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Vztahy mezi úrovní ploidie, velikostí genomu a velikostí buňky v sérii modelů ryb ploidní úrovně od 2n do 14n
BYTYUTSKYY, Dmytro
The ploidy level of diploid and induced triploid tench, Tinca tinca, was verified using flow cytometry to determine relative DNA content of 4',6-diamidino-2-phenylindole (DAPI)-stained erythrocyte nuclei. The C-value (haploid nuclear DNA content; pgDNA.nucleus-1) of these same individuals was determined by means of Feulgen image analysis densitometry, in comparison to the chicken standard (Gallus gallus domesticus; 1.25 pgDNA.nucleus-1, P < 0.05), using three different approaches. Highly similar mean C-values were obtained, thus confirming the possibility of using tench blood as standard in European pond aquaculture for ploidy and DNA content determination in fishes. Feulgen image analysis densitometry (FIAD), flow cytometry (FC) and confocal laser scanning microscopy (CLSM) were used to study the relationship between the DNA content (pgDNA.nucleus-1), nuclear area (?m2), nuclear volume (?m3) and 3-D structure of erythrocyte nuclei in a series of fish ploidy level models: diploid tench (Tinca tinca) (2n), Cuban gar (Atractosteus tristoechus) (2n), triploid tench (3n), evolutionary tetraploid sterlet (Acipenser ruthenus) and stellate sturgeons (A. stellatus) (4n), evolutionary octaploid Siberian sturgeon (A. baerii) and Russian sturgeon (A. gueldenstaedtii) (8n), spontaneous triploid Siberian and Russian sturgeons exhibiting dodecaploidy (12n), evolutionary 12n shortnose sturgeon (A. brevirostrum), and experimentally obtained sturgeon hybrids that were tetraploid, hexaploid (6n), heptaploid (7n), octaploid (8n), decaploid (10n), dodecaploid (12n) and/or tetradecaploid (14n). Standards used for FIA were blood smears of chicken (2.5 pgDNA.nucleus-1), diploid and induced triploid tench (2.04 and 3.1 pgDNA.nucleus-1, respectively). All ploidy levels were first verified by means of FC. Increase in ploidy was accompanied by growth of the nucleus and an increase in the number of flattened ellipsoid nuclei with increased transverse diameter. The volume (Vvoxel) of erythrocyte nuclei, as the sum of voxels calculated from live cells, seems more accurate than volume (Vaxis) calculated from measuring the major and minor axis, especially at higher and odd ploidy levels. Data of absolute and relative DNA content were in agreement with previously published reports. Species of the same ploidy level, however differing in their DNA content, exhibited a similar mean erythrocyte nuclear area, as could be demonstrated on A. ruthenusand and A. stellatus (19.27 and 19.79 ?m2 with a respective mean DNA content of 3.72 and 4.68 pgDNA.nucleus-1) and volume as could be demonstrated on a A. ruthenus and hybrid of A. ruthenus and H. huso(48.3 and 48.9 ?m3 with a respective mean DNA content of 3.74 and 3.10 pg DNA.nucleus-1). Similar relationship was found for the ploidy 6n, 8n, 10n, 12n. The 0.46-1.58 pgDNA increments in DNA content of erythrocytes thus had no effect on their nuclear area/volume. With increasing ploidy level, the DNA concent ration (pgDNA per 1 ?m3 of erythrocyte nuclear volume) as well as surface-to-volume ratio was found not to increase linearly. Nuclear DNA content appeared to be more condensed with an increase of the ploidy level. Observed results deduce properties of whole cell and particularly of the nuclei in series of ploidy levels fishes, adding conformations of nucleotypic hypothesis in context of cell/nuclear size and genome size relationships, as well as taxonomic position of sturgeons.
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