纤毛虫两型核之间的基因组重组

Genome rearrangements between the dimorphic nuclei in ciliates

纤毛虫原生动物是一大类结构高度特化、多样性极高的单细胞真核生物。该类群的主要特征是具有高度分化的细胞器、分司不同功能(负责生殖的小核和营养的大核)的两型细胞核以及特有的接合生殖方式。纤毛虫独特的两型核结构为有性生殖过程中全基因组范围的DNA重组提供了可能:包括染色体的断裂、序列的删除、基因组的重排、染色体多倍化等。新近的研究显示,这一过程由RNA介导的表观遗传学控制。现就纤毛虫的基因组重组过程及其RNA相关的分子机理进行概述,并简要介绍作为其基础的大小核结构特点和有性生殖行为。

Ciliated protozoans （ciliates） are the most morphologically complex, highly differentiated and widespread taxon among unicellular eukaryotic organisms. Ciliates are characterized by their complicated organelles and cytoskeleton structures, special nuclear dimorphism, and unique sexual reproduction （conjugation）. The dual genomes （germline micronucleus and somatic macronucleus） provide possibilities for genome-wide DNA rearrangements during the development of the macronuclear genome in the process of sexual reproduction, including fragmentation, elimination of internal excised sequences, genome unscrambling, amplification, etc. Recent researches reveal that these processes are manipulated by RNA-mediated epigenetics. In this paper, we introduce the structural features of the dual genomes and the process of sexual reproduction, with emphases on reviewing the process of genome rearrangements as well as RNA-related molecular mechanism, which will contribute to understanding the dynamic nature of eukaryotic genomes.