de novo assembly and population genomic survey of natural yeast isolates with the Oxford Nanopore MinION sequencer

Abstract

Oxford Nanopore Technologies Ltd (Oxford, UK) have recently commercialized MinION, a small and low-cost single-molecule nanopore sequencer, that offers the possibility of sequencing long DNA fragments. The Oxford Nanopore technology is truly disruptive and can sequence small genomes in a matter of seconds. It has the potential to revolutionize genomic applications due to its portability, low-cost, and ease of use compared with existing long reads sequencing technologies. The MinION sequencer enables the rapid sequencing of small eukaryotic genomes, such as the yeast genome. Combined with existing assembler algorithms, near complete genome assemblies can be generated and comprehensive population genomic analyses can be performed. Here, we resequenced the genome of the Saccharomyces cerevisiae S288C strain to evaluate the performance of nanopore-only assemblers. Then we de novo sequenced and assembled the genomes of 21 isolates representative of the S. cerevisiae genetic diversity using the MinION platform. The contiguity of our assemblies was 14 times higher than the Illumina-only assemblies and we obtained one or two long contigs for 65% of the chromosomes. This high continuity allowed us to accurately detect large structural variations across the 21 studied genomes. Moreover, because of the high completeness of the nanopore assemblies, we were able to produce a complete cartography of transposable elements insertions and inspect structural variants that are generally missed using a short-read sequencing strategy.