Triplophysa is an endemic fish genus of the Tibetan Plateau in China. Triplophysa tibetana, which lives at a recorded altitude of ~4,000 m and plays an important role in the highland aquatic ecosystem, serves as an excellent model for investigating high-altitude environmental adaptation. However, evolutionary and conservation studies of T. tibetana have been limited by scarce genomic resources for the genus Triplophysa. In the present study, we applied PacBio sequencing and the Hi-C technique to assemble the T. tibetana genome. A 652-Mb genome with 1,325 contigs with an N50 length of 3.1 Mb was obtained. The 1,137 contigs were further assembled into 25 chromosomes,…
Caenorhabditis elegans was the first multicellular eukaryotic genome sequenced to apparent completion. Although this assembly employed a standard C. elegans strain (N2), it used sequence data from several laboratories, with DNA propagated in bacteria and yeast. Thus, the N2 assembly has many differences from any C. elegans available today. To provide a more accurate C. elegans genome, we performed long-read assembly of VC2010, a modern strain derived from N2. Our VC2010 assembly has 99.98% identity to N2 but with an additional 1.8 Mb including tandem repeat expansions and genome duplications. For 116 structural discrepancies between N2 and VC2010, 97 structures…
Long-read sequencing, CENP-A ChIP, and chromatin fiber imaging reveal the composition and organization of Drosophila melanogaster centromeres, which have long remained elusive despite the high quality of this species’ genome. assembly.
We present a high-quality de novo genome assembly (rheMacS) of the Chinese rhesus macaque (Macaca mulatta) using long-read sequencing and multiplatform scaffolding approaches. Compared to the current Indian rhesus macaque reference genome (rheMac8), rheMacS increases sequence contiguity 75-fold, closing 21,940 of the remaining assembly gaps (60.8 Mbp). We improve gene annotation by generating more than two million full-length transcripts from ten different tissues by long-read RNA sequencing. We sequence resolve 53,916 structural variants (96% novel) and identify 17,000 ape-specific structural variants (ASSVs) based on comparison to ape genomes. Many ASSVs map within ChIP-seq predicted enhancer regions where apes and macaque…
Despite the conserved essential function of centromeres, centromeric DNA itself is not conserved. The histone-H3 variant, CENP-A, is the epigenetic mark that specifies centromere identity. Paradoxically, CENP-A normally assembles on particular sequences at specific genomic locations. To gain insight into the specification of complex centromeres, here we take an evolutionary approach, fully assembling genomes and centromeres of related fission yeasts. Centromere domain organization, but not sequence, is conserved between Schizosaccharomyces pombe, S. octosporus and S. cryophilus with a central CENP-ACnp1 domain flanked by heterochromatic outer-repeat regions. Conserved syntenic clusters of tRNA genes and 5S rRNA genes occur across the centromeres…
Mithun (Bos frontalis), also called gayal, is an endangered bovine species, under the tribe bovini with 2n?=?58 XX chromosome complements and reared under the tropical rain forests region of India, China, Myanmar, Bhutan and Bangladesh. However, the origin of this species is still disputed and information on its genomic architecture is scanty so far. We trust that availability of its whole genome sequence data and assembly will greatly solve this problem and help to generate many information including phylogenetic status of mithun. Recently, the first genome assembly of gayal, mithun of Chinese origin, was published. However, an improved reference genome…
The ability to generate long sequencing reads and access long-range linkage information is revolutionizing the quality and completeness of genome assemblies. Here we use a hybrid approach that combines data from four genome sequencing and mapping technologies to generate a new genome assembly of the honeybee Apis mellifera. We first generated contigs based on PacBio sequencing libraries, which were then merged with linked-read 10x Chromium data followed by scaffolding using a BioNano optical genome map and a Hi-C chromatin interaction map, complemented by a genetic linkage map.Each of the assembly steps reduced the number of gaps and incorporated a substantial…
