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T E Role of Hydrogen Peroxide in The TEROLE OF HYDROGEN PEROXIDE IN THE RESISTANCE OF TOMATO TO PENETRATION BY COLLETOTRICHUM COCCODES inge Viia Foulds A thesis submitted in conformity with the requirements for the degree of Master of Science Graduate Deparment of Botany University of Toronto O Copyright by Inge Vüa Foulds 2000 National Library Bibliothèque nationale I*u of Canada du Canada Acquisitions and Acquisitions et Bibliographie Services services bibliographiques 395 Wellington Street 395, rue Wellington OttawaON K1AON4 OttawaON K1AON4 Canada Canada The author has granted a non- L'auteur a accordé une licence non exclusive licence ailowing the exclusive permettant à la National Library of Canada to Bibliothèque nationale du Canada de reproduce, loan, distribute or sel1 reproduire, prêter, distribuer ou copies of this thesis in rnicroform, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/filrn, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts fiom it Ni la thèse ni des extraits substantiels rnay be printed or otheMrise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. Canada THE ROLE OF HYDROGEN PEROXDE IN THE EESISTANCE OF TOMATO TO PENETRATION BY COLLETOTRICHUM COCCODES Degree of Master of Science. 2000 Inge Viia Foulds Department of Botany University of Toronto AB STRACT The accumulation of reactive oxygen species and subsequent effects were investigated in the interaction between Colletorriclinm coccodes. causai agent of anthracnose. and tomato cotyledons. Afrer initiation of penetration the fungus enters a quiescent stage and does not imrnediately colonize the host. Hydrogen peroxide (H20ù, localized with diaminobenzidine. accumulated at sites of attempted fungai penetration. in contrast, superoxide was not detected at these sites as visualized by nitroblue tetrazolium. injection of catalase or ascorbic acid into tomato cotyledons prior to inoculation. to reduce H2O2accumulation, significantly increased the frequency of fungal penetration (48 hpi) by the pathogen C. coccodes, but not the non-pathogen C. lagenarium. In the host interaction, H202accumulation was associated with cross- linking of cell wall proteins at sites of attempted penetration. Transcription and translation inhibitor treatments did not increase fungal penetration, supporting a role for oxidative cross-linking as a resistance mechanism in this interaction. First 1 would like to express thanks to my supervisor, Dr. Vema Higgins for providing me with the opportunity to work in her lab and to my supervisory cornmittee members. Dr. R.K. Carneron and Dr. M.C. Heath, for their helpful commenü and srigpshcs rhroughout the courçc of 'As nork. 1 am also grateful to Alice Cheung, who has provided much assistance over the past two years, and has always been willing to Iend a helping hand when needed. The support and friendship of other gnduate students cannot be overlooked. and I owe much thanks to Denny Mellersh for dl his assistance from day one onward. Upon her arrivai to the lab Stephanie Bordrn has also been a wonderful source of suppon. 1 must also thank Steph. Denny. and Rosemarie Chnstopher-Kozjan for their friendship and more recently for their willingness to edit my thesis. Thanks also to Tara Nanvani and Julie Kus who shared GSU duties with me over the last two yem. thus making those long meetings a more enjoyable experience. It is also important to note those outside the department who have been an important source of encouragement, 1 am greatly appreciative of the support 1 received from my parents and from Marcus. TABLE OF CONTENTS ABSTRACT ............................................................................. ACKNOWLEDGEMENTS ........................................................... CONTESTS .................,......*.....................*............... kV LIST OF FIGURES ..................................................................... vi LIST OF TABLES ...................................................................... vii LIST OF ABBREVIATIONS ......................................................... viii INTRODUCTION ...................................................................... LITERATURE REVIEW .............................................................. An Overview of Plant-Pathogen Interactions..................................... Plant Defense Responses ............................................................ Pathogenesis-Related Proteins .................................................... Reactive Oxygen Species ......................................................... Functions of the Oxidative Burst ................................................... Antimicrobial Activity ............................................................ Cell Wall Fortification .............................. ,.,, ........................... Secondary Signaling ............................................................... Colletotrichr~rncoccodes as a Plant Pathogen ..................................... Resistance Mechanisms to Colletotrichum........................................ Thesis Objectives ..................................................................... METHODS AND MATERIALS ................................... .... .............. Plant Material and Growth Conditions ............................................. Fungal Growth Conditions and Inoculation ....................................... Histological Examination ............................................................ Reactive Oxygen Species (ROS)localization ..................................... In plunta Detection of H2O2.....................................................-. In pianla Detection of O,'.. ....................................................... ROS Scavenger and Antioxidant Treatments ..................................... Inhibitor and Peptide Treatments ................................................... Tissue Prepantion for Detection of Ceil Wall Protein Cross4inking.......... Lignin Staimng ........................................................................ Statistical Analysis .................................................................... RNA Isolation ......................................................................... Northem Analysis ..................................................................... Prepamtion of Radiolabelled DNA Probes ........................................ Temporai Pattern of Reactive Oxygen Species (ROS) Accumulation ......... Effect of Transcription and Translation Inhibitors on H202Accumulation ... Effect of ROS Scavenger Treaunents.............................................. Effect of Scavenging H202After Appressorial Fowation ...................... Defense Gene Accumulation Post-Inoculation .................................... E ffect of Transcription and Translation Inhibitor Treatments.................. Effect of RGD-peptide Treatment .................................................. Cross-linking of Ce11 Wall Proteins ................................................ Absence of Lignification at Sites of Attempted Penetration .................... Accumulation of &O7 in a Nonhost Interaction ................................. Effect of Scavenging H202in a Nonhost Interaction ............................. DISCUSSION ............................................................................ REFERENCES ........................................................................... LIST OF FIGURES Figure 1. Localization of H20t at sites of attempted penetration .................. Figure 2. Frequency of HzOzaccumulation at sites of attempted peneuation (24 hpi) and the effecr of ROS scavengers on DAB staining frequency................................................ Figure 3. Frequency of H202accumulation following inoculation ............... Figure 4. Effect of transcription and translation inhibitor treatrnents on Hz02accumulation ....................................................... Figure 5. Successful penetration of tomato following anrimidant treatment ..................................................................... Figure 6. Effect of ROS scavengers on peneuation frequency.................... Figure 7 . Macroscopic symptoms of disease after a pre-inoculation cataiase treaiment ............................................................ Figure 8. Effect of cataiase treatment after appressoriai formation on the peneuation frequency ............................................... Figure 9. P4 expression in tomato cotyledons...................................... Figure 10. Effect of transcription and translation inhibitor treatments on penetration frequency.................................................. Figure 11. Effect of peptide treatments on the penetntion frequency ............. Figure 12 . Cross-linking of ce11 wall proteins at sites of attempted penemtion ................................................................. Fipre 13. Effect of catalase treatment on the frequency of ce11 wail protein cross-linking at sites of attempted penetration ............... Figure 14. Frequency of HPl accumulation at sites of attempted penetration. after inoculation with a pathogen or a non-pathogen ............................................................... Figure 15. Effect of catalase treatment on the
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