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Lynda M. Ciuffetti - One of the best experts on this subject based on the ideXlab platform.
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necrotrophic effector epistasis in the Pyrenophora tritici repentis wheat interaction
PLOS ONE, 2015Co-Authors: Viola A. Manning, Lynda M. CiuffettiAbstract:Pyrenophora Tritici-Repentis, the causal agent of tan spot disease of wheat, mediates disease by the production of host-selective toxins (HST). The known toxins are recognized in an ‘inverse’ gene-for-gene manner, where each is perceived by the product of a unique locus in the host and recognition leads to disease susceptibility. Given the importance of HSTs in disease development, we would predict that the loss of any of these major pathogenicity factors would result in reduced virulence and disease development. However, after either deletion of the gene encoding the HST ToxA or, reciprocally, heterologous expression of ToxA in a race that does not normally produce the toxin followed by inoculation of ToxA-sensitive and insensitive wheat cultivars, we demonstrate that ToxA symptom development can be epistatic to other HST-induced symptoms. ToxA epistasis on certain ToxA-sensitive wheat cultivars leads to genotype-specific increases in total leaf area affected by disease. These data indicate a complex interplay between host responses to HSTs in some genotypes and underscore the challenge of identifying additional HSTs whose activity may be masked by other toxins. Also, through mycelial staining, we acquire preliminary evidence that ToxA may provide additional benefits to fungal growth in planta in the absence of its cognate recognition partner in the host.
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solution nmr structures of Pyrenophora tritici repentis toxb and its inactive homolog reveal potential determinants of toxin activity
Journal of Biological Chemistry, 2014Co-Authors: Afua Nyarko, Iovanna Pandelova, Viola A. Manning, Lynda M. Ciuffetti, Melania Figueroa, Kiran Kumar Singarapu, Thomas J Wolpert, Elisar BarbarAbstract:Pyrenophora Tritici-Repentis Ptr ToxB (ToxB) is a proteinaceous host-selective toxin produced by Pyrenophora Tritici-Repentis (P. Tritici-Repentis), a plant pathogenic fungus that causes the disease tan spot of wheat. One feature that distinguishes ToxB from other host-selective toxins is that it has naturally occurring homologs in non-pathogenic P. Tritici-Repentis isolates that lack toxic activity. There are no high-resolution structures for any of the ToxB homologs, or for any protein with >30% sequence identity, and therefore what underlies activity remains an open question. Here, we present the NMR structures of ToxB and its inactive homolog Ptr toxb. Both proteins adopt a β-sandwich fold comprising three strands in each half that are bridged together by two disulfide bonds. The inactive toxb, however, shows higher flexibility localized to the sequence-divergent β-sandwich half. The absence of toxic activity is attributed to a more open structure in the vicinity of one disulfide bond, higher flexibility, and residue differences in an exposed loop that likely impacts interaction with putative targets. We propose that activity is regulated by perturbations in a putative active site loop and changes in dynamics distant from the site of activity. Interestingly, the new structures identify AvrPiz-t, a secreted avirulence protein produced by the rice blast fungus, as a structural homolog to ToxB. This homology suggests that fungal proteins involved in either disease susceptibility such as ToxB or resistance such as AvrPiz-t may have a common evolutionary origin.
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Pyrenophora tritici repentis a plant pathogenic fungus with global impact
Springer-Verlag Berlin Heidelberg, 2014Co-Authors: Lynda M. Ciuffetti, Iovanna Pandelova, Viola A. Manning, Stephen E Strelkov, Thomas J Wolpert, Justin D Faris, Timothy L Friesen, Genevieve Weber, Stephen B Goodwin, Melania FigueroaAbstract:Pyrenophora Tritici-Repentis (Ptr), causal agent of tan spot of wheat, is a necrotrophic fungus that presents an increasing threat to wheat production due to its rapid, global expansion. Despite its homothallic nature, Ptr populations have high genetic diversity, which positively impacts host range and virulence. Pathogenicity by Ptr is attributable to the production of host-selective toxins (HSTs) and follows an inverse gene-for-gene mechanism, in which HSTs are recognized by unique single dominant genes that confer both toxin-sensitivity and disease susceptibility. Studies addressing the mechanism of action of Ptr HSTs have unveiled both commonalities and complexities of the host response to these toxins. Resistance-like host responses triggered by the HSTs support the emerging hypothesis that necrotrophic pathogens exploit the host defense response as a mechanism to induce host cell death and ensure colonization. Recent advances in sequencing technology have facilitated the comparison of the genetic makeup of pathogenic and nonpathogenic isolates of Ptr. Such comparisons are providing insights into the genetic diversity of the pathogen and the mechanisms that dictate the increase in virulence and incidence of this important pathogen. Comparative genome analysis has also provided evidence that transposable elements (TEs) play a crucial role in genome re-arrangement and expansion, which contributes to the genomic flexibility to create and diversify effectors.
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Host-selective toxins of Pyrenophora Tritici-Repentis induce common responses associated with host susceptibility.
