Dynamics of structural and functional association of nucleolar chromosomes in cells of the hexaploid wheat Triticum aestivum L. at different stages of the cell cycle and during genome polyploidization.
Quantitative analysis of interphase association of the nucleolar chromosomes at different stages of the cell cycle and during genome polyploidization was carried out. Cells of various tissues of hexaploid wheat Triticum aestivum L. (Moskovskaya-35) were used, including diploid root meristematic cells, endopolyploid root cells, triploid endosperm cells and antipodal cells with polytene chromosomes. Interphase nucleoli impregnated with silver or stained with autoimmune antibodies to 53 kDa nucleolar protein served as markers of the nucleolar chromosome association. The following data were obtained: (1) silver-staining revealed two pairs of homologous chromosomes 1B and 6B with active nucleolus-organizing regions in the root meristematic cells; (2) maximal number of nucleoli in diploid meristematic cells reaches four, which corresponds to the number of chromosomes with active organizers; (3) analysis of cells at different stages of the cell cycle has shown that the tendency to the nucleoli association is observed as soon as cells pass individual stages of the cycle; (4) after DNA and chromosome reduplication, the nucleolus-organizing regions in sister chromatids function as a common structure-functional complex; (5) in endopolyploid root cells and antipodal cells with polytene chromosomes, the number of nucleoli does not correlate with ploidy level, and an additional nucleolus revealed in some cells is the result of activation of the latent organizer in one of the nucleolar chromosomes; (6) in the triploid endosperm nucleologenesis, the stage of prenucleolar bodies is missing. Our data suggest that "fusion" of nucleoli and reduction of their number due to the "satellite" association of the nucleolar chromosomes are two independent processes regulated by different mechanisms.
Khoudoleeva
O A
OA
Belozersky Institute of Physico-Chemical Biology, Moscow, Russia. olga_kh@yahoo.com
Lazareva
E M
EM
Kononenko
N V
NV
Chentsov
Y S
YS
Polyakov
V Y
VY
D002453:Cell Cycle; D002466:Cell Nucleolus; D002467:Cell Nucleus; D004171:Diploidy; D018745:Genome, Plant; D018519:Meristem; D008938:Mitosis / Q000502:physiology; D018517:Plant Roots; D011123:Polyploidy; D014908:Triticum / Q000235:genetics*