三种四膜虫全基因组N6-甲基腺嘌呤比较研究

为了揭示N6-甲基腺嘌呤(6mA)在近缘物种间的分布规律和物种进化过程中的变化, 研究在分离2种四膜虫(Tetrahymena malaccensis和Tetrahymena pyriformi)大核的基础上, 利用三代测序技术绘制了其全基因组单碱基分辨率6mA图谱, 结合公共数据库中已有的模式种Tetrahymena thermophila数据, 开展了3种四膜虫比较6mA甲基化组分析, 发现: (1)3种四膜虫6mA甲基化位点分布特征类似, 包括呈约200 bp周期性分布和具有保守AT基序; (2)6mA主要分布于基因的5′端, 在种间直系同源基因上的分布模式具有区域近似性, 但在单碱基水平不完全保守; (3)在种内近期复制的并系同源基因中, 6mA分布在单碱基水平具有较高的保守性; (4)结合3种四膜虫的分化时间, 估算出了四膜虫中6mA动态变化过程, 6mA位点建立的速度大约为每Mb每百万年69.9—226个位点。

COMPARATIVE 6MA METHYLOME IN THREE TETRAHYMENA SPECIES

N6-methyladenine (6mA) is a type of DNA methylation epigenetic modification. In recent years, the development of third generation sequencing technology has led to many important advances in 6mA research at the whole genome level. However, a few of comparative m6A methylome studies have been performed in close related species. In order to reveal the distribution of 6mA and the changes in close related species, we isolated and sequenced the macronuclei genome of Tetrahymena malaccensis and Tetrahymena pyriformis using PacBio SMRT sequencing techonology. Combining with the previous published Tetrahymena thermophila sequencing data, comparative 6mA methylome analysis in the three species of Tetrahymena was carried out, and we found that: (1) The 6mA methylation site distribution characteristics in the three species of Tetrahymena were similar, including periodic distribution about 200 bp and conservative AT motif; (2) 6mA was mainly distributed at the 5' of the gene body, and the 6mA distributed in approximate regions in gene body among orthologs, but showed low conservation at the single nucleotide level; (3) In recent duplicated inparalogs, the 6mA distribution showed high single nucleotide level conservation; (4) According to the divergence time of the three species of Tetrahymena, the speed of new 6mA sites establishment was about 69.9—226 sites per Mb sequences per million years.