scholarly journals The Erwinia amylovora avrRpt2EA Gene Contributes to Virulence on Pear and AvrRpt2EA Is Recognized by Arabidopsis RPS2 When Expressed in Pseudomonas syringae

2006 ◽  
Vol 19 (6) ◽  
pp. 644-654 ◽  
Author(s):  
Youfu Zhao ◽  
Sheng-Yang He ◽  
George W. Sundin
Keyword(s):  
Pseudomonas Syringae ◽  
Erwinia Amylovora ◽  
Signal Sequence ◽  
Systemic Infection ◽  
Disease Resistance Gene ◽  
Functional Domain ◽  
Tomato Dc3000 ◽  
Native Form ◽  
Specific Regulation ◽  
Blight Disease

The enterobacterium Erwinia amylovora is a devastating plant pathogen causing necrotrophic fire blight disease of apple, pear, and other rosaceous plants. In an attempt to identify genes induced during infection of host plants, we identified and cloned a putative effector gene,avrRpt2EA. The deduced amino-acid sequence of the translated AvrRpt2EA protein is homologous to the effector protein AvrRpt2 previously reported in Pseudomonas syringae pv. tomato. These two proteins share 58% identity (70% similarity) in the functional domain; however, the secretion and translocation signal domain varied. The avrRpt2EA promoter region contains a typical ‘hrp box,’ which suggests that avrRpt2EA is regulated by the alternative sigma factor, HrpL. avrRpt2EA was detected in all E. amylovora strains tested but not in other closely related Erwinia species. An avrRpt2EA deletion mutant was reduced in its ability to cause systemic infection on immature pear fruits as compared with the wild-type strain, indicating that avrRpt2EA acts as a virulence factor on its native host. Growth of P. syringae pv. tomato DC3000 expressing avrRpt2EA was 10-fold higher than that of P. syringae pv. tomato DC3000 in an Arabidopsis rps2 mutant, indicating that avrRpt2EA promotes virulence of P. syringae pv. tomato DC3000 on Arabi-dopsis similar to P. syringae pv. tomato avrRpt2. When avrRpt2EA was expressed in P. syringae pv. tomato DC3000 in its native form, a weak hypersensitive response (HR) was induced in Arabidopsis; however, a hybrid protein containing the P. syringae pv. tomato avrRpt2 signal sequence, when expressed from the P. syringae pv. tomato avrRpt2 promoter, caused a strong HR. Thus, the signal sequence and promoter of avrRpt2EA may affect its expression, secretion, or translocation, singly or in combination, in P. syringae pv. tomato DC3000. These results indicated that avrRpt2EA is genetically recognized by the RPS2 disease resistance gene in Arabidopsis when expressed in P. syringae pv. tomato DC3000. The results also suggested that although distinct pathogens such as E. amylovora and P. syringae may contain similar effector genes, expression and secretion of these effectors can be under specific regulation by the native pathogen.

scholarly journals Identification of Erwinia amylovora Genes Induced during Infection of Immature Pear Tissue

2005 ◽  
Vol 187 (23) ◽  
pp. 8088-8103 ◽  
Author(s):  
Youfu Zhao ◽  
Sara E. Blumer ◽  
George W. Sundin
Keyword(s):  
Pseudomonas Syringae ◽  
Erwinia Amylovora ◽  
Sequence Similarity ◽  
Type Ii Secretion ◽  
Knockout Mutant ◽  
Technology System ◽  
Microbe Interactions ◽  
Host Microbe Interactions ◽  
Blight Disease

ABSTRACT The enterobacterium Erwinia amylovora is a devastating plant pathogen causing necrotrophic fire blight disease of apple, pear, and other rosaceous plants. In this study, we used a modified in vivo expression technology system to identify E. amylovora genes that are activated during infection of immature pear tissue, a process that requires the major pathogenicity factors of this organism. We identified 394 unique pear fruit-induced (pfi) genes on the basis of sequence similarity to known genes and separated them into nine putative function groups including host-microbe interactions (3.8%), stress response (5.3%), regulation (11.9%), cell surface (8.9%), transport (13.5%), mobile elements (1.0%), metabolism (20.3%), nutrient acquisition and synthesis (15.5%), and unknown or hypothetical proteins (19.8%). Known virulence genes, including hrp/hrc components of the type III secretion system, the major effector gene dspE, type II secretion, levansucrase (lsc), and regulators of levansucrase and amylovoran biosynthesis, were upregulated during pear tissue infection. Known virulence factors previously identified in E. (Pectobacterium) carotovora and Pseudomonas syringae were identified for the first time in E. amylovora and included HecA hemagglutinin family adhesion, Peh polygalacturonase, new effector HopPtoCEA, and membrane-bound lytic murein transglycosylase MltEEA. An insertional mutation within hopPtoC EA did not result in reduced virulence; however, an mltE EA knockout mutant was reduced in virulence and growth in immature pears. This study suggests that E. amylovora utilizes a variety of strategies during plant infection and to overcome the stressful and poor nutritional environment of its plant hosts.

