Abstract：
Many ciliated protists prey on other large microbial organisms, including other protists and microscopic metazoans. The ciliate class Litostomatea unites both predatory and endosymbiotic species. The evolution of predation ability in ciliates remains poorly understood, in part, due to a lack of genomic data. To fill this gap, we acquired the transcriptome profiles of six predatory litostomateans using single-cell sequencing technology and investigated their transcriptomic features. Our results show that: (1) in contrast to non-predatory ciliates, the predatory litostomateans have expanded gene families associated with transmembrane activity and reactive oxidative stress response pathways, potentially as a result of cellular behaviors such as fast contraction and extension; (2) the expansion of the calcium-activated BK potassium channel gene family, which hypothetically regulates cell contractility, is an ancient evolutionary event for the class Litostomatea, suggesting a rewired metabolism associated with the hunting behavior of predatory ciliates; and (3) three whole genome duplication (WGD) events have been detected in litostomateans, with genes associated with biosynthetic processes, transmembrane activity, and calcium-activated potassium channel activity being retained during the WGD events. In addition, we explored the evolutionary relationships among 17 ciliate species, including eight litostomateans, and provided a rich foundational dataset for future in-depth phylogenomic studies of Litostomatea. Our comprehensive analyses suggest that the rewired cellular metabolism via expanded gene families and WGD events might be the potential genetic basis for the predation ability of raptorial ciliates.
摘要：
许多纤毛原生生物捕食其他大型微生物，包括其他原生生物和微观后生动物。纤毛虫类Litostomatea结合了掠食性和内共生物种。纤毛虫捕食能力的演变仍然知之甚少，在某种程度上,由于缺乏基因组数据。为了填补这个空白，我们使用单细胞测序技术获得了6种捕食性litostomeans的转录组谱,并研究了它们的转录组特征.我们的结果表明：（1）与非掠夺性纤毛虫相比，捕食性的利托食性动物已经扩展了与跨膜活性和反应性氧化应激反应途径相关的基因家族，潜在的细胞行为，如快速收缩和延伸的结果;（2）钙激活的BK钾通道基因家族的扩展，假设调节细胞收缩性，是Litostomatea类的古老进化事件，表明与捕食性纤毛虫的狩猎行为相关的重新连接的新陈代谢;和（3）在利托气孔动物中检测到三个全基因组重复（WGD）事件，与生物合成过程相关的基因，跨膜活性，在WGD事件期间保留了钙激活的钾通道活性。此外,我们探索了17种纤毛虫物种之间的进化关系，其中包括8个象牙动物,并为未来对Litostomatea的深入系统基因组研究提供了丰富的基础数据集。我们的综合分析表明，通过扩展的基因家族和WGD事件重新连接的细胞代谢可能是猛禽纤毛虫捕食能力的潜在遗传基础。
