Chapter I 



The Process of Infection and Virus Synthesis with 

 Tobacco Mosaic Virus and Other Plant Viruses 



Samuel G. Wildman 

 Department of Botany, University of California, Los Angeles, California 



I. Introduction 1 



II. General Features of the Host-Virus System 2 



A. Organization of Plant Leaves 2 



B. Exclusion of Some Plant Viruses from Dividing Cells and Embryonic 

 Tissues 4 



C. Strains of Plant Viruses and Host Reactions 4 



III. Behavior of Plant Viruses in a Local Lesion Host 5 



A. Local Lesion Assay for Infectivity 5 



B. The Susceptible Site and the Initial Act of Infection 



C. Specific Infectivity of Tobacco Mosaic Virus 7 



D. What Cells Serve as Entry Ports for Virus? 8 



E. Nature of Virus Attachment at Susceptible Site 9 



E. Intracellular Development of Viruses as Deduced from Irradiation Experi- 

 ments 10 



G. Inactivation of Tobacco Mosaic Virus by Ultraviolet Light 10 



H. Changes in Virus Behavior during Early Stages of Infection 13 



I. Inactivation of Tobacco Mosaic Virus Infectious Nucleic Acid 14 



J. Spread of Infectivity from Focus of Infection 16 



K. Yield of Virus per Infected Cell 18 



L. Nature of Infectious Material 19 



;M. Is Tobacco Mosaic Virus Extracted from Lesions Identical with Tobacco 



Mosaic Virus Extracted from Systemic Hosts? 20 



IV. Behavior of Plant Viruses in a Systemic Host 21 



A. Quantities of Virus Synthesized 21 



B. Direct Observation of Virus Activity in Hair Cells 22 



C. Course of Virus Synthesis in Directly Inoculated Leaves 24 



D. Necrosis and Phloem Cells 26 



E. Effect of Virus Synthesis on Composition of Host Proteins 27 



F. X-Protem 28 



V. Summary of Steps Involved in Plant Virus Reproduction 28 



References 29 



I. Introduction 



During the 60 years since viruses were first discovered in plants, an 

 enormous literature has accumulated. The rate of accumulation was slow at 

 first. Then, in the middle 1930's, the rate took a sharp upturn as the result 



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