scholarly journals Identification of Three Putative Signal Transduction Genes Involved in R Gene-Specified Disease Resistance in Arabidopsis

Genetics ◽  
1999 ◽  
Vol 152 (1) ◽  
pp. 401-412 ◽  
Author(s):  
Randall F Warren ◽  
Peter M Merritt ◽  
Eric Holub ◽  
Roger W Innes
Keyword(s):  
Disease Resistance ◽  
Pseudomonas Syringae ◽  
Resistance Genes ◽  
Virulent Strain ◽  
Disease Resistance Genes ◽  
Avirulence Gene ◽  
Detectable Effect ◽  
Disease Resistance Gene ◽  
Protein Functions ◽  
Signal Transduction Genes

Abstract The RPS5 disease resistance gene of Arabidopsis mediates recognition of Pseudomonas syringae strains that possess the avirulence gene avrPphB. By screening for loss of RPS5-specified resistance, we identified five pbs (avrPphB susceptible) mutants that represent three different genes. Mutations in PBS1 completely blocked RPS5-mediated resistance, but had little to no effect on resistance specified by other disease resistance genes, suggesting that PBS1 facilitates recognition of the avrPphB protein. The pbs2 mutation dramatically reduced resistance mediated by the RPS5 and RPM1 resistance genes, but had no detectable effect on resistance mediated by RPS4 and had an intermediate effect on RPS2-mediated resistance. The pbs2 mutation also had varying effects on resistance mediated by seven different RPP (recognition of Peronospora parasitica) genes. These data indicate that the PBS2 protein functions in a pathway that is important only to a subset of disease-resistance genes. The pbs3 mutation partially suppressed all four P. syringae-resistance genes (RPS5, RPM1, RPS2, and RPS4), and it had weak-to-intermediate effects on the RPP genes. In addition, the pbs3 mutant allowed higher bacterial growth in response to a virulent strain of P. syringae, indicating that the PBS3 gene product functions in a pathway involved in restricting the spread of both virulent and avirulent pathogens. The pbs mutations are recessive and have been mapped to chromosomes I (pbs2) and V (pbs1 and pbs3).

The hrp pathogenicity island of Pseudomonas syringae pv. tomato DC3000 is induced by plant phenolic acids

2015 ◽  
Vol 53 (10) ◽  
pp. 725-731 ◽  
Author(s):  
Jun Seung Lee ◽  
Hye Ryun Ryu ◽  
Ji Young Cha ◽  
Hyung Suk Baik
Keyword(s):  
Pseudomonas Syringae ◽  
Phenolic Acids ◽  
Pathogenicity Island ◽  
Tomato Dc3000

scholarly journals The AGA1 product is involved in cell surface attachment of the Saccharomyces cerevisiae cell adhesion glycoprotein a-agglutinin.

1991 ◽  
Vol 11 (8) ◽  
pp. 4196-4206 ◽  
Author(s):  
A Roy ◽  
C F Lu ◽  
D L Marykwas ◽  
P N Lipke ◽  
J Kurjan
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Surface ◽  
Signal Sequence ◽  
Complementation Group ◽  
Alpha Cells ◽  
Specific Expression ◽  
Surface Attachment ◽  
Cellular Aggregation ◽  
Specific Regulation ◽  
Binding Subunit

Saccharomyces cerevisiae a and alpha cells express the complementary cell surface glycoproteins a-agglutinin and alpha-agglutinin, respectively, which interact with one another to promote cellular aggregation during mating. Treatment of S. cerevisiae a cells with reducing agents releases the binding subunit of a-agglutinin, which has been purified and characterized; little biochemical information on the overall structure of a-agglutinin is available. To characterise a-agglutinin structure and function, we have used a genetic approach to clone an a-agglutinin structural gene (AGAI). Mutants with a-specific agglutination defects were isolated, the majority of which fell into a single complementation group, called aga1. The aga1 mutants showed wild-type pheromone production and response, efficient mating on solid medium, and a mating defect in liquid medium; these phenotypes are characteristic of agglutinin mutants. The AGA1 gene was cloned by complementation; the gene sequence indicated that it could encode a protein of 725 amino acids with high serine and threonine content, a putative N-terminal signal sequence, and a C-terminal hydrophobic sequence similar to signals for the attachment to glycosyl phosphatidylinositol anchors. Active a-agglutinin binding subunit is secreted by aga1 mutants, indicating that AGA1 is involved in cells surface attachment of a-agglutinin. This result suggests that AGA1 encodes a protein with functional similarity to the core subunits of a-agglutinin analogs from other budding yeasts. Unexpectedly, the AGA1 transcript was expressed and induced by pheromone in both a and alpha cells, suggesting that the a-specific expression of active a-agglutinin results only from a-specific regulation of the a-agglutinin binding subunit.

