virulence of P. syringae were examined. Both an aefR- mutant and an ahlR- double mutant, deficient in AHL production, were significantly impaired in alginate production and had an increased susceptibility to hydrogen peroxide compared with the wild-type strain. These mutants were hypermotile in culture, invaded leaves more rapidly, and caused an increased incidence of brown spot lesions on bean leaves after a 48-h moist incubation. Interestingly, an aefR- mutant was both the most motile and virulent. Like the wild-type strain, the AHL-deficient mutant strains incited water-soaked lesions on bean pods. However, lesions caused by an ahlI- ahlR- double mutant were larger, whereas those incited by an aefR- mutant were smaller. In contrast, tissue maceration of pods, which occurs at a later stage of infection, was completely abolished in the AHL-deficient mutants. Both the incidence of disease and in planta growth of P. syringae pv. tabaci were greatly reduced in transgenic tobacco plants that produced AHL compared with wild-type plants. These results demonstrate that quorum sensing in P. syringae regulates traits that contribute to epiphytic fitness as well as to distinct stages of disease development during plant infection.

scholarly journals The Type III Secretion Chaperone HpaB Controls the Translocation of Effector and Noneffector Proteins From Xanthomonas campestris pv. vesicatoria

2018 ◽  
Vol 31 (1) ◽  
pp. 61-74 ◽  
Author(s):  
Felix Scheibner ◽  
Nadine Hartmann ◽  
Jens Hausner ◽  
Christian Lorenz ◽  
Anne-Katrin Hoffmeister ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
Type Strain ◽  
Xanthomonas Campestris ◽  
Molecular Mechanisms ◽  
Wild Type Strain ◽  
Effector Proteins ◽  
Wild Type ◽  
Type Iii ◽  
In The Wild ◽  
Secretion Chaperone

Pathogenicity of the gram-negative bacterium Xanthomonas campestris pv. vesicatoria depends on a type III secretion (T3S) system, which translocates effector proteins into plant cells. Effector proteins contain N-terminal T3S and translocation signals and interact with the T3S chaperone HpaB, which presumably escorts effectors to the secretion apparatus. The molecular mechanisms underlying the recognition of effectors by the T3S system are not yet understood. In the present study, we analyzed T3S and translocation signals in the type III effectors XopE2 and XopJ from X. campestris pv. vesicatoria. Both effectors contain minimal translocation signals, which are only recognized in the absence of HpaB. Additional N-terminal signals promote translocation of XopE2 and XopJ in the wild-type strain. The results of translocation and interaction studies revealed that the interaction of XopE2 and XopJ with HpaB and a predicted cytoplasmic substrate docking site of the T3S system is not sufficient for translocation. In agreement with this finding, we show that the presence of an artificial HpaB-binding site does not promote translocation of the noneffector XopA in the wild-type strain. Our data, therefore, suggest that the T3S chaperone HpaB not only acts as an escort protein but also controls the recognition of translocation signals.

scholarly journals The Role of Ethylene Production in Virulence of Pseudomonas syringae pvs. glycinea and phaseolicola

2001 ◽  
Vol 91 (5) ◽  
pp. 511-518 ◽  
Author(s):  
Helge Weingart ◽  
Henriette Ullrich ◽  
Klaus Geider ◽  
Beate Völksch
Keyword(s):  
Pseudomonas Syringae ◽  
Ethylene Production ◽  
Type Strain ◽  
Wild Type Strain ◽  
Wild Type ◽  
In Planta ◽  
Population Sizes ◽  
Soybean Plants ◽  
Type Strains

The importance of ethylene production for virulence of Pseudomonas syringae pvs. glycinea and phaseolicola was assayed by comparing bacterial multiplication and symptom development in bean and soybean plants inoculated with ethylene-negative (efe) mutants and wild-type strains. The efe mutants of Pseudomonas syringae pv. glycinea were significantly reduced in their ability to grow in planta. However, the degree of reduction was strain-dependent. Population sizes of efe mutant 16/83-E1 that did not produce the phototoxin coronatine were 10- and 15-fold lower than those of the wild-type strain on soybean and on bean, and 16/83-E1 produced very weak symptoms compared with the wild-type strain. The coronatine-producing efe mutant 7a/90-E1 reached fourfold and twofold lower population sizes compared with the wild-type strain on soybean and bean, respectively, and caused disease symptoms typical of the wild-type strain. Experiments with ethylene-insensitive soybeans confirmed these results. The virulence of the wild-type strains was reduced to the same extent in ethylene-insensitive soybean plants as the virulence of the efe mutants in ethylene-susceptible soybeans. In contrast, the virulence of Pseudomonas syringae pv. phaseolicola was not affected by disruption of the efe gene.

