Virus-induced Nucleolar Abnormalities in Tomato

Abstract

IN view of current opinions on the nature of virus particles¹, recent work carried out in this department on the effect of the ‘aspermy’ virus upon nuclear, and especially nucleolar, behaviour in plant cells may have a special significance. Caldwell² reported prophase collapse in diseased pollen- and embryo-sac mother cells in tomato, accompanied by peculiarities of nucleolar behaviour, and Wilkinson³ has observed similar meiotic abnormalities in Nicotiana glutinosa. Recent examination of somatic divisions in diseased tomato and tobacco plants has revealed the occurrence of widespread nucleolar and other abnormalities, some of which recall the aberrations regarded as typical of the cell-divisions found in malignant animal tissue; for example, arrested metaphase, collapse at metaphase, spindle malformation and breakdown, tendency to form giant nuclei, etc. In particular, abnormal persistence of the nucleolar material, and sometimes an apparent multiplication of nucleolar bodies during the mitotic cycle, have been very striking. Thus, in dividing cells of root tips obtained from tomato shoots heavily infected with the ‘aspermy’ virus, the nucleolar material, instead of dispersing during prophase, persists through anaphase in the form of one or more prominent and somewhat elongated vesicles. The accompanying photograph shows a typical dividing nucleus at early anaphase, with the nucleolar vesicle in a central position upon the somewhat distorted spindle; incidentally, in the cell above can be seen an example of metaphase collapse. Similar results have been obtained in tobacco species infected with the same virus.