Localization of fibrillarin, 53 kDa protein and Ag-NOR proteins in the nuclei of giant antipodal cells of the wheat Triticum aestivum

Distribution of nucleolar argentophylic proteins, fibrillarin and 53 kDa protein, in highly polyploid nuclei of antipodal cells of Triticum aestivum L. was studied at different stages of the embryo sac development. The main results are as follows. 1. Ag-NOR proteins and fibrillarin form clusters are distributed in the giant nucleoli, whereas 53 kDa protein is mainly localized on the nucleolar periphery. Ag-NOR proteins and fibrillarin are accumulated as globular nucleolar-like particles--micronucleoli. 2. Dynamics of Ag-NOR proteins, fibrillarin and 53 kDa protein depends on the proliferative activity of endosperm cells. In embryo sacs with non-dividing endosperm cells at interphase stages, Ag-NOR proteins and fibrillarin were observed only within nucleoli and micronucleoli. In embryo sacs with dividing endosperm cells, fibrillarin and 53 kDa protein formed heterogeneous globular bodies varying in size. Simultaneously, some argentophylic material was observed in giant chromosomes. This may be due, presumably, to a partial or complete disappearance of the nucleoli of antipods and transition of some nucleolar components into the peripheral material of giant polytene chromosomes. We suggest that giant nuclei of antipodal cells may undergo cyclic transformation similar to those in the nuclei of dividing cells.