CYTOLOGICAL AND CYTOCHEMICAL OBSERVATIONS ON THE EARLY STAGE OF INFECTION OF TOMATO HAIR CELLS BY TOBACCO MOSAIC VIRUS

Strips of epidermal tissue bearing hair cells were removed fromtomato stems. The lower surface exposed by the stripping wasinoculated with tobacco mosaic virus and the progress of infectionof the hair cells was followed microscopically and by extractionof infectivity. Shortly before infectivity could be extractedfrom the hair cells, the nuclei were observed to have migratedtowards the tran sverse wall of the basal hair cell nearestthe epidermis, apparently the site at which infection of thecell commences. After infection was apparent, the staining characteristicsof the nuclei, before and after RNase and DNase treatment, suggestedan accumulation of RNA. A granular body, different from X-bodiesmaintained a close association with the nucleus of TMV infectedhair cells, and was found to be rich in RNA, suggesting thatviral RNA of the nucleus may have been entering the cytoplasmvia the granular body. A possible mechanism of X-body formationarising from the granular body is suggested. ¹ Supported in part by a grant E-536 (C9) from the U. S. PublicHealth Service.² Present address: Plant Pathology Laboratory, Faculty of Agriculture,Nagoya University, Anjo, Aichi (Japan). (Received March 4, 1963; )