Oligogalacturonide signalling in plant innate immunity

Pär Roland Davidsson

Forskningsoutput: AvhandlingDoktorsavhandlingSamling av artiklar

Sammanfattning

Necrotrophic phytopathogens, such as soft rot bacteria, cause large losses in agriculture. Unlike biotrophic pathogens, these typically rely on toxins and plant cell wall-degrading enzymes (PCWDEs) to kill and degrade the host tissue. As such, the methods utilised by the plants to defend themselves against biotrophs, such as the hypersensitivity response (HR), could instead be beneficial for necrotrophic pathogens. One key component in plant defence against necrotrophic pathogens is the recognition of oligogalacturonides (OGs), a breakdown product of the pectin in the plant cell wall, formed by the action of PCWDEs. Similar to direct recognition of the pathogen itself, recognition of OGs trigger a wide array of defence responses, resulting in improved protection against pathogens. Long OGs with a degree of polymerisation (DP) between 10 and 20 have been well studied. In this study, we explored the role of the relatively less understood short OGs (DP < 9). We utilised trimeric OGs to study the changes induced by short OGs on the transcriptome of Arabidopsis thaliana. We established that, similarly to long OGs, short OGs up-regulate genes related to defence and down-regulate genes related to plant growth and development. Phenotypic assays confirmed that pre-treatment with short OGs could improve resistance in A. thaliana against the soft rot bacteria Pectobacterium carotovorum, to the same degree as long OGs. Furthermore, we showed that treatment with both types of OGs results in seedling growth retardation. As part of investigating the signalling triggered by short OGs, we confirmed that trimeric OGs do not trigger the characteristic initial ROS (reactive oxygen species) burst, but do trigger expression of a large set of peroxidases. Similar to long OGs, part of the signalling in response to short OGs goes via phosphorylation of Mitogen-activated protein kinases (MAPKs). Our results show that short OGs are indeed biologically active elicitors of plant defence, with a signalling pathway that appears to be in part distinct from long OG signalling. We used the established trade-off between plant defence and plant growth and development to develop screens for mutants with altered OG sensitivity. One mutant line exhibiting hypersensitivity to OGs, resistance to the necrotrophic pathogens Botrytis cinerea and P. carotovorum, as well as sensitivity to the hemibiotrophic pathogen Pseudomonas syringae, was chosen for further studies. We established that the observed phenotypes were due to overexpression a cell wall-localised apoplastic peroxidase (class III peroxidase, CIII Prx) – PEROXIDASE 57 (PER57). We detected increased levels of ROS and increased cuticle permeability, associated with downregulation of genes involved in cutin formation and biosynthesis. We also observed a priming of OG related response genes. The phenotypes could be recaptured by overexpression of several CIII Prxs, indicating a general phenomenon. ABA treatment of these lines restored the phenotypes to wild-type. This appears to be mediated via removal of ROS. Noticeably, the peroxidase activity remained high in the peroxidase overexpression lines, indicating that while exogenous application of ABA was able to remove the ROS produced by the peroxidases it only had a minor direct effect on the activity of the peroxidases. Our results, combined with previous research on cuticular and ABA mutants, led us to propose that cuticle integrity is influenced by a positive feed-back loop. A disturbed cuticle leads to elevated ROS levels via increased peroxidase activity, which in turn impairs cuticle formation and biosynthesis. Under normal circumstances this loop is regulated by ABA. In the situation where a necrotrophic pathogen is invading the plant recognition of cell-wall derived DAMPs, such as OGs, it leads to activation of peroxidases that further promote resistance signalling via the creation of ROS.
Originalspråkengelska
Tilldelande institution
  • Helsingfors universitet
Handledare
  • Palva, E. Tapio, Handledare
Tilldelningsdatum30 jun 2017
UtgivningsortHelsinki
Förlag
Tryckta ISBN978-951-51-3526-1
Elektroniska ISBN978-951-51-3527-8
StatusPublicerad - 30 jun 2017
MoE-publikationstypG5 Doktorsavhandling (artikel)

Vetenskapsgrenar

  • 1183 Växtbiologi, mikrobiologi, virologi
  • 1184 Genetik, utvecklingsbiologi, fysiologi
  • 1182 Biokemi, cell- och molekylärbiologi

