The Experts below are selected from a list of 606 Experts worldwide ranked by ideXlab platform
John K Scott - One of the best experts on this subject based on the ideXlab platform.
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pathogens on wild radish raphanus raphanistrum brassicaceae in south western australia implications for biological control
Australasian Plant Pathology, 2008Co-Authors: Aaron Maxwell, John K ScottAbstract:Biological control options for wild radish (Raphanus raphanistrum L.) were explored through a pathogen survey in south-western Australia, inoculation studies and a literature review. Twelve fungal species were isolated from diseased wild radish, including an undescribed species of Mycosphaerella and Hyaloperonospora Parasitica, which have not been previously recorded on wild radish in Western Australia. H. Parasitica was the most damaging and widespread pathogen of wild radish. Phylogenetic analysis based on the internal transcribed spacer regions of the rRNA genes showed that the H. Parasitica isolates from wild radish are genetically distinct from the isolates found on Brassica species including canola. This finding opens up the possibility of developing a conservation or augmentative approach to the biological control of wild radish using H. Parasitica. The possibility of using other pathogens in a biocontrol strategy is remote because of likely nontarget effects on canola. Leptosphaeria biglobosa and L. maculans were widespread pathogens of wild radish suggesting this weed may provide an inoculum source for blackleg disease on canola (Brassica napus) by providing a bridge to disease along roadsides and paddocks throughout grain-growing areas.
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Pathogens on wild radish, Raphanus raphanistrum (Brassicaceae), in south-western Australia — implications for biological control
Australasian Plant Pathology, 2008Co-Authors: Aaron Maxwell, John K ScottAbstract:Biological control options for wild radish (Raphanus raphanistrum L.) were explored through a pathogen survey in south-western Australia, inoculation studies and a literature review. Twelve fungal species were isolated from diseased wild radish, including an undescribed species of Mycosphaerella and Hyaloperonospora Parasitica, which have not been previously recorded on wild radish in Western Australia. H. Parasitica was the most damaging and widespread pathogen of wild radish. Phylogenetic analysis based on the internal transcribed spacer regions of the rRNA genes showed that the H. Parasitica isolates from wild radish are genetically distinct from the isolates found on Brassica species including canola. This finding opens up the possibility of developing a conservation or augmentative approach to the biological control of wild radish using H. Parasitica. The possibility of using other pathogens in a biocontrol strategy is remote because of likely nontarget effects on canola. Leptosphaeria biglobosa and L. maculans were widespread pathogens of wild radish suggesting this weed may provide an inoculum source for blackleg disease on canola (Brassica napus) by providing a bridge to disease along roadsides and paddocks throughout grain-growing areas.
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Opportunities for the Control of Brassicaceous Weeds of Cropping Systems Using Mycoherbicides
Advances in Botanical Research, 2005Co-Authors: Aaron Maxwell, John K ScottAbstract:Mycoherbicides offer another option in controlling weeds, especially in light of increasing problems with herbicide resistance. Wild radish is a weed of cropping systems for which pathogens found in Australia include a suite of species with differing host range that could be developed into mycoherbicides useful against weed species from the Brassicaceae. Potentially useful fungal pathogens found in Australia are Alternaria alternata, A. brassicae, A. brassicicola, A. japonica, Fusarium oxysporum, and Hyaloperonospora Parasitica. Mycoherbicide candidates are considered in terms of their host specificity, virulence, epidemiological properties, industrial scale inoculum production, and suitability for liquid or solid formulation. Another critical issue is how to avoid nontarget damage in crops of the Brassicaceae such as canola. Hyaloperonospora Parasitica has potentially the most specific pathovars for the control of wild radish, but is not well suited for mycoherbicide production. Whereas Alternaria japonica is less host specific than H. Parasitica, it is probably the most suited for development as a mycoherbicide. This review identifies opportunities to overcome some of the limitations associated with delivering reliable bioherbicide technology through improved identification of pathogens associated with Brassicaceae, a better understanding of their epidemiology, and possible modifications to improve their mycoherbicide potential.
