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The Origin, Development, and Conformation of Amorphous Inclusion Body Components in Tobacco Etch Virus-Infected Cells. John H. Andrews, Department of Plant Pathology, University of California, Davis 95616, Present address of senior author: A.R.C. Unit of Developmental Botany, University of Cambridge, Cambridge, CB3 ODY England.; T. A. Shalla, Department of Plant Pathology, University of California, Davis 95616. Phytopathology 64:1234-1243. Accepted for publication 30 April 1974. DOI: 10.1094/Phyto-64-1234.

The origin, development, and conformation of pinwheel inclusion bodies induced by tobacco etch virus (TEV) were studied in tobacco (Nicotiana tabacum L. ‘Havana 425’) root tips. Pinwheels were abutted to cell walls at plasmodesmata in cells examined during the early stages of infection. With time, there was an increasing tendency for pinwheels to be located free in the cytoplasm and to have more and longer arms, fused arms, and opened central cores. Pinwheel arms appeared triangular when examined in serial sections. On the basis of results obtained by freeze-etching and the use of different fixatives, it was concluded that pinwheels are real entities, not artifacts of sample preparation. Evidence is presented to show that they originate at plasmodesmata and may be released into the cytoplasm at a later stage of development, and that the inclusion as a whole is conically shaped, at least during the early stages of formation.