Intergeneric hybridization between industrial chicory (Cichorium intybus L.) and Cicerbita alpina Walbr. induces interspecific hybrids and haploid chicory plants after in vitro embryo rescue. The protocol yielded haploids in 5 out of 12 cultivars pollinated; altogether 18 haploids were regenerated from 2836 embryos, with a maximum efficiency of 1.96% haploids per cross. Obtained haploids were chromosome doubled with mitosis inhibitors trifluralin and oryzalin; exposure to 0.05 g L-1 oryzalin during one week was the most efficient treatment to regenerate doubled haploids. Inbreeding effects in vitro were limited, but the ploidy level affects morphology. Transcriptome sequencing revealed two unique copies of…
Here we describe the ways in which the sequence and annotation of the Plasmodium falciparum reference genome has changed since its publication in 2002. As the malaria species responsible for the most deaths worldwide, the richness of annotation and accuracy of the sequence are important resources for the P. falciparum research community as well as the basis for interpreting the genomes of subsequently sequenced species. At the time of publication in 2002 over 60% of predicted genes had unknown functions. As of March 2019, this number has been significantly decreased to 33%. The reduction is due to the inclusion of…
Members of the genus Juglans are monecious wind-pollinated trees in the family Juglandaceae with highly heterozygous genomes, which greatly complicates genome sequence assembly. The genomes of interspecific hybrids are usually comprised of haploid genomes of parental species. We exploited this attribute of interspecific hybrids to avoid heterozygosity and sequenced an interspecific hybrid Juglans microcarpa?×?J. regia using a novel combination of single-molecule sequencing and optical genome mapping technologies. The resulting assemblies of both genomes were remarkably complete including chromosome termini and centromere regions. Chromosome termini consisted of arrays of telomeric repeats about 8?kb long and heterochromatic subtelomeric regions about 10?kb long.…
In recent genome analyses, population-specific reference panels have indicated important. However, reference panels based on short-read sequencing data do not sufficiently cover long insertions. Therefore, the nature of long insertions has not been well documented. Here, we assembled a Japanese genome using single-molecule real-time sequencing data and characterized insertions found in the assembled genome. We identified 3691 insertions ranging from 100?bps to ~10,000?bps in the assembled genome relative to the international reference sequence (GRCh38). To validate and characterize these insertions, we mapped short-reads from 1070 Japanese individuals and 728 individuals from eight other populations to insertions integrated into GRCh38. With…
The recent release of genomic sequences for 3000 rice varieties provides access to the genetic diversity at species level for this crop. We take advantage of this resource to unravel some features of the retrotranspositional landscape of rice. We develop software TRACKPOSON specifically for the detection of transposable elements insertion polymorphisms (TIPs) from large datasets. We apply this tool to 32 families of retrotransposons and identify more than 50,000 TIPs in the 3000 rice genomes. Most polymorphisms are found at very low frequency, suggesting that they may have occurred recently in agro. A genome-wide association study shows that these activations…
In this presentation, Andrew Clark from Cornell University describes work from a collaboration with Manyuan Long of the University of Chicago and Rod Wing of the University of Arizona to look at heterochromatic regions with long simple satellite repeats in drosophila genomes. The group used PacBio sequencing to create new genome assemblies of 10 drosophila species, including de novo assemblies of two individual flies using as little as 26 ng of gDNA.
To start Day 1 of the PacBio User Group Meeting, Jonas Korlach, PacBio CSO, provides an update on the latest releases and performance metrics for the Sequel II System. The longest reads generated on this system with the SMRT Cell 8M now go beyond 175,000 bases, while maintaining extremely high accuracy. HiFi mode, for example, uses circular consensus sequencing to achieve accuracy of Q40 or even Q50.
Simon Chan, UC Davis on how PacBio long read sequencing revealed higher order repeats in centromeres of switchgrass which would have been hidden if you are restricted by the much shorter Sanger reads.