D. M. Cahill - One of the best experts on this subject based on the ideXlab platform.
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UV-Induced DNA Damage Promotes Resistance to the Biotrophic Pathogen Hyaloperonospora Parasitica in Arabidopsis
PLANT PHYSIOLOGY, 2008Co-Authors: B A Kunz, P. K. Dando, D. M. Grice, P. G. Mohr, P. M. Schenk, D. M. CahillAbstract:Plant innate immunity to pathogenic microorganisms is activated in response to recognition of extracellular or intracellular pathogen molecules by transmembrane receptors or resistance proteins, respectively. The defense signaling pathways share components with those involved in plant responses to UV radiation, which can induce expression of plant genes important for pathogen resistance. Such intriguing links suggest that UV treatment might activate resistance to pathogens in normally susceptible host plants. Here, we demonstrate that pre-inoculative UV (254 nm) irradiation of Arabidopsis (Arabidopsis thaliana) susceptible to infection by the biotrophic oomycete Hyaloperonospora Parasitica, the causative agent of downy mildew, induces dose- and time-dependent resistance to the pathogen detectable up to 7 d after UV exposure. Limiting repair of UV photoproducts by postirradiation incubation in the dark, or mutational inactivation of cyclobutane pyrimidine dimer photolyase, (6-4) photoproduct photolyase, or nucleotide excision repair increased the magnitude of UV-induced pathogen resistance. In the absence of treatment with 254-nm UV, plant nucleotide excision repair mutants also defective for cyclobutane pyrimidine dimer or (6-4) photoproduct photolyase displayed resistance to H. Parasitica, partially attributable to short wavelength UV-B (280-320 nm) radiation emitted by incubator lights. These results indicate UV irradiation can initiate the development of resistance to H. Parasitica in plants normally susceptible to the pathogen and point to a key role for UV-induced DNA damage. They also suggest UV treatment can circumvent the requirement for recognition of H. Parasitica molecules by Arabidopsis proteins to activate an immune response.
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UV induces resistance in Arabidopsis Thaliana to the Oomycete Pathogen Hyaloperonospora Parasitica
2006Co-Authors: D. M. Cahill, B A Kunz, P. Dando, D. Grice, B. Wade, K. MckenzieAbstract:Owing to their sessile nature, plants have evolved mechanisms to minimise the damaging effects of abiotic and biotic stresses. Attack by pathogenic fungi, viruses and bacterium is a major type of biotic stress. To resist infection, plants recognise invading pathogens and induce disease resistance through multiple signal transduction pathways. In addition, appropriate stimulation can cause plants to increase their resistance to future pathogen attack. We have found that exposure to non-lethal doses of UV-C (254 nm) renders a normally susceptible ecotype of Arabidopsis thaliana resistant to the biotrophic Oomycete pathogen Hyaloperonospora Parasitica. The UV treatment induces an incompatible response in a dose-dependent fashion, and is still effective upon pathogen inoculation up to seven days after UV exposure. The degree of resistance diminishes with time but higher doses result in greater levels of resistance, even after seven days. Furthermore, the effect is systemic, occurring in parts of the plant that have not been irradiated. Incubation in the dark post?irradiation and prior to infection reduces the UV dose required to generate a specific level of pathogen resistance without affecting the duration of resistance. These observations, plus the inability of plants to photoreactivate UV photoproducts in the dark, strongly suggest that DNA damage induces the resistance phenotype. Currently, we are assessing the influence of DNA repair defects on UV-induced resistance, following the expression of a number of defence?related genes post-UV-C irradiation, and assessing the effect of UV in plant mutants deficient in specific signalling molecules involved in resistance.