PLOS ONE, 2012Co-Authors: Iovanna Pandelova, Larry J. Wilhelm, Viola A. Manning, Aakash N. Mankaney, Melania Figueroa, Todd C. Mockler, Lynda M. CiuffettiAbstract:Pyrenophora Tritici-Repentis (Ptr), a necrotrophic fungus and the causal agent of tan spot of wheat, produces one or a combination of host-selective toxins (HSTs) necessary for disease development. The two most studied toxins produced by Ptr, Ptr ToxA (ToxA) and Ptr ToxB (ToxB), are proteins that cause necrotic or chlorotic symptoms respectively. Investigation of host responses induced by HSTs provides better insight into the nature of the host susceptibility. Microarray analysis of ToxA has provided evidence that it can elicit responses similar to those associated with defense. In order to evaluate whether there are consistent host responses associated with susceptibility, a similar analysis of ToxB-induced changes in the same sensitive cultivar was conducted. Comparative analysis of ToxA- and ToxB-induced transcriptional changes showed that similar groups of genes encoding WRKY transcription factors, RLKs, PRs, components of the phenylpropanoid and jasmonic acid pathways are activated. ROS accumulation and photosystem dysfunction proved to be common mechanism-of-action for these toxins. Despite similarities in defense responses, transcriptional and biochemical responses as well as symptom development occur more rapidly for ToxA compared to ToxB, which could be explained by differences in perception as well as by differences in activation of a specific process, for example, ethylene biosynthesis in ToxA treatment. Results of this study suggest that perception of HSTs will result in activation of defense responses as part of a susceptible interaction and further supports the hypothesis that necrotrophic fungi exploit defense responses in order to induce cell death.
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host selective toxins ptr toxa and ptr toxb as necrotrophic effectors in the Pyrenophora tritici repentis wheat interaction
New Phytologist, 2010Co-Authors: Lynda M. Ciuffetti, Iovanna Pandelova, Viola A. Manning, Melania Figueroa Betts, Patrick J MartinezAbstract:Host-selective toxins (HSTs) are effectors produced by some necrotrophic pathogenic fungi that typically confer the ability to cause disease. Often, diseases caused by pathogens that produce HSTs follow an inverse gene-for-gene model where toxin production is required for the ability to cause disease and a single locus in the host is responsible for toxin sensitivity and disease susceptibility. Pyrenophora Tritici-Repentis represents an ideal pathogen for studying the biological significance of such inverse gene-for-gene interactions, because it displays a complex race structure based on its production of multiple HSTs. Ptr ToxA and Ptr ToxB are two proteinaceous HSTs produced by P. Tritici-Repentis that are structurally unrelated and appear to evoke different host responses, yet each toxin confers the ability to cause disease. This review will summarize the current knowledge of how these two dissimilar HSTs display distinct modes of action, yet each confers pathogenicity to P. Tritici-Repentis.
Caroline S. Moffat - One of the best experts on this subject based on the ideXlab platform.
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The first genome assembly of fungal pathogen Pyrenophora Tritici-Repentis race 1 isolate using Oxford Nanopore MinION sequencing
'Springer Science and Business Media LLC', 2021Co-Authors: Paula Moolhuijzen, Pao Theen See, Caroline S. MoffatAbstract:Abstract Objectives The assembly of fungal genomes using short-reads is challenged by long repetitive and low GC regions. However, long-read sequencing technologies, such as PacBio and Oxford Nanopore, are able to overcome many problematic regions, thereby providing an opportunity to improve fragmented genome assemblies derived from short reads only. Here, a necrotrophic fungal pathogen Pyrenophora Tritici-Repentis (Ptr) isolate 134 (Ptr134), which causes tan spot disease on wheat, was sequenced on a MinION using Oxford Nanopore Technologies (ONT), to improve on a previous Illumina short-read genome assembly and provide a more complete genome resource for pan-genomic analyses of Ptr. Results The genome of Ptr134 sequenced on a MinION using ONT was assembled into 28 contiguous sequences with a total length of 40.79 Mb and GC content of 50.81%. The long-read assembly provided 6.79 Mb of new sequence and 2846 extra annotated protein coding genes as compared to the previous short-read assembly. This improved genome sequence represents near complete chromosomes, an important resource for large scale and pan genomic comparative analyses
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Genetic analysis of wheat sensitivity to the ToxB fungal effector from Pyrenophora Tritici-Repentis, the causal agent of tan spot
Theoretical and Applied Genetics, 2020Co-Authors: Beatrice Corsi, Richard P. Oliver, Pao Theen See, Lawrence Percival-alwyn, Rowena C. Downie, Luca Venturini, Elyce M. Iagallo, Camila Campos Mantello, Charlie Mccormick-barnes, Caroline S. MoffatAbstract:Key message Genetic mapping of sensitivity to the Pyrenophora Tritici-Repentis effector ToxB allowed development of a diagnostic genetic marker, and investigation of wheat pedigrees allowed transmission of sensitive alleles to be tracked. Abstract Tan spot, caused by the necrotrophic fungal pathogen Pyrenophora Tritici-Repentis , is a major disease of wheat ( Triticum aestivum ). Secretion of the P. Tritici-Repentis effector ToxB is thought to play a part in mediating infection, causing chlorosis of plant tissue. Here, genetic analysis using an association mapping panel ( n = 480) and a multiparent advanced generation intercross (MAGIC) population ( n founders = 8, n progeny = 643) genotyped with a 90,000 feature single nucleotide polymorphism (SNP) array found ToxB sensitivity to be highly heritable ( h ^2 ≥ 0.9), controlled predominantly by the Tsc2 locus on chromosome 2B. Genetic mapping of Tsc2 delineated a 1921-kb interval containing 104 genes in the reference genome of ToxB-insensitive variety ‘Chinese Spring’. This allowed development of a co-dominant genetic marker for Tsc2 allelic state, diagnostic for ToxB sensitivity in the association mapping panel. Phenotypic and genotypic analysis in a panel of wheat varieties post-dated the association mapping panel further supported the diagnostic nature of the marker. Combining ToxB phenotype and genotypic data with wheat pedigree datasets allowed historic sources of ToxB sensitivity to be tracked, finding the variety ‘Maris Dove’ to likely be the historic source of sensitive Tsc2 alleles in the wheat germplasm surveyed. Exploration of the Tsc2 region gene space in the ToxB-sensitive line ‘Synthetic W7984’ identified candidate genes for future investigation. Additionally, a minor ToxB sensitivity QTL was identified on chromosome 2A. The resources presented here will be of immediate use for marker-assisted selection for ToxB insensitivity and the development of germplasm with additional genetic recombination within the Tsc2 region.