scholarly journals Dual Role of Desferrioxamine in Erwinia amylovora Pathogenicity

1998 ◽  
Vol 11 (8) ◽  
pp. 734-742 ◽  
Author(s):  
Alia Dellagi ◽  
Marie-Noëlle Brisset ◽  
Jean-Pierre Paulin ◽  
Dominique Expert
Keyword(s):  
Electrolyte Leakage ◽  
Type Strain ◽  
Insertional Mutagenesis ◽  
Erwinia Amylovora ◽  
Wild Type Strain ◽  
Wild Type ◽  
Transport Pathway ◽  
Critical Function ◽  
Necrotic Symptom

To investigate the role of iron in Erwinia amylovora pathogenicity, virulence properties of two mutants of strain CFBP 1430 isolated by insertional mutagenesis and affected in the iron transport pathway mediated by desferrioxamine (DFO) were analyzed. One mutation (dfoA∷MudIIpR13) disrupts DFO biosynthesis. The present analysis shows that this mutation affects an open reading frame that belongs to a biosynthetic gene cluster and shares identity with the alcA gene required for synthesis of the siderophore alcaligin in Bordetella spp. A second mutation (foxR∷MudIIpR13) affects the synthesis of the ferrioxamine receptor FoxR, encoded by the foxR gene, and was shown to be transcribed into a monocistronic message. Accordingly, the foxR mutant accumulates DFO in the external medium. The growth of the mutants when supplied with various iron sources was examined; it indicates that the production of DFO and the specific transport of the DFO ferric complex are required only when iron is strongly liganded. Pathogenicity was scored after inoculation of apple seedlings and after infection of apple flowers. On seedlings, the DFO biosynthetic mutant behaved like the wild-type strain while the frequency of necrotic plants caused by the receptor mutant decreased by a factor of two to five, depending on the initial inoculum. On flowers, both mutants were strongly affected in their ability to initiate a necrotic symptom and their growth was reduced by two orders of magnitude relative to the wild-type strain. However, the virulence of the dfoA mutant varied with the inoculum concentration. Unlike the foxR mutant, the dfoA mutant only weakly induced plant cell electrolyte leakage in tobacco leaf disks. The supply with exogenous DFO, only when iron free, restored the ability to induce electrolyte leakage to the dfoA mutant and increased the leakage induced by other strains. DFO alone was not an inducer. Iron-free DFO was able to protect E. amylovora cells against lethal doses of hydrogen peroxide. The main conclusion was that production of DFO in E. amylovora during pathogenesis is not only a critical function for iron acquisition, but can play a role in the oxidative burst elicited by the bacteria.

scholarly journals The In Planta-Produced Extracellular Proteins ECP1 and ECP2 of Cladosporium fulvum Are Virulence Factors

1997 ◽  
Vol 10 (6) ◽  
pp. 725-734 ◽  
Author(s):  
Richard Laugé ◽  
Matthieu H. A. J. Joosten ◽  
Guido F. J. M. Van den Ackerveken ◽  
Henk W. J. Van den Broek ◽  
Pierre J. G. M. De Wit
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Pathogenic Fungus ◽  
Leaf Tissue ◽  
Defense Responses ◽  
Gene Replacement ◽  
Extracellular Proteins ◽  
Cladosporium Fulvum ◽  
Wild Type ◽  
In Planta