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DNA repair deficiencies increase the resistance of Arabidopsis Thaliana to Hyaloperonospora Parasitica
2006Co-Authors: D. Grice, P. G. Mohr, B A Kunz, P. Dando, B. Wade, K. Mckenzie, D. M. CahillAbstract:We have found that UV-C treatment of Arabidopsis thaliana induces resistance to the biotrophic pathogen Hyaloperonospora Parasitica, and our data suggest UV induced DNA photoproducts are involved (see accompanying abstract by K.G. McKenzie et al.). To address the potential role of DNA damage, we have examined the effect of mutations in nucleotide excision repair (uvr1-1), photoreactivation of cyclobutane pyrimidine dimers (uvr2-1) or flavonoid production (tt5) on the resistance of Arabidopsis to the pathogen with or without pre-inoculation treatment with UV-C. In the mutant backgrounds, UV-C induced pathogen resistance (as measured by decreased conidiophore formation) to the same degree as in the wildtype plants, but much lower UV doses were required (e.g., 100 Jm-2 in the mutant vs. 400 Jm-2 in the wildtype). This is the result expected if damage to DNA rather than a non DNA target is involved. Interestingly, in the absence of UV-C, the tt5 mutation alone resulted in a slight increase in resistance. However, when coupled with uvr1-1, resistance was enhanced to an even greater extent. Remarkably, the tt5 uvr1-1 uvr2-1 triple mutant was completely resistant to the pathogen. Since tt5 mutants are sensitive to reactive oxygen species, which can cause DNA damage susceptible to nucleotide excision repair, our results suggest that in addition to UV photoproducts, an accumulation of endogenous oxidative DNA damage may also trigger resistance to the pathogen. We are currently examining pathogen resistance in other DNA repair deficient mutants, and quantifying UV-C-induced DNA damage in Arabidopsis in order to assess the relationship between damage levels and the extent of resistance.
Byung-kook Hwang - One of the best experts on this subject based on the ideXlab platform.
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The pepper calmodulin gene CaCaM1 is involved in reactive oxygen species and nitric oxide generation required for cell death and the defense response.
Molecular plant-microbe interactions : MPMI, 2009Co-Authors: Hyong Woo Choi, Dong Hyuk Lee, Byung-kook HwangAbstract:Calcium signaling has emerged as an important signal transduction pathway of higher plants in response to biotic and abiotic stresses. Ca2+-bound calmodulin (CaM) plays a critical role in decoding and transducing stress signals by activating specific targets. Here, we isolated and functionally characterized the pathogen-responsive CaM gene, Capsicum annuum calmodulin 1 (CaCaM1), from pepper (C. annuum) plants. The cellular function of CaCaM1 was verified by Agrobacterium spp.-mediated transient expression in pepper and transgenic overexpression in Arabidopsis thaliana. Agrobacterium spp.-mediated transient expression of CaCaM1 activated reactive oxygen species (ROS), nitric oxide (NO) generation, and hypersensitive response (HR)-like cell death in pepper leaves, ultimately leading to local acquired resistance to Xanthomonas campestris pv. vesicatoria. CaCaM1-overexpression (OX) Arabidopsis exhibited enhanced resistance to Pseudomonas syringae and Hyaloperonospora Parasitica, which was accompanied by enhan...
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a role for a menthone reductase in resistance against microbial pathogens in plants
Plant Physiology, 2008Co-Authors: Hyong Woo Choi, Yong Park, Hyun Kyu Song, Byung-kook HwangAbstract:Plants elaborate a vast array of enzymes that synthesize defensive secondary metabolites in response to pathogen attack. Here, we isolated the pathogen-responsive CaMNR1 [menthone: (+)-(3S)-neomenthol reductase] gene, a member of the short-chain dehydrogenase/reductase (SDR) superfamily, from pepper (Capsicum annuum) plants. Gas chromatography-mass spectrometry analysis revealed that purified CaMNR1 and its ortholog AtSDR1 from Arabidopsis (Arabidopsis thaliana) catalyze a menthone reduction with reduced nicotinamide adenine dinucleotide phosphate as a cofactor to produce neomenthol with antimicrobial activity. CaMNR1 and AtSDR1 also possess a significant catalytic activity for neomenthol oxidation. We examined the cellular function of the CaMNR1 gene by virus-induced gene silencing and ectopic overexpression in pepper and Arabidopsis plants, respectively. CaMNR1-silenced pepper plants were significantly more susceptible to Xanthomonas campestris pv vesicatoria and Colletotrichum coccodes infection and expressed lower levels of salicylic acid-responsive CaBPR1 and CaPR10 and jasmonic acid-responsive CaDEF1. CaMNR1-overexpressing Arabidopsis plants exhibited enhanced resistance to the hemibiotrophic pathogen Pseudomonas syringae pv tomato DC3000 and the biotrophic pathogen Hyaloperonospora Parasitica isolate Noco2, accompanied by the induction of AtPR1 and AtPDF1.2. In contrast, mutation in the CaMNR1 ortholog AtSDR1 significantly enhanced susceptibility to both pathogens. Together, these results indicate that the novel menthone reductase gene CaMNR1 and its ortholog AtSDR1 positively regulate plant defenses against a broad spectrum of pathogens.