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genetic analysis of wheat sensitivity to the toxb fungal effector from Pyrenophora tritici repentis the causal agent of tan spot
Theoretical and Applied Genetics, 2020Co-Authors: Beatrice Corsi, Richard P. Oliver, Pao Theen See, Rowena C. Downie, Luca Venturini, Elyce M. Iagallo, Lawrence Percivalalwyn, Camila Campos Mantello, Charlie Mccormickbarnes, Caroline S. MoffatAbstract:Genetic mapping of sensitivity to the Pyrenophora Tritici-Repentis effector ToxB allowed development of a diagnostic genetic marker, and investigation of wheat pedigrees allowed transmission of sensitive alleles to be tracked. Tan spot, caused by the necrotrophic fungal pathogen Pyrenophora Tritici-Repentis, is a major disease of wheat (Triticum aestivum). Secretion of the P. Tritici-Repentis effector ToxB is thought to play a part in mediating infection, causing chlorosis of plant tissue. Here, genetic analysis using an association mapping panel (n = 480) and a multiparent advanced generation intercross (MAGIC) population (n founders = 8, n progeny = 643) genotyped with a 90,000 feature single nucleotide polymorphism (SNP) array found ToxB sensitivity to be highly heritable (h2 ≥ 0.9), controlled predominantly by the Tsc2 locus on chromosome 2B. Genetic mapping of Tsc2 delineated a 1921-kb interval containing 104 genes in the reference genome of ToxB-insensitive variety ‘Chinese Spring’. This allowed development of a co-dominant genetic marker for Tsc2 allelic state, diagnostic for ToxB sensitivity in the association mapping panel. Phenotypic and genotypic analysis in a panel of wheat varieties post-dated the association mapping panel further supported the diagnostic nature of the marker. Combining ToxB phenotype and genotypic data with wheat pedigree datasets allowed historic sources of ToxB sensitivity to be tracked, finding the variety ‘Maris Dove’ to likely be the historic source of sensitive Tsc2 alleles in the wheat germplasm surveyed. Exploration of the Tsc2 region gene space in the ToxB-sensitive line ‘Synthetic W7984’ identified candidate genes for future investigation. Additionally, a minor ToxB sensitivity QTL was identified on chromosome 2A. The resources presented here will be of immediate use for marker-assisted selection for ToxB insensitivity and the development of germplasm with additional genetic recombination within the Tsc2 region.
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the identification and deletion of the polyketide synthase nonribosomal peptide synthase gene responsible for the production of the phytotoxic triticone a b in the wheat fungal pathogen Pyrenophora tritici repentis
Environmental Microbiology, 2019Co-Authors: Catherine Rawlinson, Caroline S. Moffat, Pao Theen See, P Moolhuijzen, Yitheng Chooi, Richard P. OliverAbstract:The economically important necrotrophic fungal pathogen, Pyrenophora Tritici-Repentis (Ptr), causes tan spot of wheat, a disease typified by foliar necrosis and chlorosis. The culture filtrate of an Australian Ptr isolate, M4, possesses phytotoxic activity and plant bioassay guided discovery led to the purification of necrosis inducing toxins called triticone A and B. High-resolution LC-MS/MS analysis of the culture filtrate identified an additional 37 triticone-like compounds. The biosynthetic gene cluster responsible for triticone production (the Ttc cluster) was identified and deletion of TtcA, a hybrid polyketide synthase (PKS)-nonribosomal peptide synthase (NRPS), abolished production of all triticones. The pathogenicity of mutant (ttcA) strains was not visibly affected in our assays. We hypothesize that triticones possess general antimicrobial activity important for competition in multi-microbial environments.
