Sequence-based estimation of genetic diversity of Plasmodium falciparum, the most lethal malarial parasite, has proved challenging due to a lack of a complete genomic assembly. The skewed AT-richness (~80.6% (A+T)) of its genome and the lack of technology to assemble highly polymorphic sub-telomeric regions that contain clonally variant, multigene virulence families (i.e. var and rifin) have confounded attempts using short-read NGS technologies. Using single molecule, real-time (SMRT) sequencing, we successfully compiled all 14 nuclear chromosomes of the P. falciparum genome from telomere-to-telomere in single contigs. Specifically, amplification-free sequencing generated reads of average length 12 kb, with =50% of the reads…
A high-quality reference genome is an essential resource for primary and applied research across the tree of life. Genome projects for small-bodied, non-model organisms such as insects face several unique challenges including limited DNA input quantities, high heterozygosity, and difficulty of culturing or inbreeding in the lab. Recent progress in PacBio library preparation protocols, sequencing throughput, and read accuracy address these challenges. We present several case studies including the Red Admiral (Vanessa atalanta), Monarch Butterfly (Danaus plexippus), and Anopheles malaria mosquitoes that highlight the benefits of sequencing single individuals for de novo genome assembly projects, and the ease at which…
In this webinar, Emily Hatas of PacBio shares information about the applications and benefits of SMRT Sequencing in plant and animal biology, agriculture, and industrial research fields. This session contains an overview of several applications: whole-genome sequencing for de novo assembly; transcript isoform sequencing (Iso-Seq) method for genome annotation; targeted sequencing solutions; and metagenomics and microbial interactions. High-level workflows and best practices are discussed for key applications.
In this presentation, Sonja Vernes of the Max Plank Institute shares her work with the Bat1K project which aims to catalog the genetic diversity of all living bat species. She highlights the unique biology of bats, from their widely varying sizes to their capacity for healthy aging and disease resistance and provides recent findings from ongoing efforts to sequence and annotate the genomes of 21 phylogenetic families of bats.
In this PacBio User Group Meeting lightning talk, Alexandra Pike of MIT presents a study of TIN2, a telomere-binding protein, which is mutated in some short telomere syndromes. By pairing the Iso-Seq method with CRISPR, her team revealed a previously uncharacterized TIN2 isoform that may have a functional difference for individuals with these syndromes.
In this LabRoots webinar, Jonas Korlach the CSO of PacBio provides an introduction to PacBio HiFi sequence reads, which are both long (up to 25 kb currently) and accurate (>99%) at the individual single-molecule sequence read level andhave allowed for advances in de novo genome assemblies. Korlach reviews the characteristics of HiFi read data obtained with the Sequel II System, followed by examples of high-quality genome assemblies for human, plant and animal genomes including the different aspects of evaluating genome assemblies (contiguity, accuracy, completeness and allelic phasing) and illustrates their high quality by examples of resolving centromeres, telomeres, segmental duplications…
Tina Graves-Lindsay from the McDonnell Genome Institute reports at AGBT 2020 on how her team is using PacBio sequencing to produce reference-grade human genome assemblies. With highly accurate HiFi reads, no error correction step is needed during the sequencing and analysis process, and they can produce reference-grade assemblies with half the sequence coverage needed before. They are now generating diploid assemblies and will be contributing to the human pangenome reference project.
In this webinar you will hear how several researchers have overcome the challenges of sequencing organisms with small body size using the new low and ultra-low DNA input methods from PacBio. Learn about the advantages of using highly accurate long reads (HiFi reads) to sequence and de novo assemble genomes of single individuals.
The sequence and assembly of human genomes using long-read sequencing technologies has revolutionized our understanding of structural variation and genome organization. We compared the accuracy, continuity, and gene annotation of genome assemblies generated from either high-fidelity (HiFi) or continuous long-read (CLR) datasets from the same complete hydatidiform mole human genome. We find that the HiFi sequence data assemble an additional 10% of duplicated regions and more accurately represent the structure of tandem repeats, as validated with orthogonal analyses. As a result, an additional 5 Mbp of pericentromeric sequences are recovered in the HiFi assembly, resulting in a 2.5-fold increase in…
Neisseria gonorrhoeae, the sole causative agent of gonorrhea, constitutively undergoes diversification of the Type IV pilus. Gene conversion occurs between one of the several donor silent copies located in distinct loci and the recipient pilE gene, encoding the major pilin subunit of the pilus. A guanine quadruplex (G4) DNA structure and a cis-acting sRNA (G4-sRNA) are located upstream of the pilE gene and both are required for pilin antigenic variation (Av). We show that the reduced sRNA transcription lowers pilin Av frequencies. Extended transcriptional elongation is not required for Av, since limiting the transcript to 32 nt allows for normal…
After nearly two decades of improvements, the current human reference genome (GRCh38) is the most accurate and complete vertebrate genome ever produced. However, no one chromosome has been finished end to end, and hundreds of unresolved gaps persist. The remaining gaps include ribosomal rDNA arrays, large near-identical segmental duplications, and satellite DNA arrays. These regions harbor largely unexplored variation of unknown consequence, and their absence from the current reference genome can lead to experimental artifacts and hide true variants when re-sequencing additional human genomes. Here we present a de novo human genome assembly that surpasses the continuity of GRCh38, along…
Forest tree species are increasingly subject to severe mortalities from exotic pests, diseases, and invasive organisms, accelerated by climate change. Forest health issues are threatening multiple species and ecosystem sustainability globally. While sources of resistance may be available in related species, or among surviving trees, introgression of resistance genes into threatened tree species in reasonable time frames requires genome-wide breeding tools. Asian species of chestnut (Castanea spp.) are being employed as donors of disease resistance genes to restore native chestnut species in North America and Europe. To aid in the restoration of threatened chestnut species, we present the assembly of…
Haplotype-resolved genome assemblies are important for understanding how combinations of variants impact phenotypes. These assemblies can be created in various ways, such as use of tissues that contain single-haplotype (haploid) genomes, or by co-sequencing of parental genomes, but these approaches can be impractical in many situations. We present FALCON-Phase, which integrates long-read sequencing data and ultra-long-range Hi-C chromatin interaction data of a diploid individual to create high-quality, phased diploid genome assemblies. The method was evaluated by application to three datasets, including human, cattle, and zebra finch, for which high-quality, fully haplotype resolved assemblies were available for benchmarking. Phasing algorithm accuracy…
Satellite repeats are a structural component of centromeres and telomeres, and in some instances their divergence is known to drive speciation. Due to their highly repetitive nature, satellite sequences have been understudied and underrepresented in genome assemblies. To investigate their turnover in great apes, we studied satellite repeats of unit sizes up to 50?bp in human, chimpanzee, bonobo, gorilla, and Sumatran and Bornean orangutans, using unassembled short and long sequencing reads. The density of satellite repeats, as identified from accurate short reads (Illumina), varied greatly among great ape genomes. These were dominated by a handful of abundant repeated motifs, frequently…
TIN2 is an important regulator of telomere length, and mutations in TINF2, the gene encoding TIN2, cause short-telomere syndromes. While the genetics underscore the importance of TIN2, the mechanism through which TIN2 regulates telomere length remains unclear. Here, we tested the effects of human TIN2 on telomerase activity. We identified a new isoform in human cells, TIN2M, that is expressed at levels similar to those of previously studied TIN2 isoforms. All three TIN2 isoforms localized to and maintained telomere integrity in vivo, and localization was not disrupted by telomere syndrome mutations. Using direct telomerase activity assays, we discovered that TIN2…