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Distinct roles of the pepper pathogen-induced membrane protein gene CaPIMP1 in bacterial disease resistance and oomycete disease susceptibility
Planta, 2008Co-Authors: Jeum Kyu Hong, Du Seok Choi, Sang Hee Kim, Young Jin Kim, Byung-kook HwangAbstract:Plant integral membrane proteins have essential roles in diverse internal and external physiological processes as signal receptors or ion transporters. The pepper CaPIMP1 gene encoding a putative integral membrane protein with four transmembrane domains was isolated and functionally characterized from pepper leaves infected with the avirulent strain Xanthomonas campestris pv. vesicatoria ( Xcv ). CaPIMP1 -green fluorescence protein (GFP) fusions localized to the plasma membrane in onion cells, as observed by confocal microscopy. CaPIMP1 was expressed in an organ-specific manner in healthy pepper plants. Infection with Xcv induced differential accumulation of CaPIMP1 transcripts in pepper leaf tissues during compatible and incompatible interactions. The function of CaPIMP1 was examined by using the virus-induced gene silencing technique in pepper plants and by overexpression in Arabidopsis . CaPIMP1 -silenced pepper plants were highly susceptible to Xcv infection and expressed lower levels of the defense-related gene CaSAR82A . CaPIMP1 overexpression ( CaPIMP1- OX) in transgenic Arabidopsis conferred enhanced resistance to P. syringae pv. tomato infection, accompanied by enhanced AtPDF1.2 gene expression. In contrast, CaPIMP1 -OX plants were highly susceptible to the biotrophic oomycete Hyaloperonospora Parasitica . Taken together, we propose that CaPIMP1 plays distinct roles in both bacterial disease resistance and oomycete disease susceptibility.
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Involvement of the Pepper Antimicrobial Protein CaAMP1 Gene in Broad Spectrum Disease Resistance
Plant physiology, 2008Co-Authors: Sung Chul Lee, In Sun Hwang, Hyong Woo Choi, Byung-kook HwangAbstract:Pathogen-inducible antimicrobial defense-related proteins have emerged as key antibiotic peptides and enzymes involved in disease resistance in plants. A novel antimicrobial protein gene, CaAMP1 (for Capsicum annuum ANTIMICROBIAL PROTEIN1), was isolated from pepper (C. annuum) leaves infected with Xanthomonas campestris pv vesicatoria. Expression of the CaAMP1 gene was strongly induced in pepper leaves not only during pathogen infection but also after exposure to abiotic elicitors. The purified recombinant CaAMP1 protein possessed broad-spectrum antimicrobial activity against phytopathogenic bacteria and fungi. CaAMP1:smGFP fusion protein was localized mainly in the external and intercellular regions of onion (Allium cepa) epidermal cells. The virus-induced gene silencing technique and gain-of-function transgenic plants were used to determine the CaAMP1 gene function in plant defense. Silencing of CaAMP1 led to enhanced susceptibility to X. campestris pv vesicatoria and Colletotrichum coccodes infection, accompanied by reduced PATHOGENESIS-RELATED (PR) gene expression. In contrast, overexpression of CaAMP1 in Arabidopsis (Arabidopsis thaliana) conferred broad-spectrum resistance to the hemibiotrophic bacterial pathogen Pseudomonas syringae pv tomato, the biotrophic oomycete Hyaloperonospora Parasitica, and the fungal necrotrophic pathogens Fusarium oxysporum f. sp. matthiolae and Alternaria brassicicola. CaAMP1 overexpression induced the salicylic acid pathway-dependent genes PR1 and PR5 but not the jasmonic acid-dependent defense gene PDF1.2 during P. syringae pv tomato infection. Together, these results suggest that the antimicrobial CaAMP1 protein is involved in broad-spectrum resistance to bacterial and fungal pathogen infection.