The two extracellular proteins ECP1 and ECP2 are abundantly secreted by the plant-pathogenic fungus Cladosporium fulvum during colonization of the intercellular space of tomato leaves. We examined the involvement of both proteins in pathogenicity and virulence of this fungus. ECP1-deficient, ECP2-deficient, and ECP1/ECP2- deficient isogenic C. fulvum strains were created by targeted gene replacement. Upon inoculation onto susceptible 6-week-old tomato plants, all three mutants showed reduced virulence. Deficiency in ECP2 resulted in a strain that poorly colonized the leaf tissue and secreted lower amounts of the in planta-produced ECP3, AVR4, and AVR9 proteins than the wild-type strain. The ECP2-deficient strain produced little emerging mycelium and few conidia. Deficiency in ECP1 did not significantly modify colonization of the leaf tissue, but reduced secretion of in planta-produced proteins. The ECP1-deficient strain emerged from stomata of the lower epidermis, but failed to sporulate as abundantly as the wild-type strain. A strain deficient in both ECP1 and ECP2 proteins had a phenotype similar to that of the ECP2-deficient strain. Accumulation of pathogenesis-related proteins and induction of late responses, such as leaf desiccation and abscission, occurred more quickly and more severely in tomato after inoculation with the ECP1-, ECP2-, and ECP1/ECP2-deficient strains than after inoculation with the wild-type strain. Moreover, partial collapse of stomatal guard cells occurred at emergence of the ECP2-deficient strain. These results indicate that the ECP1 and ECP2 proteins play a role in virulence of C. fulvum on tomato and suggest that both are involved in suppression of host defense responses.

scholarly journals Fumarate-Mediated Persistence of Escherichia coli against Antibiotics

2016 ◽  
Vol 60 (4) ◽  
pp. 2232-2240 ◽  
Author(s):  
Jun-Seob Kim ◽  
Da-Hyeong Cho ◽  
Paul Heo ◽  
Suk-Chae Jung ◽  
Myungseo Park ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Type Strain ◽  
Molecular Mechanisms ◽  
Wild Type Strain ◽  
Wild Type ◽  
Content Type ◽  
E Coli ◽  
Quiescent Cells ◽  
Transport Chain ◽  
Genetic Perturbations

ABSTRACTBacterial persisters are a small fraction of quiescent cells that survive in the presence of lethal concentrations of antibiotics. They can regrow to give rise to a new population that has the same vulnerability to the antibiotics as did the parental population. Although formation of bacterial persisters in the presence of various antibiotics has been documented, the molecular mechanisms by which these persisters tolerate the antibiotics are still controversial. We found that amplification of the fumarate reductase operon (FRD) inEscherichia coliled to a higher frequency of persister formation. The persister frequency ofE. coliwas increased when the cells contained elevated levels of intracellular fumarate. Genetic perturbations of the electron transport chain (ETC), a metabolite supplementation assay, and even the toxin-antitoxin-relatedhipA7mutation indicated that surplus fumarate markedly elevated theE. colipersister frequency. AnE. colistrain lacking succinate dehydrogenase (SDH), thereby showing a lower intracellular fumarate concentration, was killed ∼1,000-fold more effectively than the wild-type strain in the stationary phase. It appears thatSDHandFRDrepresent a paired system that gives rise to and maintainsE. colipersisters by producing and utilizing fumarate, respectively.

scholarly journals Two-Component Sensor RhpS Promotes Induction of Pseudomonas syringae Type III Secretion System by Repressing Negative Regulator RhpR

2007 ◽  
Vol 20 (3) ◽  
pp. 223-234 ◽  
Author(s):  
Yanmei Xiao ◽  
Lefu Lan ◽  
Chuntao Yin ◽  
Xin Deng ◽  
Douglas Baker ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Type Iii Secretion ◽  
Type Strain ◽  
Wild Type Strain ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Deletion Strain ◽  
Wild Type ◽  
Two Component ◽  
In The Wild

The Pseudomonas syringae type III secretion system (T3SS) is induced during interaction with the plant or culture in minimal medium (MM). How the bacterium senses these environments to activate the T3SS is poorly understood. Here, we report the identification of a novel two-component system (TCS), RhpRS, that regulates the induction of P. syringae T3SS genes. The rhpR and rhpS genes are organized in an operon with rhpR encoding a putative TCS response regulator and rhpS encoding a putative biphasic sensor kinase. Transposon insertion in rhpS severely reduced the induction of P. syringae T3SS genes in the plant as well as in MM and significantly compromised the pathogenicity on host plants and hypersensitive response-inducing activity on nonhost plants. However, deletion of the rhpRS locus allowed the induction of T3SS genes to the same level as in the wild-type strain and the recovery of pathogenicity upon infiltration into plants. Overexpression of RhpR in the ΔrhpRS deletion strain abolished the induction of T3SS genes. However, overexpression of RhpR in the wild-type strain or overexpression of RhpR(D70A), a mutant of the predicted phosphorylation site of RhpR, in the ΔrhpRS deletion strain only slightly reduced the induction of T3SS genes. Based on these results, we propose that the phosphorylated RhpR represses the induction of T3SS genes and that RhpS reverses phosphorylation of RhpR under the T3SS-inducing conditions. Epistasis analysis indicated that rhpS and rhpR act upstream of hrpR to regulate T3SS genes.

