ABSTRACT
The DNA intercalator 9-aminoachridine was used for obtaining high-resolution DAPI patterns of chromosomes of Pisum sativum L. with more than 300 bands per haploid chromosome set. The karyotypes of three pea varieties, Viola, Capital, and Rosa Crown, and two translocation lines, L-108 (T(2-4s)) and M-10 (T(2-7s)), were examined. Based on the results of DAPI staining, we have identified chromosomes, constructed idiograms, and established breakpoints of chromosome translocations. Lines L-108 (T(2-4s)) and M-10 (T(2-7s)) were shown to appear as a result of respectively one translocation between chromosomes 2 and 4 and two translocations between chromosomes 2 and 7. All varieties and translocation lines of pea were examined using fluorescence in situ hybridization (FISH) with telomere repetition probes, 5S and 45S wheat DNA probes. Transcriptional activity of 45S rRNA was detected by Ag-NOR staining. Telomere repetitions were shown to be located only in telomeric chromosome regions. Using high-resolution DAPI staining allowed us to verify localization of 5S genes on pea chromosomes 1, 3, and 5. 45S rDNAs were localized in the secondary constriction regions on the satellite and the satellite thread of chromosome and on the satellite thread and in more proximal satellite heterochromatic region of chromosome 7. The size of 45S rDNA signal on chromosome 7 was larger and its transcriptional activity, higher than the corresponding parameters on chromosome 4 in most of the forms studied. A visual comparison of the results of FISH and Ag-NOR staining of normal and translocated pea chromosomes did not reveal any significant differences between them. The translocations of the satellite chromosomes apparently did not cause significant changes either in the amount of the ribosomal genes or in their transcriptional activity.