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Pepper pectin methylesterase inhibitor protein CaPMEI1 is required for antifungal activity, basal disease resistance and abiotic stress tolerance
Planta, 2008Co-Authors: Kee Hoon Sohn, Hyong Woo Choi, In Sun Hwang, Sung Chul Lee, Byung-kook HwangAbstract:Pectin is one of the main components of the plant cell wall that functions as the primary barrier against pathogens. Among the extracellular pectinolytic enzymes, pectin methylesterase (PME) demethylesterifies pectin, which is secreted into the cell wall in a highly methylesterified form. Here, we isolated and functionally characterized the pepper ( Capsicum annuum L.) gene CaPMEI1 , which encodes a pectin methylesterase inhibitor protein (PMEI), in pepper leaves infected by Xanthomonas campestris pv. vesicatoria ( Xcv ). CaPMEI1 transcripts are localized in the xylem of vascular bundles in leaf tissues, and pathogens and abiotic stresses can induce differential expression of this gene. Purified recombinant CaPMEI1 protein not only inhibits PME, but also exhibits antifungal activity against some plant pathogenic fungi. Virus-induced gene silencing of CaPMEI1 in pepper confers enhanced susceptibility to Xcv , accompanied by suppressed expression of some defense-related genes. Transgenic Arabidopsis CaPMEI1 -overexpression lines exhibit enhanced resistance to Pseudomonas syringae pv. tomato , mannitol and methyl viologen, but not to the biotrophic pathogen Hyaloperonospora Parasitica . Together, these results suggest that CaPMEI1 , an antifungal protein, may be involved in basal disease resistance, as well as in drought and oxidative stress tolerance in plants.
Aaron Maxwell - One of the best experts on this subject based on the ideXlab platform.
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pathogens on wild radish raphanus raphanistrum brassicaceae in south western australia implications for biological control
Australasian Plant Pathology, 2008Co-Authors: Aaron Maxwell, John K ScottAbstract:Biological control options for wild radish (Raphanus raphanistrum L.) were explored through a pathogen survey in south-western Australia, inoculation studies and a literature review. Twelve fungal species were isolated from diseased wild radish, including an undescribed species of Mycosphaerella and Hyaloperonospora Parasitica, which have not been previously recorded on wild radish in Western Australia. H. Parasitica was the most damaging and widespread pathogen of wild radish. Phylogenetic analysis based on the internal transcribed spacer regions of the rRNA genes showed that the H. Parasitica isolates from wild radish are genetically distinct from the isolates found on Brassica species including canola. This finding opens up the possibility of developing a conservation or augmentative approach to the biological control of wild radish using H. Parasitica. The possibility of using other pathogens in a biocontrol strategy is remote because of likely nontarget effects on canola. Leptosphaeria biglobosa and L. maculans were widespread pathogens of wild radish suggesting this weed may provide an inoculum source for blackleg disease on canola (Brassica napus) by providing a bridge to disease along roadsides and paddocks throughout grain-growing areas.