Citera det här

Davidsson, P. R. (2017). Oligogalacturonide signalling in plant innate immunity. Helsinki: University of Helsinki.
Davidsson, Pär Roland. / Oligogalacturonide signalling in plant innate immunity. Helsinki : University of Helsinki, 2017. 46 s.
@phdthesis{7a59f98740ff4eb899579568d01d9ecc,
title = "Oligogalacturonide signalling in plant innate immunity",
abstract = "Necrotrophic phytopathogens, such as soft rot bacteria, cause large losses in agriculture. Unlike biotrophic pathogens, these typically rely on toxins and plant cell wall-degrading enzymes (PCWDEs) to kill and degrade the host tissue. As such, the methods utilised by the plants to defend themselves against biotrophs, such as the hypersensitivity response (HR), could instead be beneficial for necrotrophic pathogens. One key component in plant defence against necrotrophic pathogens is the recognition of oligogalacturonides (OGs), a breakdown product of the pectin in the plant cell wall, formed by the action of PCWDEs. Similar to direct recognition of the pathogen itself, recognition of OGs trigger a wide array of defence responses, resulting in improved protection against pathogens. Long OGs with a degree of polymerisation (DP) between 10 and 20 have been well studied. In this study, we explored the role of the relatively less understood short OGs (DP < 9). We utilised trimeric OGs to study the changes induced by short OGs on the transcriptome of Arabidopsis thaliana. We established that, similarly to long OGs, short OGs up-regulate genes related to defence and down-regulate genes related to plant growth and development. Phenotypic assays confirmed that pre-treatment with short OGs could improve resistance in A. thaliana against the soft rot bacteria Pectobacterium carotovorum, to the same degree as long OGs. Furthermore, we showed that treatment with both types of OGs results in seedling growth retardation. As part of investigating the signalling triggered by short OGs, we confirmed that trimeric OGs do not trigger the characteristic initial ROS (reactive oxygen species) burst, but do trigger expression of a large set of peroxidases. Similar to long OGs, part of the signalling in response to short OGs goes via phosphorylation of Mitogen-activated protein kinases (MAPKs). Our results show that short OGs are indeed biologically active elicitors of plant defence, with a signalling pathway that appears to be in part distinct from long OG signalling. We used the established trade-off between plant defence and plant growth and development to develop screens for mutants with altered OG sensitivity. One mutant line exhibiting hypersensitivity to OGs, resistance to the necrotrophic pathogens Botrytis cinerea and P. carotovorum, as well as sensitivity to the hemibiotrophic pathogen Pseudomonas syringae, was chosen for further studies. We established that the observed phenotypes were due to overexpression a cell wall-localised apoplastic peroxidase (class III peroxidase, CIII Prx) – PEROXIDASE 57 (PER57). We detected increased levels of ROS and increased cuticle permeability, associated with downregulation of genes involved in cutin formation and biosynthesis. We also observed a priming of OG related response genes. The phenotypes could be recaptured by overexpression of several CIII Prxs, indicating a general phenomenon. ABA treatment of these lines restored the phenotypes to wild-type. This appears to be mediated via removal of ROS. Noticeably, the peroxidase activity remained high in the peroxidase overexpression lines, indicating that while exogenous application of ABA was able to remove the ROS produced by the peroxidases it only had a minor direct effect on the activity of the peroxidases. Our results, combined with previous research on cuticular and ABA mutants, led us to propose that cuticle integrity is influenced by a positive feed-back loop. A disturbed cuticle leads to elevated ROS levels via increased peroxidase activity, which in turn impairs cuticle formation and biosynthesis. Under normal circumstances this loop is regulated by ABA. In the situation where a necrotrophic pathogen is invading the plant recognition of cell-wall derived DAMPs, such as OGs, it leads to activation of peroxidases that further promote resistance signalling via the creation of ROS.",
keywords = "1183 Plant biology, microbiology, virology, 1184 Genetics, developmental biology, physiology, 1182 Biochemistry, cell and molecular biology",
author = "Davidsson, {P{\"a}r Roland}",
year = "2017",
month = "6",
day = "30",
language = "English",
isbn = "978-951-51-3526-1",
series = "Dissertationes Schola Doctoralis Scientiae Circumiectalis, Alimentariae, Biologicae",
publisher = "University of Helsinki",
number = "15/2017",
address = "Finland",
school = "University of Helsinki",

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Davidsson, PR 2017, 'Oligogalacturonide signalling in plant innate immunity', Helsingfors universitet, Helsinki.