scholarly journals A Draft Genome Sequence of Pseudomonas syringae pv. tomato T1 Reveals a Type III Effector Repertoire Significantly Divergent from That of Pseudomonas syringae pv. tomato DC3000

2009 ◽  
Vol 22 (1) ◽  
pp. 52-62 ◽  
Author(s):  
Nalvo F. Almeida ◽  
Shuangchun Yan ◽  
Magdalen Lindeberg ◽  
David J. Studholme ◽  
David J. Schneider ◽  
...  
Keyword(s):  
Host Range ◽  
Host Specificity ◽  
Pseudomonas Syringae ◽  
Genome Sequence ◽  
Draft Genome ◽  
Draft Genome Sequence ◽  
Tomato Dc3000 ◽  
Type Iii ◽  
Host Range Determination ◽  
Range Determination

Diverse gene products including phytotoxins, pathogen-associated molecular patterns, and type III secreted effectors influence interactions between Pseudomonas syringae strains and plants, with additional yet uncharacterized factors likely contributing as well. Of particular interest are those interactions governing pathogen-host specificity. Comparative genomics of closely related pathogens with different host specificity represents an excellent approach for identification of genes contributing to host-range determination. A draft genome sequence of Pseudomonas syringae pv. tomato T1, which is pathogenic on tomato but nonpathogenic on Arabidopsis thaliana, was obtained for this purpose and compared with the genome of the closely related A. thaliana and tomato model pathogen P. syringae pv. tomato DC3000. Although the overall genetic content of each of the two genomes appears to be highly similar, the repertoire of effectors was found to diverge significantly. Several P. syringae pv. tomato T1 effectors absent from strain DC3000 were confirmed to be translocated into plants, with the well-studied effector AvrRpt2 representing a likely candidate for host-range determination. However, the presence of avrRpt2 was not found sufficient to explain A. thaliana resistance to P. syringae pv. tomato T1, suggesting that other effectors and possibly type III secretion system–independent factors also play a role in this interaction.

scholarly journals Overexpression of Pto Induces a Salicylate-Independent Cell Death But Inhibits Necrotic Lesions Caused by Salicylate-Deficiency in Tomato Plants

2002 ◽  
Vol 15 (7) ◽  
pp. 654-661 ◽  
Author(s):  
Jianxiong Li ◽  
Libo Shan ◽  
Jian-Min Zhou ◽  
Xiaoyan Tang
Keyword(s):  
Cell Death ◽  
Disease Resistance ◽  
Pseudomonas Syringae ◽  
Virulent Strain ◽  
Gene Activation ◽  
Cellular Damage ◽  
Minor Role ◽  
Disease Resistance Gene ◽  
Tomato Plants ◽  
Spontaneous Cell Death

Tomato plants overexpressing the disease resistance gene Pto (35S∷Pto) exhibit spontaneous cell death, accumulation of salicylic acid (SA), elevated expression of pathogenesis-related genes, and enhanced resistance to a broad range of pathogens. Because salicylate plays an important role in the cell death and defense activation in many lesion mimic mutants, we investigated the interaction of SA-mediated processes and the 35S∷Pto-mediated defense pathway by introducing the nahG transgene that encodes salicylate hydroxylase. Here, we show that SA is not required for the 35S∷Pto-activated microscopic cell death and plays a minor role in defense gene activation and general disease resistance in 35S∷Pto plants. In contrast, temperature greatly affects the spontaneous cell death and general resistance in 35S∷Pto plants, and high temperature inhibits the cell death. The NahG tomato plants develop spontaneous, unconstrained necrotic lesions on leaves. These lesions also are initiated by the inoculation of a virulent strain of Pseudomonas syringae pv. tomato. However, the NahG-dependent necrotic lesions are inhibited in the NahG/35S∷Pto plants. This inhibition is most pronounced under conditions favoring the 35S∷Pto-mediated spontaneous cell death development. These results indicate that the signaling pathways activated by Pto overexpression suppress the cellular damage that is caused by SA depletion. We also found that ethylene is dispensable for the 35S∷Pto-mediated general defense.

scholarly journals Conversion of a class II integral membrane protein into a soluble and efficiently secreted protein: multiple intracellular and extracellular oligomeric and conformational forms.

