Genome. 1996 Dec;39(6):1150-8. doi: 10.1139/g96-145.
The distribution of the 5S and 18S-5.8S-26S (18S-26S) ribosomal RNA (rRNA) gene families on chromosomes of all diploid Aegilops species was studied by in situ hybridization with pTa71 (18S-26S rDNA) and pTa794 (5S rDNA) DNA clones. One major 18S-26S rDNA locus was found in the nucleolus organizer region (NOR) of each of the species Aegilops tauschii and Aegilops uniaristata and two loci were detected in the remaining species. In addition to major NORs, from one to nine minor loci were observed; their numbers and chromosomal locations were species-specific. Some minor loci were polymorphic, whereas others were conserved. One or two 5S rDNA loci were observed in the short arms of the chromosomes of groups 1 and 5 of all diploid Aegilops species except Ae. uniaristata, where one 5S rDNA site was located in the distal part of the long arm of chromosome 1N. The 5S rDNA loci were not associated with NORs; however, the relative positions of two ribosomal RNA gene families were diagnostic for chromosomes of homoeologous groups 1, 5, and 6. Implications of these results for establishing phylogenetic relationships of diploid Aegilops species and mechanisms of genome differentiation are discussed. Key words : wheat, Triticum, Aegilops, 5S rRNA, 18S-26S rRNA, in situ hybridization, evolution.
通过用 pTa71（18S-26S rDNA）和 pTa794（5S rDNA）DNA 克隆进行原位杂交，研究了所有二倍体节节麦物种染色体上的 5S 和 18S-5.8S-26S（18S-26S）核糖体 RNA（rRNA）基因家族的分布。在物种节节麦和 Aegilops uniaristata 的核仁组织区（NOR）中发现了一个主要的 18S-26S rDNA 基因座，而在其余物种中则检测到了两个基因座。除了主要的 NOR 之外，还观察到了一个到九个次要的基因座；它们的数量和染色体位置是物种特异性的。一些次要基因座是多态的，而另一些则是保守的。除了 Ae. uniaristata 之外，所有二倍体节节麦物种的 1 组和 5 组染色体的短臂中都观察到一个或两个 5S rDNA 基因座，其中一个 5S rDNA 位点位于 1N 染色体的长臂远端。5S rDNA 基因座与 NOR 无关；然而，两个核糖体 RNA 基因家族的相对位置对于同源群 1、5 和 6 的染色体是具有诊断意义的。这些结果对于建立二倍体节节麦物种的系统发育关系和基因组分化的机制具有重要意义。关键词：小麦、Triticum、节节麦、5S rRNA、18S-26S rRNA、原位杂交、进化。
