Iron is an essential component of various proteins and pigments for both plants and pathogenic fungi. However, redox cycling between the ferric and ferrous forms of iron can also catalyse the production of dangerous free radicals and iron homeostasis is therefore tightly regulated. During pathogen attack, plants quickly produce large amounts of reactive oxygen species at the site of attempted pathogen ingress. This so-called oxidative burst has received considerable attention, but no single enzyme has been shown to account for the phenomenon. Using inductively coupled plasma mass spectrometry and histochemistry, I show that iron is secreted to the apoplast of the diploid wheat <i>Triticum monococcum</i> during attack by the powdery mildew fungus <i>Blumeria graminis</i> f.sp. <i>tritici</i>. This iron accumulates at cell wall appositions synthesised de novo beneath sites of pathogen attack. I further show, using histochemistry and pharmaceutical inhibitors, that this apoplastic iron accumulation is required for production of H2O2 in the oxidative burst. To understand the impact of this massive change in iron homeostasis on gene transcription, I employ a 187 gene targeted macroarray platform and establish that iron overload induces the expression of iron homeostasis-related genes and defence-related genes through iron itself and iron-mediated H2O2 production, respectively. To illustrate how the plant is able to withstand the negative effects of its own oxidative defences, I characterise a novel quinone redox cycle, and show that simultaneous induction of a protective quinone reductase isoform and downregulation of reactive oxygen-producing quinone reductase isoform prevents the spread of reactive oxygen during pathogen attack. Finally, in an effort to understand the impact of iron on fungal pathogenicity, I investigate iron uptake in the head blight pathogen, <i>Fusarium graminearum</i>. Fungi use at least two separate systems to take up iron, one based on enzymatic iron reduction and the other based on the synthesis and secretion of small iron chelators termed siderophores. Using mutants disrupted in either of two modes of iron uptake, I establish that siderophore production is essential for full F. graminearum virulence on wheat. This thesis exposes iron as an important component of both plant defence and fungal virulence.

Iron is an essential component of various proteins and pigments for both plants and pathogenic fungi. However, redox cycling between the ferric and ferrous forms of iron can also catalyse the production of dangerous free radicals and iron homeostasis is therefore tightly regulated. During pathogen attack, plants quickly produce large amounts of reactive oxygen species at the site of attempted pathogen ingress. This so-called oxidative burst has received considerable attention, but no single enzyme has been shown to account for the phenomenon. Using inductively coupled plasma mass spectrometry and histochemistry, I show that iron is secreted to the apoplast of the diploid wheat <i>Triticum monococcum</i> during attack by the powdery mildew fungus <i>Blumeria graminis</i> f.sp. <i>tritici</i>. This iron accumulates at cell wall appositions synthesised de novo beneath sites of pathogen attack. I further show, using histochemistry and pharmaceutical inhibitors, that this apoplastic iron accumulation is required for production of H2O2 in the oxidative burst. To understand the impact of this massive change in iron homeostasis on gene transcription, I employ a 187 gene targeted macroarray platform and establish that iron overload induces the expression of iron homeostasis-related genes and defence-related genes through iron itself and iron-mediated H2O2 production, respectively. To illustrate how the plant is able to withstand the negative effects of its own oxidative defences, I characterise a novel quinone redox cycle, and show that simultaneous induction of a protective quinone reductase isoform and downregulation of reactive oxygen-producing quinone reductase isoform prevents the spread of reactive oxygen during pathogen attack. Finally, in an effort to understand the impact of iron on fungal pathogenicity, I investigate iron uptake in the head blight pathogen, <i>Fusarium graminearum</i>. Fungi use at least two separate systems to take up iron, one based on enzymatic iron reduction and the other based on the synthesis and secretion of small iron chelators termed siderophores. Using mutants disrupted in either of two modes of iron uptake, I establish that siderophore production is essential for full F. graminearum virulence on wheat. This thesis exposes iron as an important component of both plant defence and fungal virulence.

Equine infectious anemia virus (EIAV) causes rapid development of acute disease followed by recurring episodes of fever, thrombocytopenia and viremia, termed chronic EIA. Most infected horses control the virus by immune mechanisms and become inapparent carriers. To further our understanding of the equine immune response to EIAV, a multi-probe ribonuclease protection assay (RPA) was developed to quantitate equine-specific cytokine mRNAs. Eleven template plasmids specific to ten equine cytokine genes and the ?-actin gene were generated, from which radiolabeled anti-sense RNA probes were produced. The RPA simultaneously quantitated mRNA levels of interleukin (IL)-1, IL-1, IL-6, IL-8, IL-10, IL-12 p35, IL-12 p40, interferon (IFN)-, transforming growth factor (TGF)-1 and tumor necrosis factor (TNF)- in equine peripheral blood mononuclear cells and equine monocyte-derived macrophages (EMDM). The assay detected as few as 5105 RNA molecules and displayed coefficients of variation of 0.03-0.08 when normalized to -actin expression. Using this RPA, cytokine expression in EMDM infected with 2 molecularly cloned viruses (EIAV17 and EIAV19) was determined. EIAV17 varies from EIAV19 only in env, rev and LTR and causes fatal disease in Shetland ponies. When added to EMDM cultures, virulent EIAV17 stimulated expression of IL-1, IL-1, IL-6, IL-10 and TNF-. These cytokine mRNAs were significantly elevated by 0.5 to 1 hr post infection (hpi) and returned to basal levels by 12 to 24 hpi, indicating modulation by early event(s), such as receptor binding. In contrast to EIAV17, EIAV19 is avirulent in vivo and failed to induce any of the tested cytokines in EMDM. These data show a direct correlation between the virulence of the EIAV clone and the induction of cytokines. The cytokines stimulated by EIAV17 may contribute to EIA-associated symptoms, enhance viral replication in the host, and regulate the host immune response. To determine whether cytokine induction requires EIAV17 replication, EMDM cultures were exposed to UV-inactivated EIAV17 and cytokine induction was monitored. UV-inactivation did not block cytokine induction by EIAV17, suggesting dispensability of viral replication. Given that EIAV17 induces cytokines in a rapid and replication-independent manner, the activation of cytokine expression is likely mediated by binding of EIAV17 to equine macrophage receptor(s).

Thesis (Ph. D.)--Cornell University, August, 2006. / Vita. Includes bibliographical references (leaves 201-220).

Reproduction de : Thèse de doctorat : Sciences vétérinaires : Toulouse, INPT : 2005. / Titre provenant de l'écran-titre. Bibliogr. 216 réf.

Reproduction de : Thèse doctorat : Médecine. Biologie cellulaire : Reims : 2006. / Titre provenant de l'écran-titre. Bibliogr. p.140-158.

Thesis (Ph.D.) -- University of Adelaide, School of Molecular and Biomedical Science, Discipline of Microbiology and Immunology, 2008. / Includes "Thesis Amendments" attached to the inside back pages. "October 2007" Bibliography: leaves 108-121. Also available in print form.

Thesis (Ph. D.)--University of Missouri--Columbia, 2001. / "August 2001." Typescript. Vita. Includes bibliographical references (leaves 96-103). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri--Columbia, 2001. / Typescript. Vita. Includes bibliographical references (leaves 96-103). Also available on the Internet.

Thesis (Ph. D.)--Ohio State University, 2003. / Title from first page of PDF file. Document formatted into pages; contains xvi, 134 p. : ill., (some col.). Includes abstract and vita. Advisor: Kathryn A. Eaton, Dept. of Veterinary Biosciences. Includes bibliographical references (p. 107-134).