Wu Zuo-Wei, Wang Qi-Ming, Liu Xin-Zhan, Bai Feng-Yan
State key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
Mycology. 2016 Jul 11;7(3):102-111. doi: 10.1080/21501203.2016.1204369. eCollection 2016.
A concerted evolution model has been proposed to explain the observed lack of sequence variation among the multiple ribosomal RNA (rRNA) gene copies in many different eukaryotic species. Recent studies on the level of intragenomic variations in the rRNA gene repeats of fungi resulted in controversial conclusions. In this study, we clearly showed that significant polymorphisms of the internal transcribed spacers (ITS1 and ITS2) of ribosomal DNA (rDNA) exist within the genome of a strain of the yeast species . More interestingly, we showed that the intragenomic ITS sequence polymorphisms were formed by intergenomic rDNA recombination among different strains with significantly different ITS sequences. Intergenomic rDNA recombination was also responsible for the diversification of rDNA sequences in different strains of the species. After the events bring together different rDNA types in individual genomes of the strains compared, rDNA sequence heterogeneity has remained in the genome of one but eliminated by homogenisation in the genomes of other strains. Our findings show new clue for further investigation on the mechanism of concerted evolution of rRNA genes in eukaryotes.
一种协同进化模型已被提出，以解释在许多不同真核生物物种中多个核糖体RNA（rRNA）基因拷贝间观察到的序列变异缺失现象。近期关于真菌rRNA基因重复序列的基因组内变异水平的研究得出了有争议的结论。在本研究中，我们明确表明，酵母菌种的一个菌株基因组内存在核糖体DNA（rDNA）的内部转录间隔区（ITS1和ITS2）的显著多态性。更有趣的是，我们表明基因组内ITS序列多态性是由具有显著不同ITS序列的不同菌株间的基因组间rDNA重组形成的。基因组间rDNA重组也导致了该物种不同菌株中rDNA序列的多样化。在将不同rDNA类型汇集到所比较菌株的个体基因组中的事件发生后，rDNA序列异质性在一个菌株的基因组中保留了下来，但在其他菌株的基因组中通过同质化作用而消除。我们的发现为进一步研究真核生物中rRNA基因协同进化的机制提供了新线索。
