Microorganisms have expanded our understanding of biodiversity and exhibit crucial research values. Ciliated protists are a highly differentiated group of eukaryotic microorganisms with exceptional features, such as numerous cilia, dimorphic nuclei, and genome-wide gene rearrangement, that have made them ideal research models for revealing many biological processes. Studies of the ciliate Tetrahymena thermophila have greatly advanced our understanding of RNA self-splicing and enzymatic activity, telomere biology, and the Nobel Prize-winning telomerase mechanisms. Genome rearrangement during the sexual reproduction (conjugation) of ciliates, involving the elimination of ~25–90% of germline DNA, provides an opportunity to study large-scale genome remodelling while also revealing a more thorough mode of transposon repression, i.e. Piwi-interacting small RNA-mediated DNA deletion in the somatic nucleus. Although much progress has been made, research has focused mainly on a few model species that are amenable to gene editing. For other species, although they are more suitable to address some scientific gaps, research cannot be carried out owing to limitations of genetic engineering. Here, we summarize the existing genetic engineering strategies for ciliates, expecting to provide inspiration for the development and optimization of genetic engineering tools for ciliates and other organisms cannot yet be edited genetically.

中文翻译：

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纤毛虫研究中基因操作工具的概述，重点是基因敲除、敲低和过度表达

微生物拓展了我们对生物多样性的理解，并展现出重要的研究价值。纤毛原生生物是一类高度分化的真核微生物，具有众多的纤毛、二态性核和全基因组基因重排等特殊特征，这使得它们成为揭示许多生物过程的理想研究模型。对纤毛虫嗜热四膜虫的研究极大地增进了我们对 RNA 自剪接和酶活性、端粒生物学以及获得诺贝尔奖的端粒酶机制的理解。纤毛虫有性繁殖（接合）过程中的基因组重排涉及约 25-90% 种系 DNA 的消除，为研究大规模基因组重塑提供了机会，同时也揭示了更彻底的转座子抑制模式，即 Piwi 相互作用体细胞核中小RNA介导的DNA缺失。尽管已经取得了很大进展，但研究主要集中在一些适合基因编辑的模型物种上。对于其他物种来说，虽然它们更适合解决一些科学空白，但由于基因工程的限制而无法进行研究。在此，我们总结了现有的纤毛虫基因工程策略，期望为纤毛虫和其他尚不能进行基因编辑的生物的基因工程工具的开发和优化提供启发。