Abstract

The variability of nucleotide sequences of ribosomal genes and internal transcribed spacers located in the ITS1–5.8S rRNA–ITS2a–2S rRNA–ITS2 region separating the 18S and 28S rRNA genes in the rRNA gene cluster was studied in order to estimate the possibility of using these sequences as molecular markers for species identification and reconstruction of the phylogeny of the family Chironomidae. It was established that, in species of the family Chironomidae, the content of AT base pairs in the sequences of the 5.8S rRNA and 2S rRNA genes is lower (50–57%) than in the sequences of the ITS1, ITS2a, and ITS2 transcribed spacers (64–71%). The sizes of nucleotide sequences of the 5.8S rRNA (123 bp) and 2S rRNA (30 bp) genes in species of the family Chironomidae are conservative, while the sizes of the ITS1, ITS2a, and ITS2 internal transcribed spacers vary both within the species and between species. Neither intraspecific, nor interspecific, nor intergeneric nucleotide differences were found in the sequences of the 2S rRNA gene in 27 species from five genera of the family Chironomidae. Nucleotide sequences of the 5.8S rRNA gene are identical in most studied species of the Chironomus genus. Fixed interspecific nucleotide substitutions were found only in two sites of this gene sequence in three species: C. piger, C. riparius (473С>T), and C. annularius (474A>G). The number of insertions, deletions, and nucleotide substitutions in the sequences of the ITS1, ITS2a, and ITS2 internal transcribed spacers and the whole ITS1–5.8S rRNA–ITS2a–2S rRNA–ITS2 region is generally low within species and increases 5–6 times in sibling species and more than 10 times in morphologically distinct species; that is, it increases in accordance with the growth of taxonomic status of species from the family Chironomidae. The data obtained indicate that nucleotide sequences of ribosomal genes and internal transcribed spacers from the ITS1–5.8S rRNA–ITS2a–2S rRNA–ITS2 region of the rRNA gene cluster can be used as molecular markers for species identification and reconstruction of the phylogeny of the family Chironomidae.

中文翻译：

---

拟蝇科rRNA基因簇ITS1–5.8S rRNA–ITS2a–2S rRNA–ITS2区域中核苷酸序列的变异性

摘要

为了评估使用rRNA基因簇中18S和28S rRNA基因的位置，研究了位于ITS1–5.8S rRNA–ITS2a–2S rRNA–ITS2区中的核糖体基因和内部转录间隔区核苷酸序列的变异性。这些序列作为分子标记，用于鉴定和重建手足科的系统发育。已经确定，在Chironomidae科的物种中，5.8S rRNA和2S rRNA基因的序列中AT碱基对的含量比ITS1，ITS2a和ITS2的序列低（50-57％）转录间隔子（64–71％）。Chironomidae科的5.8S rRNA（123 bp）和2S rRNA（30 bp）基因核苷酸序列的大小是保守的，而ITS1，ITS2a，ITS2和内部转录间隔子在种内和种间都不同。在来自Chironomidae科的5个属的27个物种的2S rRNA基因的序列中，没有发现种内，种间或属间核苷酸差异。5.8S rRNA基因的核苷酸序列在大多数研究物种中是相同的Chironomus属。固定间核苷酸取代唯一发现在该基因序列的两个位点在三个种类：C. piger，C. riparius（473С> T），和C. annularius（474A> G）。ITS1，ITS2a和ITS2内部转录间隔区以及整个ITS1–5.8S rRNA–ITS2a–2S rRNA–ITS2区域的序列中的插入，缺失和核苷酸取代的数量通常在物种内较低，并且增加5–6在同胞物种中的乘数是10倍，在形态上不同的物种中的乘数是10倍以上；也就是说，它随着Chironomidae科的物种的分类学地位的增长而增加。获得的数据表明，rRNA基因簇的ITS1–5.8S rRNA–ITS2a–2S rRNA–ITS2区域的核糖体基因和内部转录间隔区的核苷酸序列可以用作分子标记，用于鉴定和重建该系统的系统发育。家庭猫科。