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heterologous expression of the Pyrenophora tritici repentis effector proteins toxa and toxb and the prevalence of effector sensitivity in australian cereal crops
Frontiers in Microbiology, 2019Co-Authors: Pao Theen See, Richard P. Oliver, Elyce M. Iagallo, Caroline S. MoffatAbstract:Here, we evaluate the expression of the proteinaceous effectors ToxA and ToxB, produced by the necrotrophic fungal pathogen Pyrenophora Tritici-Repentis, which confer tan spot disease susceptibility on wheat. These necrotrophic effectors were expressed in two heterologous systems: Escherichia coli and Pichia pastoris. The E. coli SHuffle system was demonstrated to be superior to P. pastoris in generating high-levels of recombinant proteins that were soluble and stable. In addition, protein extracts from P. pastoris induced non-specific chlorosis on wheat, postulated to be caused by co-purified glucanases secreted by the host. Up to 79.6 μg/ml of ToxB was obtained using the SHuffle system in the absence of the native signal peptide, whilst the ToxA yield was considerably lower at 3.2 μg/ml. Results indicated that a histidine tag at the ToxA C-terminus interfered with effector functionality. Heterologously expressed ToxA and ToxB were tested on a panel of Australian cereals, including 122 varieties of bread wheat, 16 durum, 20 triticale and 5 barley varieties, as well as common plant model species including tobacco and Arabidopsis thaliana. A varying degree of effector sensitivities was observed, with a higher ToxB sensitivity and prevalence in the durum and triticale varieties. ToxB-induced chlorosis was also detected on barley. The heterologous expression of effectors that are easily scalable, will facilitate effector-assisted selection of varieties in wheat breeding programs as well as the investigation of P. Tritici-Repentis effectors in host and non-host interactions.
Richard P. Oliver - One of the best experts on this subject based on the ideXlab platform.
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Genetic analysis of wheat sensitivity to the ToxB fungal effector from Pyrenophora Tritici-Repentis, the causal agent of tan spot
Theoretical and Applied Genetics, 2020Co-Authors: Beatrice Corsi, Richard P. Oliver, Pao Theen See, Lawrence Percival-alwyn, Rowena C. Downie, Luca Venturini, Elyce M. Iagallo, Camila Campos Mantello, Charlie Mccormick-barnes, Caroline S. MoffatAbstract:Key message Genetic mapping of sensitivity to the Pyrenophora Tritici-Repentis effector ToxB allowed development of a diagnostic genetic marker, and investigation of wheat pedigrees allowed transmission of sensitive alleles to be tracked. Abstract Tan spot, caused by the necrotrophic fungal pathogen Pyrenophora Tritici-Repentis , is a major disease of wheat ( Triticum aestivum ). Secretion of the P. Tritici-Repentis effector ToxB is thought to play a part in mediating infection, causing chlorosis of plant tissue. Here, genetic analysis using an association mapping panel ( n = 480) and a multiparent advanced generation intercross (MAGIC) population ( n founders = 8, n progeny = 643) genotyped with a 90,000 feature single nucleotide polymorphism (SNP) array found ToxB sensitivity to be highly heritable ( h ^2 ≥ 0.9), controlled predominantly by the Tsc2 locus on chromosome 2B. Genetic mapping of Tsc2 delineated a 1921-kb interval containing 104 genes in the reference genome of ToxB-insensitive variety ‘Chinese Spring’. This allowed development of a co-dominant genetic marker for Tsc2 allelic state, diagnostic for ToxB sensitivity in the association mapping panel. Phenotypic and genotypic analysis in a panel of wheat varieties post-dated the association mapping panel further supported the diagnostic nature of the marker. Combining ToxB phenotype and genotypic data with wheat pedigree datasets allowed historic sources of ToxB sensitivity to be tracked, finding the variety ‘Maris Dove’ to likely be the historic source of sensitive Tsc2 alleles in the wheat germplasm surveyed. Exploration of the Tsc2 region gene space in the ToxB-sensitive line ‘Synthetic W7984’ identified candidate genes for future investigation. Additionally, a minor ToxB sensitivity QTL was identified on chromosome 2A. The resources presented here will be of immediate use for marker-assisted selection for ToxB insensitivity and the development of germplasm with additional genetic recombination within the Tsc2 region.
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genetic analysis of wheat sensitivity to the toxb fungal effector from Pyrenophora tritici repentis the causal agent of tan spot
Theoretical and Applied Genetics, 2020Co-Authors: Beatrice Corsi, Richard P. Oliver, Pao Theen See, Rowena C. Downie, Luca Venturini, Elyce M. Iagallo, Lawrence Percivalalwyn, Camila Campos Mantello, Charlie Mccormickbarnes, Caroline S. MoffatAbstract:Genetic mapping of sensitivity to the Pyrenophora Tritici-Repentis effector ToxB allowed development of a diagnostic genetic marker, and investigation of wheat pedigrees allowed transmission of sensitive alleles to be tracked. Tan spot, caused by the necrotrophic fungal pathogen Pyrenophora Tritici-Repentis, is a major disease of wheat (Triticum aestivum). Secretion of the P. Tritici-Repentis effector ToxB is thought to play a part in mediating infection, causing chlorosis of plant tissue. Here, genetic analysis using an association mapping panel (n = 480) and a multiparent advanced generation intercross (MAGIC) population (n founders = 8, n progeny = 643) genotyped with a 90,000 feature single nucleotide polymorphism (SNP) array found ToxB sensitivity to be highly heritable (h2 ≥ 0.9), controlled predominantly by the Tsc2 locus on chromosome 2B. Genetic mapping of Tsc2 delineated a 1921-kb interval containing 104 genes in the reference genome of ToxB-insensitive variety ‘Chinese Spring’. This allowed development of a co-dominant genetic marker for Tsc2 allelic state, diagnostic for ToxB sensitivity in the association mapping panel. Phenotypic and genotypic analysis in a panel of wheat varieties post-dated the association mapping panel further supported the diagnostic nature of the marker. Combining ToxB phenotype and genotypic data with wheat pedigree datasets allowed historic sources of ToxB sensitivity to be tracked, finding the variety ‘Maris Dove’ to likely be the historic source of sensitive Tsc2 alleles in the wheat germplasm surveyed. Exploration of the Tsc2 region gene space in the ToxB-sensitive line ‘Synthetic W7984’ identified candidate genes for future investigation. Additionally, a minor ToxB sensitivity QTL was identified on chromosome 2A. The resources presented here will be of immediate use for marker-assisted selection for ToxB insensitivity and the development of germplasm with additional genetic recombination within the Tsc2 region.
