LR_Gapcloser: a tiling path-based gap closer that uses long reads to complete genome assembly

文献类型： 外文期刊

第一作者： Xu, Gui-Cai

作者： Xu, Gui-Cai;Zhu, Rui;Zhang, Yan;Li, Shang-Qi;Wang, Hong-Wei;Li, Jiong-Tang;Xu, Gui-Cai;Zhu, Rui;Zhang, Yan;Li, Shang-Qi;Wang, Hong-Wei;Li, Jiong-Tang;Xu, Gui-Cai;Xu, Tian-Jun;Zhu, Rui

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关键词： gap-closure; genome assembly; third-generation sequencing; next-generation sequencing; repetitive elements

期刊名称：GIGASCIENCE （ 影响因子：6.524； 五年影响因子：8.702 ）

ISSN： 2047-217X

年卷期： 2019 年 8 卷 1 期

页码：

收录情况： SCI

摘要： Background: Completing a genome is an important goal of genome assembly. However, many assemblies, including reference assemblies, are unfinished and have a number of gaps. Long reads obtained from third-generation sequencing (TGS) platforms can help close these gaps and improve assembly contiguity. However, current gap-closure approaches using long reads require extensive runtime and high memory usage. Thus, a fast and memory-efficient approach using long reads is needed to obtain complete genomes. Findings: We developed LR_Gapcloser to rapidly and efficiently close the gaps in genome assembly. This tool utilizes long reads generated from TGS sequencing platforms. Tested on de novo assembled gaps, repeat-derived gaps, and real gaps, LR_Gapcloser closed a higher number of gaps faster and with a lower error rate and a much lower memory usage than two existing, state-of-the art tools. This tool utilized raw reads to fill more gaps than when using error-corrected reads. It is applicable to gaps in the assemblies by different approaches and from large and complex genomes. After performing gap-closure using this tool, the contig N50 size of the human CHM1 genome was improved from 143 kb to 19 Mb, a 132-fold increase. We also closed the gaps in the Triticum urartu genome, a large genome rich in repeats; the contig N50 size was increased by 40%. Further, we evaluated the contiguity and correctness of six hybrid assembly strategies by combining the optimal TGS-based and next-generation sequencing-based assemblers with LR_Gapcloser. A proposed and optimal hybrid strategy generated a new human CHM1 genome assembly with marked contiguity. The contig N50 value was greater than 28 Mb, which is larger than previous non-reference assemblies of the diploid human genome. Conclusions: LR_Gapcloser is a fast and efficient tool that can be used to close gaps and improve the contiguity of genome assemblies. A proposed hybrid assembly including this tool promises reference-grade assemblies. The software is available at http://www.fishbrowser.org/software/LR_Gapcloser/.

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