Immunofluorescence studies on synthesis and distribution of tobacco mosaic virus antigen in tobacco

Abstract

Techniques were improved for obtaining fluorescein-conjugated antibodies that specifically stained tobacco mossaic virus (TMV) antigen in plant tissues. Mesophyll cells separated by pectinase digestion and paraffin sections of leaves were stained with such fluorescent antibodies to study the synthesis, distribution, and movement of TMV antigen. The latent periods after infection either with TMV or with its ribonucleic acid, as studied antigenically, or by infectivity assays on Nicotiana tabacum var. Xanthi-nc, were similar (18–24 hours) when samples were obtained at 6-hour intervals. TMV antigen was first noticed in infected mesophyll cells in the form of tiny specks of stained material which later formed a ring around the chloroplasts. No antigen was noticed within chloroplasts or nuclei of infected cells. All cell types except the primary xylem elements were susceptible to TMV infection; however, in systematically infected leaves, some mesophyll cells in the dark green areas appeared to be resistant to virus invasion. In stems adjacent to inoculated leaves, TMV antigen was first detected within the phloem and secondary xylem. In stem tips of infected plants, cells containing virus antigen were unevenly distributed. It was demonstrated that a strain of TMV hitherto believed to be a “proteinless” mutant produced TMV protein in infected cells.