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the identification and deletion of the polyketide synthase nonribosomal peptide synthase gene responsible for the production of the phytotoxic triticone a b in the wheat fungal pathogen Pyrenophora tritici repentis
Environmental Microbiology, 2019Co-Authors: Catherine Rawlinson, Caroline S. Moffat, Pao Theen See, P Moolhuijzen, Yitheng Chooi, Richard P. OliverAbstract:The economically important necrotrophic fungal pathogen, Pyrenophora Tritici-Repentis (Ptr), causes tan spot of wheat, a disease typified by foliar necrosis and chlorosis. The culture filtrate of an Australian Ptr isolate, M4, possesses phytotoxic activity and plant bioassay guided discovery led to the purification of necrosis inducing toxins called triticone A and B. High-resolution LC-MS/MS analysis of the culture filtrate identified an additional 37 triticone-like compounds. The biosynthetic gene cluster responsible for triticone production (the Ttc cluster) was identified and deletion of TtcA, a hybrid polyketide synthase (PKS)-nonribosomal peptide synthase (NRPS), abolished production of all triticones. The pathogenicity of mutant (ttcA) strains was not visibly affected in our assays. We hypothesize that triticones possess general antimicrobial activity important for competition in multi-microbial environments.
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heterologous expression of the Pyrenophora tritici repentis effector proteins toxa and toxb and the prevalence of effector sensitivity in australian cereal crops
Frontiers in Microbiology, 2019Co-Authors: Pao Theen See, Richard P. Oliver, Elyce M. Iagallo, Caroline S. MoffatAbstract:Here, we evaluate the expression of the proteinaceous effectors ToxA and ToxB, produced by the necrotrophic fungal pathogen Pyrenophora Tritici-Repentis, which confer tan spot disease susceptibility on wheat. These necrotrophic effectors were expressed in two heterologous systems: Escherichia coli and Pichia pastoris. The E. coli SHuffle system was demonstrated to be superior to P. pastoris in generating high-levels of recombinant proteins that were soluble and stable. In addition, protein extracts from P. pastoris induced non-specific chlorosis on wheat, postulated to be caused by co-purified glucanases secreted by the host. Up to 79.6 μg/ml of ToxB was obtained using the SHuffle system in the absence of the native signal peptide, whilst the ToxA yield was considerably lower at 3.2 μg/ml. Results indicated that a histidine tag at the ToxA C-terminus interfered with effector functionality. Heterologously expressed ToxA and ToxB were tested on a panel of Australian cereals, including 122 varieties of bread wheat, 16 durum, 20 triticale and 5 barley varieties, as well as common plant model species including tobacco and Arabidopsis thaliana. A varying degree of effector sensitivities was observed, with a higher ToxB sensitivity and prevalence in the durum and triticale varieties. ToxB-induced chlorosis was also detected on barley. The heterologous expression of effectors that are easily scalable, will facilitate effector-assisted selection of varieties in wheat breeding programs as well as the investigation of P. Tritici-Repentis effectors in host and non-host interactions.
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Table_2_Heterologous Expression of the Pyrenophora Tritici-Repentis Effector Proteins ToxA and ToxB, and the Prevalence of Effector Sensitivity in Australian Cereal Crops.docx
2019Co-Authors: Pao Theen See, Richard P. Oliver, Elyce M. Iagallo, Caroline S. MoffatAbstract:Here, we evaluate the expression of the proteinaceous effectors ToxA and ToxB, produced by the necrotrophic fungal pathogen Pyrenophora Tritici-Repentis, which confer tan spot disease susceptibility on wheat. These necrotrophic effectors were expressed in two heterologous systems: Escherichia coli and Pichia pastoris. The E. coli SHuffle system was demonstrated to be superior to P. pastoris in generating high-levels of recombinant proteins that were soluble and stable. In addition, protein extracts from P. pastoris induced non-specific chlorosis on wheat, postulated to be caused by co-purified glucanases secreted by the host. Up to 79.6 μg/ml of ToxB was obtained using the SHuffle system in the absence of the native signal peptide, whilst the ToxA yield was considerably lower at 3.2 μg/ml. Results indicated that a histidine tag at the ToxA C-terminus interfered with effector functionality. Heterologously expressed ToxA and ToxB were tested on a panel of Australian cereals, including 122 varieties of bread wheat, 16 durum, 20 triticale and 5 barley varieties, as well as common plant model species including tobacco and Arabidopsis thaliana. A varying degree of effector sensitivities was observed, with a higher ToxB sensitivity and prevalence in the durum and triticale varieties. ToxB-induced chlorosis was also detected on barley. The heterologous expression of effectors that are easily scalable, will facilitate effector-assisted selection of varieties in wheat breeding programs as well as the investigation of P. Tritici-Repentis effectors in host and non-host interactions.
