Identification of coiled bodies inBrassica napus nuclei during embryogenesis and early germination

Abstract

Nucleolus-associated bodies characterize interphase nuclei of many plant species. The recent demonstration that such bodies contain small nuclear ribonucleoproteins as well as coilin clearly indicates that they belong to a larger family of nuclear structures, known as coiled bodies, that have been intensively studied in a variety of animal cell types. In a previous work, we have shown that coiled bodies were present in close association with the nucleolus inZea mays dry seeds as well as during subsequent stages of germination. This study reveals that similar nuclear structures were also present duringBrassica napus embryogenesis starting at the torpedo stage and that they were, likewise, generally located on the nucleolar surface. As in the case ofZ. mays, coiled bodies were observed in cells of dry seeds as well as in those of early germinating tissues. These bodies were labelled with monoclonal antibody K121, an antibody reacting with the unique 5′-terminal cap structure containing 2,2,7-trimethylguanosine that characterizes small nuclear RNAs. Owing to their intimate association with the nucleolus in all stages studied, the possibility is considered that, in these plant cells, coiled bodies are assembled on an organizer element located within this organelle.