Universidad de la República, Facultad de Ciencias, Sección Genética Evolutiva, Montevideo, Uruguay.
Mem Inst Oswaldo Cruz. 2013 May;108(3):376-82. doi: 10.1590/S0074-02762013000300017.
In this study, we used fluorescence in situ hybridisation to determine the chromosomal location of 45S rDNA clusters in 10 species of the tribe Rhodniini (Hemiptera: Reduviidae: Triatominae). The results showed striking inter and intraspecific variability, with the location of the rDNA clusters restricted to sex chromosomes with two patterns: either on one (X chromosome) or both sex chromosomes (X and Y chromosomes). This variation occurs within a genus that has an unchanging diploid chromosome number (2n = 22, including 20 autosomes and 2 sex chromosomes) and a similar chromosome size and genomic DNA content, reflecting a genome dynamic not revealed by these chromosome traits. The rDNA variation in closely related species and the intraspecific polymorphism in Rhodnius ecuadoriensis suggested that the chromosomal position of rDNA clusters might be a useful marker to identify recently diverged species or populations. We discuss the ancestral position of ribosomal genes in the tribe Rhodniini and the possible mechanisms involved in the variation of the rDNA clusters, including the loss of rDNA loci on the Y chromosome, transposition and ectopic pairing. The last two processes involve chromosomal exchanges between both sex chromosomes, in contrast to the widely accepted idea that the achiasmatic sex chromosomes of Heteroptera do not interchange sequences.
在这项研究中，我们使用荧光原位杂交技术来确定 Rhodniini 族（半翅目：红蝽科：三锥虫科）10 个物种的 45S rDNA 簇的染色体位置。结果显示出明显的种间和种内变异性，rDNA 簇的位置仅限于性染色体，有两种模式：要么在一个（X 染色体）上，要么在两个性染色体（X 和 Y 染色体）上。这种变异发生在一个具有不变的二倍体染色体数（2n=22，包括 20 条常染色体和 2 条性染色体）和相似的染色体大小和基因组 DNA 含量的属内，反映了基因组的动态，而这些染色体特征并没有揭示出来。在密切相关的物种中 rDNA 的变异和 Rhodnius ecuadoriensis 的种内多态性表明，rDNA 簇的染色体位置可能是识别最近分化的物种或种群的有用标记。我们讨论了核糖体基因在 Rhodniini 族中的祖先位置以及 rDNA 簇变异涉及的可能机制，包括 Y 染色体上 rDNA 基因座的丢失、转位和异位配对。后两个过程涉及两个性染色体之间的染色体交换，与普遍认为的半翅目非联会性性染色体不交换序列的观点相反。
