Krieger Jeannette, Hett Anne Kathrin, Fuerst Paul A, Birstein Vadim J, Ludwig Arne
Department of Ecology and Evolutionary Biology, Brown University, 80 Waterman Street, Providence, RI 02912, USA.
J Hered. 2006 May-Jun;97(3):218-25. doi: 10.1093/jhered/esj035. Epub 2006 May 19.
Significant intraindividual variation in the sequence of the 18S rRNA gene is unusual in animal genomes. In a previous study, multiple 18S rRNA gene sequences were observed within individuals of eight species of sturgeon from North America but not in the North American paddlefish, Polyodon spathula, in two species of Polypterus (Polypterus delhezi and Polypterus senegalus), in other primitive fishes (Erpetoichthys calabaricus, Lepisosteus osseus, Amia calva) or in a lungfish (Protopterus sp.). These observations led to the hypothesis that this unusual genetic characteristic arose within the Acipenseriformes after the presumed divergence of the sturgeon and paddlefish families. In the present study, a survey of nearly all Eurasian acipenseriform species was conducted to examine 18S rDNA variation. Intraindividual variation was not found in the polyodontid species, the Chinese paddlefish, Psephurus gladius, but variation was detected in all Eurasian acipenserid species. The comparison of sequences from two major segments of the 18S rRNA gene and identification of sites where insertion/deletion events have occurred are placed in the context of evolutionary relationships within the Acipenseriformes and the evolution of rDNA variation in this group.
18S rRNA基因序列在个体内存在显著差异，这在动物基因组中并不常见。在之前的一项研究中，在来自北美的8种鲟鱼个体中观察到多个18S rRNA基因序列，但在北美匙吻鲟、多鳍鱼属的两个物种（德氏多鳍鱼和塞内加尔多鳍鱼）、其他原始鱼类（喀麦隆沼鳝、骨舌鱼、雀鳝）或一种肺鱼（原鳍鱼属）中未观察到。这些观察结果导致了这样一种假设，即这种不寻常的遗传特征是在鲟形目内部，在假定的鲟鱼和匙吻鲟科分化之后出现的。在本研究中，对几乎所有欧亚鲟形目物种进行了调查，以检查18S rDNA的变异情况。在匙吻鲟科物种中华匙吻鲟中未发现个体内变异，但在所有欧亚鲟科物种中均检测到变异。将18S rRNA基因两个主要片段的序列比较以及插入/缺失事件发生位点的鉴定置于鲟形目内部的进化关系以及该类群rDNA变异进化的背景下。