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Pathogens on wild radish, Raphanus raphanistrum (Brassicaceae), in south-western Australia — implications for biological control
Australasian Plant Pathology, 2008Co-Authors: Aaron Maxwell, John K ScottAbstract:Biological control options for wild radish (Raphanus raphanistrum L.) were explored through a pathogen survey in south-western Australia, inoculation studies and a literature review. Twelve fungal species were isolated from diseased wild radish, including an undescribed species of Mycosphaerella and Hyaloperonospora Parasitica, which have not been previously recorded on wild radish in Western Australia. H. Parasitica was the most damaging and widespread pathogen of wild radish. Phylogenetic analysis based on the internal transcribed spacer regions of the rRNA genes showed that the H. Parasitica isolates from wild radish are genetically distinct from the isolates found on Brassica species including canola. This finding opens up the possibility of developing a conservation or augmentative approach to the biological control of wild radish using H. Parasitica. The possibility of using other pathogens in a biocontrol strategy is remote because of likely nontarget effects on canola. Leptosphaeria biglobosa and L. maculans were widespread pathogens of wild radish suggesting this weed may provide an inoculum source for blackleg disease on canola (Brassica napus) by providing a bridge to disease along roadsides and paddocks throughout grain-growing areas.
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Opportunities for the Control of Brassicaceous Weeds of Cropping Systems Using Mycoherbicides
Advances in Botanical Research, 2005Co-Authors: Aaron Maxwell, John K ScottAbstract:Mycoherbicides offer another option in controlling weeds, especially in light of increasing problems with herbicide resistance. Wild radish is a weed of cropping systems for which pathogens found in Australia include a suite of species with differing host range that could be developed into mycoherbicides useful against weed species from the Brassicaceae. Potentially useful fungal pathogens found in Australia are Alternaria alternata, A. brassicae, A. brassicicola, A. japonica, Fusarium oxysporum, and Hyaloperonospora Parasitica. Mycoherbicide candidates are considered in terms of their host specificity, virulence, epidemiological properties, industrial scale inoculum production, and suitability for liquid or solid formulation. Another critical issue is how to avoid nontarget damage in crops of the Brassicaceae such as canola. Hyaloperonospora Parasitica has potentially the most specific pathovars for the control of wild radish, but is not well suited for mycoherbicide production. Whereas Alternaria japonica is less host specific than H. Parasitica, it is probably the most suited for development as a mycoherbicide. This review identifies opportunities to overcome some of the limitations associated with delivering reliable bioherbicide technology through improved identification of pathogens associated with Brassicaceae, a better understanding of their epidemiology, and possible modifications to improve their mycoherbicide potential.
B A Kunz - One of the best experts on this subject based on the ideXlab platform.
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UV-Induced DNA Damage Promotes Resistance to the Biotrophic Pathogen Hyaloperonospora Parasitica in Arabidopsis
PLANT PHYSIOLOGY, 2008Co-Authors: B A Kunz, P. K. Dando, D. M. Grice, P. G. Mohr, P. M. Schenk, D. M. CahillAbstract:Plant innate immunity to pathogenic microorganisms is activated in response to recognition of extracellular or intracellular pathogen molecules by transmembrane receptors or resistance proteins, respectively. The defense signaling pathways share components with those involved in plant responses to UV radiation, which can induce expression of plant genes important for pathogen resistance. Such intriguing links suggest that UV treatment might activate resistance to pathogens in normally susceptible host plants. Here, we demonstrate that pre-inoculative UV (254 nm) irradiation of Arabidopsis (Arabidopsis thaliana) susceptible to infection by the biotrophic oomycete Hyaloperonospora Parasitica, the causative agent of downy mildew, induces dose- and time-dependent resistance to the pathogen detectable up to 7 d after UV exposure. Limiting repair of UV photoproducts by postirradiation incubation in the dark, or mutational inactivation of cyclobutane pyrimidine dimer photolyase, (6-4) photoproduct photolyase, or nucleotide excision repair increased the magnitude of UV-induced pathogen resistance. In the absence of treatment with 254-nm UV, plant nucleotide excision repair mutants also defective for cyclobutane pyrimidine dimer or (6-4) photoproduct photolyase displayed resistance to H. Parasitica, partially attributable to short wavelength UV-B (280-320 nm) radiation emitted by incubator lights. These results indicate UV irradiation can initiate the development of resistance to H. Parasitica in plants normally susceptible to the pathogen and point to a key role for UV-induced DNA damage. They also suggest UV treatment can circumvent the requirement for recognition of H. Parasitica molecules by Arabidopsis proteins to activate an immune response.