Oligogalacturonide signalling in plant innate immunity. / Davidsson, Pär Roland.

Helsinki : University of Helsinki, 2017. 46 s.

Forskningsoutput: AvhandlingDoktorsavhandlingSamling av artiklar

TY - THES

T1 - Oligogalacturonide signalling in plant innate immunity

AU - Davidsson, Pär Roland

PY - 2017/6/30

Y1 - 2017/6/30

N2 - Necrotrophic phytopathogens, such as soft rot bacteria, cause large losses in agriculture. Unlike biotrophic pathogens, these typically rely on toxins and plant cell wall-degrading enzymes (PCWDEs) to kill and degrade the host tissue. As such, the methods utilised by the plants to defend themselves against biotrophs, such as the hypersensitivity response (HR), could instead be beneficial for necrotrophic pathogens. One key component in plant defence against necrotrophic pathogens is the recognition of oligogalacturonides (OGs), a breakdown product of the pectin in the plant cell wall, formed by the action of PCWDEs. Similar to direct recognition of the pathogen itself, recognition of OGs trigger a wide array of defence responses, resulting in improved protection against pathogens. Long OGs with a degree of polymerisation (DP) between 10 and 20 have been well studied. In this study, we explored the role of the relatively less understood short OGs (DP < 9). We utilised trimeric OGs to study the changes induced by short OGs on the transcriptome of Arabidopsis thaliana. We established that, similarly to long OGs, short OGs up-regulate genes related to defence and down-regulate genes related to plant growth and development. Phenotypic assays confirmed that pre-treatment with short OGs could improve resistance in A. thaliana against the soft rot bacteria Pectobacterium carotovorum, to the same degree as long OGs. Furthermore, we showed that treatment with both types of OGs results in seedling growth retardation. As part of investigating the signalling triggered by short OGs, we confirmed that trimeric OGs do not trigger the characteristic initial ROS (reactive oxygen species) burst, but do trigger expression of a large set of peroxidases. Similar to long OGs, part of the signalling in response to short OGs goes via phosphorylation of Mitogen-activated protein kinases (MAPKs). Our results show that short OGs are indeed biologically active elicitors of plant defence, with a signalling pathway that appears to be in part distinct from long OG signalling. We used the established trade-off between plant defence and plant growth and development to develop screens for mutants with altered OG sensitivity. One mutant line exhibiting hypersensitivity to OGs, resistance to the necrotrophic pathogens Botrytis cinerea and P. carotovorum, as well as sensitivity to the hemibiotrophic pathogen Pseudomonas syringae, was chosen for further studies. We established that the observed phenotypes were due to overexpression a cell wall-localised apoplastic peroxidase (class III peroxidase, CIII Prx) – PEROXIDASE 57 (PER57). We detected increased levels of ROS and increased cuticle permeability, associated with downregulation of genes involved in cutin formation and biosynthesis. We also observed a priming of OG related response genes. The phenotypes could be recaptured by overexpression of several CIII Prxs, indicating a general phenomenon. ABA treatment of these lines restored the phenotypes to wild-type. This appears to be mediated via removal of ROS. Noticeably, the peroxidase activity remained high in the peroxidase overexpression lines, indicating that while exogenous application of ABA was able to remove the ROS produced by the peroxidases it only had a minor direct effect on the activity of the peroxidases. Our results, combined with previous research on cuticular and ABA mutants, led us to propose that cuticle integrity is influenced by a positive feed-back loop. A disturbed cuticle leads to elevated ROS levels via increased peroxidase activity, which in turn impairs cuticle formation and biosynthesis. Under normal circumstances this loop is regulated by ABA. In the situation where a necrotrophic pathogen is invading the plant recognition of cell-wall derived DAMPs, such as OGs, it leads to activation of peroxidases that further promote resistance signalling via the creation of ROS.