Pao Theen See - One of the best experts on this subject based on the ideXlab platform.
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The first genome assembly of fungal pathogen Pyrenophora Tritici-Repentis race 1 isolate using Oxford Nanopore MinION sequencing
'Springer Science and Business Media LLC', 2021Co-Authors: Paula Moolhuijzen, Pao Theen See, Caroline S. MoffatAbstract:Abstract Objectives The assembly of fungal genomes using short-reads is challenged by long repetitive and low GC regions. However, long-read sequencing technologies, such as PacBio and Oxford Nanopore, are able to overcome many problematic regions, thereby providing an opportunity to improve fragmented genome assemblies derived from short reads only. Here, a necrotrophic fungal pathogen Pyrenophora Tritici-Repentis (Ptr) isolate 134 (Ptr134), which causes tan spot disease on wheat, was sequenced on a MinION using Oxford Nanopore Technologies (ONT), to improve on a previous Illumina short-read genome assembly and provide a more complete genome resource for pan-genomic analyses of Ptr. Results The genome of Ptr134 sequenced on a MinION using ONT was assembled into 28 contiguous sequences with a total length of 40.79 Mb and GC content of 50.81%. The long-read assembly provided 6.79 Mb of new sequence and 2846 extra annotated protein coding genes as compared to the previous short-read assembly. This improved genome sequence represents near complete chromosomes, an important resource for large scale and pan genomic comparative analyses
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Genetic analysis of wheat sensitivity to the ToxB fungal effector from Pyrenophora Tritici-Repentis, the causal agent of tan spot
Theoretical and Applied Genetics, 2020Co-Authors: Beatrice Corsi, Richard P. Oliver, Pao Theen See, Lawrence Percival-alwyn, Rowena C. Downie, Luca Venturini, Elyce M. Iagallo, Camila Campos Mantello, Charlie Mccormick-barnes, Caroline S. MoffatAbstract:Key message Genetic mapping of sensitivity to the Pyrenophora Tritici-Repentis effector ToxB allowed development of a diagnostic genetic marker, and investigation of wheat pedigrees allowed transmission of sensitive alleles to be tracked. Abstract Tan spot, caused by the necrotrophic fungal pathogen Pyrenophora Tritici-Repentis , is a major disease of wheat ( Triticum aestivum ). Secretion of the P. Tritici-Repentis effector ToxB is thought to play a part in mediating infection, causing chlorosis of plant tissue. Here, genetic analysis using an association mapping panel ( n = 480) and a multiparent advanced generation intercross (MAGIC) population ( n founders = 8, n progeny = 643) genotyped with a 90,000 feature single nucleotide polymorphism (SNP) array found ToxB sensitivity to be highly heritable ( h ^2 ≥ 0.9), controlled predominantly by the Tsc2 locus on chromosome 2B. Genetic mapping of Tsc2 delineated a 1921-kb interval containing 104 genes in the reference genome of ToxB-insensitive variety ‘Chinese Spring’. This allowed development of a co-dominant genetic marker for Tsc2 allelic state, diagnostic for ToxB sensitivity in the association mapping panel. Phenotypic and genotypic analysis in a panel of wheat varieties post-dated the association mapping panel further supported the diagnostic nature of the marker. Combining ToxB phenotype and genotypic data with wheat pedigree datasets allowed historic sources of ToxB sensitivity to be tracked, finding the variety ‘Maris Dove’ to likely be the historic source of sensitive Tsc2 alleles in the wheat germplasm surveyed. Exploration of the Tsc2 region gene space in the ToxB-sensitive line ‘Synthetic W7984’ identified candidate genes for future investigation. Additionally, a minor ToxB sensitivity QTL was identified on chromosome 2A. The resources presented here will be of immediate use for marker-assisted selection for ToxB insensitivity and the development of germplasm with additional genetic recombination within the Tsc2 region.
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genetic analysis of wheat sensitivity to the toxb fungal effector from Pyrenophora tritici repentis the causal agent of tan spot
Theoretical and Applied Genetics, 2020Co-Authors: Beatrice Corsi, Richard P. Oliver, Pao Theen See, Rowena C. Downie, Luca Venturini, Elyce M. Iagallo, Lawrence Percivalalwyn, Camila Campos Mantello, Charlie Mccormickbarnes, Caroline S. MoffatAbstract:Genetic mapping of sensitivity to the Pyrenophora Tritici-Repentis effector ToxB allowed development of a diagnostic genetic marker, and investigation of wheat pedigrees allowed transmission of sensitive alleles to be tracked. Tan spot, caused by the necrotrophic fungal pathogen Pyrenophora Tritici-Repentis, is a major disease of wheat (Triticum aestivum). Secretion of the P. Tritici-Repentis effector ToxB is thought to play a part in mediating infection, causing chlorosis of plant tissue. Here, genetic analysis using an association mapping panel (n = 480) and a multiparent advanced generation intercross (MAGIC) population (n founders = 8, n progeny = 643) genotyped with a 90,000 feature single nucleotide polymorphism (SNP) array found ToxB sensitivity to be highly heritable (h2 ≥ 0.9), controlled predominantly by the Tsc2 locus on chromosome 2B. Genetic mapping of Tsc2 delineated a 1921-kb interval containing 104 genes in the reference genome of ToxB-insensitive variety ‘Chinese Spring’. This allowed development of a co-dominant genetic marker for Tsc2 allelic state, diagnostic for ToxB sensitivity in the association mapping panel. Phenotypic and genotypic analysis in a panel of wheat varieties post-dated the association mapping panel further supported the diagnostic nature of the marker. Combining ToxB phenotype and genotypic data with wheat pedigree datasets allowed historic sources of ToxB sensitivity to be tracked, finding the variety ‘Maris Dove’ to likely be the historic source of sensitive Tsc2 alleles in the wheat germplasm surveyed. Exploration of the Tsc2 region gene space in the ToxB-sensitive line ‘Synthetic W7984’ identified candidate genes for future investigation. Additionally, a minor ToxB sensitivity QTL was identified on chromosome 2A. The resources presented here will be of immediate use for marker-assisted selection for ToxB insensitivity and the development of germplasm with additional genetic recombination within the Tsc2 region.
