Identification and Characterization of Base-Substitution Mutations in the Macronuclear Genome of the Ciliate Tetrahymena thermophila.
Identification and Characterization of Base-Substitution Mutations in the Macronuclear Genome of the Ciliate Tetrahymena thermophila.
复制标题
嗜热纤毛虫大核基因组碱基取代突变的鉴定和表征
DOI：
10.1093/gbe/evaa232
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发表时间：
2021-01-07
影响因子：
3.3
通讯作者：
Miao W
中科院分区：
文献类型：
--
作者：
Wang G;Fu L;Xiong J;Mochizuki K;Fu Y;Miao W
多倍体可提供适应性优势并推动进化。纤毛虫中多倍体大核（MAC）的无丝分裂作为一种非有性遗传机制，可增强对胁迫条件的适应能力，从而为研究多倍体的进化作用提供了一个独特的模型。突变是导致进化和适应的变异的主要来源；然而，到目前为止，在这些过程中纤毛虫MAC基因组中发生的从头突变尚未得到表征，其生物学影响也未确定。在此，我们进行了长期进化实验，以直接探究模式纤毛虫嗜热四膜虫中的从头MAC突变及其分子特征。我们建立了一种简单而有效的方法来检测进化群体中的碱基替换突变，同时过滤掉由重复序列和程序性基因组重排导致的大多数假阳性碱基替换。利用MassARRAY系统对检测到的突变进行了严格验证。经过验证的突变显示出强烈的G/C→A/T偏向，这与在其他物种中的观察结果一致。此外，进化群体生长速率的逐步提高表明，其中一些突变可能与细胞适应性有关。所建立的突变鉴定和验证方法将是一种极有价值的资源，使纤毛虫成为研究多倍体在进化中作用的重要模型系统。
Abstract Polyploidy can provide adaptive advantages and drive evolution. Amitotic division of the polyploid macronucleus (MAC) in ciliates acts as a nonsexual genetic mechanism to enhance adaptation to stress conditions and thus provides a unique model to investigate the evolutionary role of polyploidy. Mutation is the primary source of the variation responsible for evolution and adaptation; however, to date, de novo mutations that occur in ciliate MAC genomes during these processes have not been characterized and their biological impacts are undefined. Here, we carried out long-term evolution experiments to directly explore de novo MAC mutations and their molecular features in the model ciliate, Tetrahymena thermophila. A simple but effective method was established to detect base-substitution mutations in evolving populations whereas filtering out most of the false positive base-substitutions caused by repetitive sequences and the programmed genome rearrangements. The detected mutations were rigorously validated using the MassARRAY system. Validated mutations showed a strong G/C→A/T bias, consistent with observations in other species. Moreover, a progressive increase in growth rate of the evolving populations suggested that some of these mutations might be responsible for cell fitness. The established mutation identification and validation methods will be an invaluable resource to make ciliates an important model system to study the role of polyploidy in evolution.