An experimental approach to nucleolar organization in plant cells: A morphological, cytochemical and quantitative study

Abstract

ABSTRACT We have used morphological, cytochemical and immunocytochemical techniques, along with transcription inhibitors, to try to understand the nucleolar organization in Allium cepa root meristem cells. Our results reveal that the fibrillar component shows intense staining after using the NOR-silver technique, and gold particle labelling after incubation with DNase-gold and RNase-gold complexes. These different techniques reveal a reticular structure of the fibrillar component, supported by a central axis that is circular in transverse section. These structures are usually considered to be fibrillar centres, but we have called them clear areas, since we find in their interior neither Ag-NOR proteins nor labelling after incubation with nuclease-gold or anti-DNA. Taking into account the specific localization of the Ag-NOR proteins, our cytochemical and quantitative results, after applying NOR-silver staining in nucleoli of control cells and cells treated with transcription inhibitors, help us to a better understanding of the mechanisms of action of these drugs. Our results support a structural and functional role for the Ag-NOR proteins throughout the course of transcription.