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UV induces resistance in Arabidopsis Thaliana to the Oomycete Pathogen Hyaloperonospora Parasitica
2006Co-Authors: D. M. Cahill, B A Kunz, P. Dando, D. Grice, B. Wade, K. MckenzieAbstract:Owing to their sessile nature, plants have evolved mechanisms to minimise the damaging effects of abiotic and biotic stresses. Attack by pathogenic fungi, viruses and bacterium is a major type of biotic stress. To resist infection, plants recognise invading pathogens and induce disease resistance through multiple signal transduction pathways. In addition, appropriate stimulation can cause plants to increase their resistance to future pathogen attack. We have found that exposure to non-lethal doses of UV-C (254 nm) renders a normally susceptible ecotype of Arabidopsis thaliana resistant to the biotrophic Oomycete pathogen Hyaloperonospora Parasitica. The UV treatment induces an incompatible response in a dose-dependent fashion, and is still effective upon pathogen inoculation up to seven days after UV exposure. The degree of resistance diminishes with time but higher doses result in greater levels of resistance, even after seven days. Furthermore, the effect is systemic, occurring in parts of the plant that have not been irradiated. Incubation in the dark post?irradiation and prior to infection reduces the UV dose required to generate a specific level of pathogen resistance without affecting the duration of resistance. These observations, plus the inability of plants to photoreactivate UV photoproducts in the dark, strongly suggest that DNA damage induces the resistance phenotype. Currently, we are assessing the influence of DNA repair defects on UV-induced resistance, following the expression of a number of defence?related genes post-UV-C irradiation, and assessing the effect of UV in plant mutants deficient in specific signalling molecules involved in resistance.
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DNA repair deficiencies increase the resistance of Arabidopsis Thaliana to Hyaloperonospora Parasitica
2006Co-Authors: D. Grice, P. G. Mohr, B A Kunz, P. Dando, B. Wade, K. Mckenzie, D. M. CahillAbstract:We have found that UV-C treatment of Arabidopsis thaliana induces resistance to the biotrophic pathogen Hyaloperonospora Parasitica, and our data suggest UV induced DNA photoproducts are involved (see accompanying abstract by K.G. McKenzie et al.). To address the potential role of DNA damage, we have examined the effect of mutations in nucleotide excision repair (uvr1-1), photoreactivation of cyclobutane pyrimidine dimers (uvr2-1) or flavonoid production (tt5) on the resistance of Arabidopsis to the pathogen with or without pre-inoculation treatment with UV-C. In the mutant backgrounds, UV-C induced pathogen resistance (as measured by decreased conidiophore formation) to the same degree as in the wildtype plants, but much lower UV doses were required (e.g., 100 Jm-2 in the mutant vs. 400 Jm-2 in the wildtype). This is the result expected if damage to DNA rather than a non DNA target is involved. Interestingly, in the absence of UV-C, the tt5 mutation alone resulted in a slight increase in resistance. However, when coupled with uvr1-1, resistance was enhanced to an even greater extent. Remarkably, the tt5 uvr1-1 uvr2-1 triple mutant was completely resistant to the pathogen. Since tt5 mutants are sensitive to reactive oxygen species, which can cause DNA damage susceptible to nucleotide excision repair, our results suggest that in addition to UV photoproducts, an accumulation of endogenous oxidative DNA damage may also trigger resistance to the pathogen. We are currently examining pathogen resistance in other DNA repair deficient mutants, and quantifying UV-C-induced DNA damage in Arabidopsis in order to assess the relationship between damage levels and the extent of resistance.