1990 ◽  
Vol 110 (4) ◽  
pp. 999-1011 ◽  
Author(s):  
R G Paterson ◽  
R A Lamb
Keyword(s):  
Monoclonal Antibodies ◽  
Membrane Protein ◽  
Signal Sequence ◽  
Integral Membrane Protein ◽  
Signal Peptidase ◽  
Protein Fusion ◽  
Native Form ◽  
Hydrophobic Domain ◽  
External Domain ◽  
Signal Anchor

The NH2 terminus of the F1 subunit of the paramyxovirus SV5 fusion protein (fusion related external domain; FRED) is a hydrophobic domain that is implicated as being involved in mediating membrane fusion. We have examined the ability of the FRED to function as a combined signal/anchor domain by substituting it for the natural NH2-terminal signal/anchor domain of a model type II integral membrane protein: the hybrid protein (NAF) was expressed in eukaryotic cells. The FRED was shown to act as a signal sequence, targeting NAF to the lumen of the ER, by the fact that NAF acquired N-linked carbohydrate chains. Alkali fractionation of microsomes indicated that NAF is a soluble protein in the lumen of the ER, and the results of NH2-terminal sequence analysis showed that the FRED is cleaved at a site predicted to be recognized by signal peptidase. NAF was found to be efficiently secreted (t1/2 approximately 90 min) from the cell. By using a combination of sedimentation velocity centrifugation and immunoprecipitation assays using polyclonal and conformation-specific monoclonal antibodies it was found that extracellular NAF consisted of a mixture of monomers, disulfide-linked dimers, and tetramers. The majority of the extracellular NAF molecules were not reactive with the conformation-specific monoclonal antibodies, suggesting they were not folded in a native form and that only the NAF tetramers had matured to a native conformation such that they exhibited NA activity. The available data indicate that NAF is transported intracellularly in multiple oligomeric and conformational forms.

scholarly journals Evaluation of Susceptibility of Different Pear Hybrid Populations to Fire Blight (Erwinia amylovora)

2011 ◽  
Vol 39 (1) ◽  
pp. 226 ◽  
Author(s):  
Yasemin EVRENOSOĞLU ◽  
Adalet MISIRLI ◽  
Hikmet SAYGILI ◽  
Emre BİLEN ◽  
Özlem BOZTEPE ◽  
...  
Keyword(s):  
Fire Blight ◽  
Erwinia Amylovora ◽  
Open Pollination ◽  
Resistance Level ◽  
Class A ◽  
Class B ◽  
Artificial Inoculations ◽  
Serious Disease ◽  
Blight Disease ◽  
Santa Maria

Fire blight disease caused by pathogenic bacterium Erwinia amylovora, is the serious disease of pear, and there is not a certain chemical management against this disease except antibiotic-type compounds such as streptomycin. It is very important to improve new fire blight resistant cultivars in case of integrated disease management. With this purpose, different crosses have been made between Pyrus communis varieties that have good fruit characteristics and resistant cultigens. Besides, self and open pollination treatments have been carried out in maternal plants. The disease resistance level of the hybrids obtained from these combinations was determined by artificial inoculations by Erwinia amylovora in greenhouse conditions. A total of 3284 hybrids were inoculated, and 2631 of them survived and were distributed to different susceptibility classes. 19.88% of the inoculated hybrids was killed by Erwinia amylovora. Total distribution of the hybrids to susceptibility classes was as 6.18% in class “A- slightly susceptible”, 3.11% in class “B- less susceptible”, 8.89% in class “C- mid-susceptible”, 20.28% in class “D- susceptible”, and 61.54% in class “E- very susceptible”. Majority of class “A- slightly susceptible” hybrids were obtained from ‘Magness’ x ‘Ankara’ combination. ‘Kieffer’ x ‘Santa Maria’, ‘Kieffer’ open pollination, ‘Magness’ x ‘Akça’, ‘Magness’ x ‘Kieffer’, ‘Magness’ x ‘Santa Maria’, ‘Mustafa Bey’ x ‘Moonglow’ treatments displayed good results with respect to “A- slightly susceptible” character. It is very important to evaluate these hybrid pear populations through different fruit and tree characteristics in the future.

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