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Title: Molecular, genetic and biochemical dissection of defence signal transduction in Arabidopsis
Author: Aboul-Soud, Mourad A. M.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2002
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Systemic acquired resistance (SAR) is a pivotal defence response to pathogen attack that results in a broad-spectrum long-lasting immunity throughout challenged plant tissues. However, little is known about the signal transduction events leading to the establishment of SAR in plants. To facilitate the identification of novel signal transduction components that are involved in the regulation of pathogenesis-related (PR) gene expression and the establishment of SAR, we have undertaken a functional genomic approach. Chapter III, presents and describes the results obtained during the identification and characterisation of one potential mutant. Thus, homozygous Arabidopsis PR1a::luciferase transgenic lines were transformed with activation tagging vector SKI15. Hence, we generated and screened 8000 T-DNA activation tagged lines for dominant gain-of-function mutants that exhibit constitutive luciferase expression. One putative mutant was identified that exhibited high luciferase activity; constitutive HR-like lesions in the absence of pathogen; and accelerated cell death; hence it was designated potentiated cell death 1 (pcd1). Moreover, histochemical and molecular analyses revealed that pcd1 leaves accumulate high levels of hydrogen peroxide (H2O2) and constitutively express a battery of antioxidant and defence-related genes. Furthermore, biochemical analyses indicated that pcd1 plants contain high constitutive levels of the signal compound salicylic acid (SA) and elevated peroxidase and constitutive mitogen activated protein kinase (MAPK) activities. Interestingly, pcd1 plants exhibited heightened resistance against biotrophic bacterial and fungal pathogens. Importantly, epistasis analysis indicated that the HR-like lesions and H2O2 accumulation, characteristic to pcd1 phenotype, are dependent on SA but independent on ethylene and jasmonic acid. The pcd1 mutation was mapped to the lower arm of chromosome I.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available