Fontana Francesco, Lanfredi Massimo, Congiu Leonardo, Leis Marilena, Chicca Milvia, Rossi Remigio
Department of Biology, University of Ferrara, via L. Borsari, 46 I-44100 Ferrara, Italy.
Genome. 2003 Jun;46(3):473-7. doi: 10.1139/g03-007.
The number and distribution of the 18S-28S and 5S rRNA (rDNA) gene sequences were examined on mitotic chromosomes of six sturgeon species by two-colour in situ hybridization. Four of the six species, Huso huso, Acipenser stellatus, Acipenser sturio, and Acipenser ruthenus, with about 120 chromosomes, showed from six to eight 18S-28S rDNA signals, while 5S rDNA signals were on only one chromosome pair. The two species with 250-270 chromosomes, Acipenser baerii and Acipenser transmontanus, showed from 10 to 12 18S-28S sites and two chromosome pairs bearing 5S rDNA signals. In all examined species, the rather intense 5S rDNA signals apparently overlapped those of 18S-28S rDNA. These data support the diploid-tetraploid relationships between the two chromosome groups of sturgeons. The close association between the two rDNA families in species belonging to an ancestral fish order, such as Acipenseriformes, supports the hypothesis that the association represents a primitive condition.
通过双色原位杂交技术，对六种鲟鱼有丝分裂染色体上18S - 28S和5S rRNA（rDNA）基因序列的数量和分布进行了检测。六种鲟鱼中的四种，即欧洲鳇（Huso huso）、 stellatus鲟（Acipenser stellatus）、大西洋鲟（Acipenser sturio）和俄罗斯鲟（Acipenser ruthenus），约有120条染色体，显示出6至8个18S - 28S rDNA信号，而5S rDNA信号仅位于一对染色体上。另外两种有250 - 270条染色体的鲟鱼，即贝氏鲟（Acipenser baerii）和高首鲟（Acipenser transmontanus），显示出10至12个18S - 28S位点以及两对带有5S rDNA信号的染色体。在所有检测的物种中，相当强烈的5S rDNA信号显然与18S - 28S rDNA信号重叠。这些数据支持了鲟鱼两个染色体组之间的二倍体 - 四倍体关系。在属于古老鱼类目（如鲟形目）的物种中，两个rDNA家族之间的紧密关联支持了这样一种假设，即这种关联代表了一种原始状态。