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the identification and deletion of the polyketide synthase nonribosomal peptide synthase gene responsible for the production of the phytotoxic triticone a b in the wheat fungal pathogen Pyrenophora tritici repentis
Environmental Microbiology, 2019Co-Authors: Catherine Rawlinson, Caroline S. Moffat, Pao Theen See, P Moolhuijzen, Yitheng Chooi, Richard P. OliverAbstract:The economically important necrotrophic fungal pathogen, Pyrenophora Tritici-Repentis (Ptr), causes tan spot of wheat, a disease typified by foliar necrosis and chlorosis. The culture filtrate of an Australian Ptr isolate, M4, possesses phytotoxic activity and plant bioassay guided discovery led to the purification of necrosis inducing toxins called triticone A and B. High-resolution LC-MS/MS analysis of the culture filtrate identified an additional 37 triticone-like compounds. The biosynthetic gene cluster responsible for triticone production (the Ttc cluster) was identified and deletion of TtcA, a hybrid polyketide synthase (PKS)-nonribosomal peptide synthase (NRPS), abolished production of all triticones. The pathogenicity of mutant (ttcA) strains was not visibly affected in our assays. We hypothesize that triticones possess general antimicrobial activity important for competition in multi-microbial environments.
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heterologous expression of the Pyrenophora tritici repentis effector proteins toxa and toxb and the prevalence of effector sensitivity in australian cereal crops
Frontiers in Microbiology, 2019Co-Authors: Pao Theen See, Richard P. Oliver, Elyce M. Iagallo, Caroline S. MoffatAbstract:Here, we evaluate the expression of the proteinaceous effectors ToxA and ToxB, produced by the necrotrophic fungal pathogen Pyrenophora Tritici-Repentis, which confer tan spot disease susceptibility on wheat. These necrotrophic effectors were expressed in two heterologous systems: Escherichia coli and Pichia pastoris. The E. coli SHuffle system was demonstrated to be superior to P. pastoris in generating high-levels of recombinant proteins that were soluble and stable. In addition, protein extracts from P. pastoris induced non-specific chlorosis on wheat, postulated to be caused by co-purified glucanases secreted by the host. Up to 79.6 μg/ml of ToxB was obtained using the SHuffle system in the absence of the native signal peptide, whilst the ToxA yield was considerably lower at 3.2 μg/ml. Results indicated that a histidine tag at the ToxA C-terminus interfered with effector functionality. Heterologously expressed ToxA and ToxB were tested on a panel of Australian cereals, including 122 varieties of bread wheat, 16 durum, 20 triticale and 5 barley varieties, as well as common plant model species including tobacco and Arabidopsis thaliana. A varying degree of effector sensitivities was observed, with a higher ToxB sensitivity and prevalence in the durum and triticale varieties. ToxB-induced chlorosis was also detected on barley. The heterologous expression of effectors that are easily scalable, will facilitate effector-assisted selection of varieties in wheat breeding programs as well as the investigation of P. Tritici-Repentis effectors in host and non-host interactions.
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characterization of Pyrenophora tritici repentis in tunisia and comparison with a global pathogen population
Plant Disease, 2021Co-Authors: Marwa Laribi, Stephen E Strelkov, Amor Yahyaoui, Alireza Akhavan, Sarrah Ben Mbarek, Khaled SassiAbstract:Pyrenophora Tritici-Repentis (Ptr) causes tan spot, an important foliar disease of wheat. A collection of Ptr isolates from Tunisia, located in one of the main secondary centers of diversification of durum wheat, was tested for phenotypic race classification based on virulence on a host differential set, and for the presence of the necrotrophic effector (NE) genes ToxA, ToxB , and toxb by PCR analysis. While races 2, 4, 5, 6, 7, and 8 were identified according to their virulence phenotypes, PCR testing indicated the presence of 'atypical' isolates that induced necrosis on the wheat differential 'Glenlea', but lacked the expected ToxA gene, suggesting the involvement of other NEs in the Ptr/wheat interaction. Genetic diversity and the Ptr population structure were explored further by examining 59 Tunisian isolates and 35 isolates from Algeria, Azerbaijan, Canada, Iran, and Syria using 24 simple sequence repeat markers. Average genetic diversity, overall gene flow and percentage polymorphic loci were estimated as 0.58, 2.09 and 87%, respectively. Analysis of molecular variance showed that 81% of the genetic variance occurred within populations and 19% between populations. Cluster analysis by the unweighted pair group method indicated that ToxB- isolates grouped together and were distantly related to ToxB+ isolates. Based on Nei's analysis, the global collection clustered into two distinct groups according to their region of origin. The results suggest that both geographic origin and the host-specificity imposed by different NEs can lead to differentiation among Ptr populations.