scholarly journals Influence of the Plant Defense Response to Escherichia coli O157:H7 Cell Surface Structures on Survival of That Enteric Pathogen on Plant Surfaces

2012 ◽  
Vol 78 (16) ◽  
pp. 5882-5889 ◽  
Author(s):  
Suengwook Seo ◽  
Karl R. Matthews
Keyword(s):  
Cell Surface ◽  
Plant Defense ◽  
Type Strain ◽  
Wild Type Strain ◽  
Defense Responses ◽  
Surface Structures ◽  
Wild Type ◽  
Content Type ◽  
E Coli ◽  
Cell Surface Structures

ABSTRACTConsumption of fresh and fresh-cut fruits and vegetables contaminated withEscherichia coliO157:H7 has resulted in hundreds of cases of illness and, in some instances, death. In this study, the influence of cell surface structures ofE. coliO157:H7, such as flagella, curli fimbriae, lipopolysaccharides, or exopolysaccharides, on plant defense responses and on survival or colonization on the plant was investigated. The population of theE. coliO157:H7 ATCC 43895 wild-type strain was significantly lower on wild-typeArabidopsisplants than that of the 43895 flagellum-deficient mutant. The population of theE. coliO157:H7 43895 flagellum mutant was greater on both wild-type andnpr1-1mutant (nonexpressor of pathogenesis-related [PR] genes) plants and resulted in less PR gene induction, estimated based on a weak β-glucuronidase (GUS) signal, than did the 43895 wild-type strain. These results suggest that the flagella, among the other pathogen-associated molecular patterns (PAMPs), made a substantial contribution to the induction of plant defense response and contributed to the decreased numbers of theE. coliO157:H7 ATCC 43895 wild-type strain on the wild-typeArabidopsisplant. A curli-deficientE. coliO157:H7 86-24 strain survived better on wild-typeArabidopsisplants than the curli-producing wild-type 86-24 strain did. The curli-deficientE. coliO157:H7 86-24 strain exhibited a GUS signal at a level substantially lower than that of the curli-producing wild-type strain. Curli were recognized by plant defense systems, consequently affecting bacterial survival. The cell surface structures ofE. coliO157:H7 have a significant impact on the induction of differential plant defense responses, thereby impacting persistence or survival of the pathogen on plants.

scholarly journals Analysis of the small RNA spf in the plant pathogen Pseudomonas syringae pv. tomato strain DC3000

Microbiology ◽  
2014 ◽  
Vol 160 (5) ◽  
pp. 941-953 ◽  
Author(s):  
So Hae Park ◽  
Zhongmeng Bao ◽  
Bronwyn G. Butcher ◽  
Katherine D’Amico ◽  
Yun Xu ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Type Strain ◽  
Wild Type Strain ◽  
Comparative Genomic ◽  
Wild Type ◽  
New Information ◽  
Genomic Analyses ◽  
Increased Sensitivity ◽  
Non Coding Rnas

Bacteria contain small non-coding RNAs (ncRNAs) that are typically responsible for altering transcription, translation or mRNA stability. ncRNAs are important because they often regulate virulence factors and susceptibility to various stresses. Here, the regulation of a recently described ncRNA of Pseudomonas syringae DC3000, spot 42 (now referred to as spf), was investigated. A putative RpoE binding site was identified upstream of spf in strain DC3000. RpoE is shown to regulate the expression of spf. Also, deletion of spf results in increased sensitivity to hydrogen peroxide compared with the wild-type strain, suggesting that spf plays a role in susceptibility to oxidative stress. Furthermore, expression of alg8 is shown to be influenced by spf, suggesting that this ncRNA plays a role in alginate biosynthesis. Structural and comparative genomic analyses show this ncRNA is well conserved among the pseudomonads. The findings provide new information on the regulation and role of this ncRNA in P. syringae.

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