AB - Necrotrophic phytopathogens, such as soft rot bacteria, cause large losses in agriculture. Unlike biotrophic pathogens, these typically rely on toxins and plant cell wall-degrading enzymes (PCWDEs) to kill and degrade the host tissue. As such, the methods utilised by the plants to defend themselves against biotrophs, such as the hypersensitivity response (HR), could instead be beneficial for necrotrophic pathogens. One key component in plant defence against necrotrophic pathogens is the recognition of oligogalacturonides (OGs), a breakdown product of the pectin in the plant cell wall, formed by the action of PCWDEs. Similar to direct recognition of the pathogen itself, recognition of OGs trigger a wide array of defence responses, resulting in improved protection against pathogens. Long OGs with a degree of polymerisation (DP) between 10 and 20 have been well studied. In this study, we explored the role of the relatively less understood short OGs (DP < 9). We utilised trimeric OGs to study the changes induced by short OGs on the transcriptome of Arabidopsis thaliana. We established that, similarly to long OGs, short OGs up-regulate genes related to defence and down-regulate genes related to plant growth and development. Phenotypic assays confirmed that pre-treatment with short OGs could improve resistance in A. thaliana against the soft rot bacteria Pectobacterium carotovorum, to the same degree as long OGs. Furthermore, we showed that treatment with both types of OGs results in seedling growth retardation. As part of investigating the signalling triggered by short OGs, we confirmed that trimeric OGs do not trigger the characteristic initial ROS (reactive oxygen species) burst, but do trigger expression of a large set of peroxidases. Similar to long OGs, part of the signalling in response to short OGs goes via phosphorylation of Mitogen-activated protein kinases (MAPKs). Our results show that short OGs are indeed biologically active elicitors of plant defence, with a signalling pathway that appears to be in part distinct from long OG signalling. We used the established trade-off between plant defence and plant growth and development to develop screens for mutants with altered OG sensitivity. One mutant line exhibiting hypersensitivity to OGs, resistance to the necrotrophic pathogens Botrytis cinerea and P. carotovorum, as well as sensitivity to the hemibiotrophic pathogen Pseudomonas syringae, was chosen for further studies. We established that the observed phenotypes were due to overexpression a cell wall-localised apoplastic peroxidase (class III peroxidase, CIII Prx) – PEROXIDASE 57 (PER57). We detected increased levels of ROS and increased cuticle permeability, associated with downregulation of genes involved in cutin formation and biosynthesis. We also observed a priming of OG related response genes. The phenotypes could be recaptured by overexpression of several CIII Prxs, indicating a general phenomenon. ABA treatment of these lines restored the phenotypes to wild-type. This appears to be mediated via removal of ROS. Noticeably, the peroxidase activity remained high in the peroxidase overexpression lines, indicating that while exogenous application of ABA was able to remove the ROS produced by the peroxidases it only had a minor direct effect on the activity of the peroxidases. Our results, combined with previous research on cuticular and ABA mutants, led us to propose that cuticle integrity is influenced by a positive feed-back loop. A disturbed cuticle leads to elevated ROS levels via increased peroxidase activity, which in turn impairs cuticle formation and biosynthesis. Under normal circumstances this loop is regulated by ABA. In the situation where a necrotrophic pathogen is invading the plant recognition of cell-wall derived DAMPs, such as OGs, it leads to activation of peroxidases that further promote resistance signalling via the creation of ROS.

KW - 1183 Plant biology, microbiology, virology

KW - 1184 Genetics, developmental biology, physiology

KW - 1182 Biochemistry, cell and molecular biology

M3 - Doctoral Thesis

SN - 978-951-51-3526-1

T3 - Dissertationes Schola Doctoralis Scientiae Circumiectalis, Alimentariae, Biologicae

PB - University of Helsinki

CY - Helsinki

ER -

Davidsson PR. Oligogalacturonide signalling in plant innate immunity. Helsinki: University of Helsinki, 2017. 46 s. (Dissertationes Schola Doctoralis Scientiae Circumiectalis, Alimentariae, Biologicae; 15/2017).