The nematode Pristionchus pacificus is an established model for integrative evolutionary biology and comparative studies with Caenorhabditis elegans. While an existing genome draft facilitated the identification of several genes controlling various developmental processes, its high degree of fragmentation complicated virtually all genomic analyses. Here, we present a de novo genome assembly from single-molecule, long-read sequencing data consisting of 135 P. pacificus contigs. When combined with a genetic linkage map, 99% of the assembly could be ordered and oriented into six chromosomes. This allowed us to robustly characterize chromosomal patterns of gene density, repeat content, nucleotide diversity, linkage disequilibrium, and macrosynteny in…
Ammopiptanthus nanus is a rare broad-leaved shrub that is found in the desert and arid regions of Central Asia. This plant species exhibits extremely high tolerance to drought and freezing and has been used in abiotic tolerance research in plants. As a relic of the tertiary period, A. nanus is of great significance to plant biogeographic research in the ancient Mediterranean region. Here, we report a draft genome assembly using the Pacific Biosciences (PacBio) platform and gene annotation for A. nanus.A total of 64.72 Gb of raw PacBio sequel reads were generated from four 20-kb libraries. After filtering, 64.53 Gb…
Complex allelic variation hampers the assembly of haplotype-resolved sequences from diploid genomes. We developed trio binning, an approach that simplifies haplotype assembly by resolving allelic variation before assembly. In contrast with prior approaches, the effectiveness of our method improved with increasing heterozygosity. Trio binning uses short reads from two parental genomes to first partition long reads from an offspring into haplotype-specific sets. Each haplotype is then assembled independently, resulting in a complete diploid reconstruction. We used trio binning to recover both haplotypes of a diploid human genome and identified complex structural variants missed by alternative approaches. We sequenced an F1…
Third-generation long-range DNA sequencing and mapping technologies are creating a renaissance in high-quality genome sequencing. Unlike second-generation sequencing, which produces short reads a few hundred base-pairs long, third-generation single-molecule technologies generate over 10,000 bp reads or map over 100,000 bp molecules. We analyze how increased read lengths can be used to address long-standing problems in de novo genome assembly, structural variation analysis and haplotype phasing.
Microsatellites, or simple sequence repeats (SSRs), have long played a major role in genetic studies due to their typically high polymorphism. They have diverse applications, including genome mapping, forensics, ascertaining parentage, population and conservation genetics, identification of the parentage of polyploids, and phylogeography. We compare SSRs and newer methods, such as genotyping by sequencing (GBS) and restriction site associated DNA sequencing (RAD-Seq), and offer recommendations for researchers considering which genetic markers to use. We also review the variety of techniques currently used for identifying microsatellite loci and developing primers, with a particular focus on those that make use of next-generation…
Completion of eukaryal genomes can be difficult task with the highly repetitive sequences along the chromosomes and short read lengths of second-generation sequencing. Saccharomyces cerevisiae strain CEN.PK113-7D, widely used as a model organism and a cell factory, was selected for this study to demonstrate the superior capability of very long sequence reads for de novo genome assembly. We generated long reads using two common third-generation sequencing technologies (Oxford Nanopore Technology (ONT) and Pacific Biosciences (PacBio)) and used short reads obtained using Illumina sequencing for error correction. Assembly of the reads derived from all three technologies resulted in complete sequences for…