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race distribution of Pyrenophora tritici repentis in relation to ploidy level and susceptibility of durum and winter bread wheat
Canadian Journal of Plant Pathology-revue Canadienne De Phytopathologie, 2021Co-Authors: Stephen E Strelkov, Bohan Wei, Therese Despins, M R Fernandez, Yuefeng Ruan, R J Graf, Reem AboukhaddourAbstract:Tan spot is a destructive disease of wheat caused by the fungus Pyrenophora Tritici-Repentis (Ptr), with most fungal isolates in Canada known to produce the necrotrophic effector (NE) ToxA. In this...
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Simple sequence repeat marker analysis reveals grouping of Pyrenophora Tritici-Repentis isolates based on geographic origin
2019Co-Authors: Hassan Momeni, Reem Aboukhaddour, Alireza Akhavan, Mohammad Javan-nikkhah, Mohammad Razavi, Mohammad Reza Naghavi, Stephen E StrelkovAbstract:The population structure and genetic diversity of Pyrenophora Tritici-Repentis from hexaploid wheat were examined using 51 simple sequence repeat (SSR) markers designed to represent each chromosome of the pathogen. A total of 83 isolates representing races 1 and 2 of Ptr were analysed, including 35 isolates from Canada and 48 isolates from Iran. Isolates of the same two races but originating from different regions were compared in order to examine the effect of geographic origin on grouping. Most of the variation (91%) was observed within the examined populations and only 9% between populations. In addition, a moderate amount of gene flow (Nm = 2.8134) was found between populations. The average gene diversity and the percentage of polymorphic loci were estimated to be 0.2764 and 68.63%, respectively. Applying the unweighted pair group method with arithmetic mean procedure and Dice similarity coefficient revealed no obvious clustering of isolates based on race designation. In contrast, the grouping of isolates was consistent with geographic origin to some extent, with most isolates from Iran and Canada clustering separately regardless of race. These results indicate a link between geographic origin and the grouping of Ptr isolates, which could be detected by comparison of the same two races from two different regions. Previous research compared variable races, making it difficult to draw conclusions regarding the effect of geographic origin.
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race characterization of Pyrenophora tritici repentis and sensitivity to propiconazole and pyraclostrobin fungicides
Canadian Journal of Plant Pathology-revue Canadienne De Phytopathologie, 2017Co-Authors: Dustin Maclean, Stephen E Strelkov, Reem Aboukhaddour, Van Anh Tran, Homa Askarian, Kelly T Turkington, Hadley R KutcherAbstract:AbstractTan spot, caused by Pyrenophora Tritici-Repentis (Ptr), is one of the most destructive leaf spot diseases of wheat in Canada. Several races of the fungus are known to occur. Wheat growers have adopted fungicides to manage tan spot; however, intensive spraying may lead to development of reduced sensitivity to fungicides in the pathogen. In this study, 62 Ptr isolates were collected from across Saskatchewan and Alberta and characterized to race on a wheat differential set, with confirmation of race designations by polymerase chain reaction. This same set of isolates, and 27 isolates from an earlier study, were also evaluated for sensitivity to propiconazole and pyraclostrobin fungicides by determining the effective concentration of each needed to inhibit radial growth and conidiospore germination by 50%. Races 1 and 2 were predominant in western Canada, with 57% of isolates classified as race 1 and 40% as race 2. In Alberta, race 1 was most common (76%), while in Saskatchewan, it was race 2 (57%). T...
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Race characterization of Pyrenophora Tritici-Repentis and sensitivity to propiconazole and pyraclostrobin fungicides
2017Co-Authors: Dustin E. Maclean, Stephen E Strelkov, Reem Aboukhaddour, Van Anh Tran, Homa Askarian, Kelly T Turkington, Hadley R KutcherAbstract:Tan spot, caused by Pyrenophora Tritici-Repentis (Ptr), is one of the most destructive leaf spot diseases of wheat in Canada. Several races of the fungus are known to occur. Wheat growers have adopted fungicides to manage tan spot; however, intensive spraying may lead to development of reduced sensitivity to fungicides in the pathogen. In this study, 62 Ptr isolates were collected from across Saskatchewan and Alberta and characterized to race on a wheat differential set, with confirmation of race designations by polymerase chain reaction. This same set of isolates, and 27 isolates from an earlier study, were also evaluated for sensitivity to propiconazole and pyraclostrobin fungicides by determining the effective concentration of each needed to inhibit radial growth and conidiospore germination by 50%. Races 1 and 2 were predominant in western Canada, with 57% of isolates classified as race 1 and 40% as race 2. In Alberta, race 1 was most common (76%), while in Saskatchewan, it was race 2 (57%). Two of 26 isolates were classified as race 3, which was detected only in Saskatchewan in 2013. There was no evidence of reduced sensitivity of either fungicide in the Ptr isolates examined. This study provides a baseline for Ptr sensitivity to propiconazole and pyraclostrobin to which future collections of the pathogen may be compared.
