Phylogenetic Position of the Genus Alulacris (Orthoptera: Acrididae: Melanoplinae: Podismini) Revealed by Complete Mitogenome Evidence

Whole mitogenomes are a useful data source for a wide variety of research goals due to the vastly cheaper sequencing cost and the far less demanding high-quality templates. The mitogenome has demonstrated great potential in resolving phylogenetic questions in Orthoptera at different taxonomic scales as well as exploring patterns of molecular and morphological character evolutions. In this study, the complete mitogenome of Alulacris shilinensis (Zheng, 1977) was sequenced using next-generation sequencing, the characteristics of the mitogenome are presented briefly, and the phylogeny of the Melanoplinae and Catantopinae was reconstructed using a selected dataset of mitogenome sequences under maximum likelihood and Bayesian inference frameworks. The results show that the genus was consistently assigned to the subfamily Melanoplinae rather than Catantopinae in all phylogenetic trees deduced from different datasets under different frameworks, and this finding is entirely consistent with its morphological characters. Therefore, it is more appropriate to place the genus Alulacris in Melanoplinae rather than in Catantopinae.

ONTbarcoder and MinION barcodes aid biodiversity discovery and identification by everyone, for everyone

Background DNA barcodes are a useful tool for discovering, understanding, and monitoring biodiversity which are critical tasks at a time of rapid biodiversity loss. However, widespread adoption of barcodes requires cost-effective and simple barcoding methods. We here present a workflow that satisfies these conditions. It was developed via “innovation through subtraction” and thus requires minimal lab equipment, can be learned within days, reduces the barcode sequencing cost to < 10 cents, and allows fast turnaround from specimen to sequence by using the portable MinION sequencer. Results We describe how tagged amplicons can be obtained and sequenced with the real-time MinION sequencer in many settings (field stations, biodiversity labs, citizen science labs, schools). We also provide amplicon coverage recommendations that are based on several runs of the latest generation of MinION flow cells (“R10.3”) which suggest that each run can generate barcodes for > 10,000 specimens. Next, we present a novel software, ONTbarcoder, which overcomes the bioinformatics challenges posed by MinION reads. The software is compatible with Windows 10, Macintosh, and Linux, has a graphical user interface (GUI), and can generate thousands of barcodes on a standard laptop within hours based on only two input files (FASTQ, demultiplexing file). We document that MinION barcodes are virtually identical to Sanger and Illumina barcodes for the same specimens (> 99.99%) and provide evidence that MinION flow cells and reads have improved rapidly since 2018. Conclusions We propose that barcoding with MinION is the way forward for government agencies, universities, museums, and schools because it combines low consumable and capital cost with scalability. Small projects can use the flow cell dongle (“Flongle”) while large projects can rely on MinION flow cells that can be stopped and re-used after collecting sufficient data for a given project.

cLoops2: a full-stack comprehensive analytical tool for chromatin interactions

Investigating chromatin interactions between regulatory regions such as enhancer and promoter elements is vital for a deeper understanding of gene expression regulation. The emerging 3D mapping technologies focusing on enriched signals such as Hi-TrAC/TrAC-looping, compared to Hi-C and variants, reduce the sequencing cost and provide higher interaction resolution for cis-regulatory elements. A robust pipeline is needed for the comprehensive interpretation of these data, especially for loop-centric analysis. Therefore, we have developed a new versatile tool named cLoops2 for the full-stack analysis of the 3D chromatin interaction data. cLoops2 consists of core modules for peak-calling, loop-calling, differentially enriched loops calling and loops annotation. Additionally, it also contains multiple modules to carry out interaction resolution estimation, data similarity estimation, features quantification and aggregation analysis, and visualization. cLoops2 with documentation and example data are open source and freely available at GitHub: https://github.com/YaqiangCao/cLoops2.

Evaluation of whole-genome DNA methylation sequencing library preparation protocols

Background With rapidly dropping sequencing cost, the popularity of whole-genome DNA methylation sequencing has been on the rise. Multiple library preparation protocols currently exist. We have performed 22 whole-genome DNA methylation sequencing experiments on snap frozen human samples, and extensively benchmarked common library preparation protocols for whole-genome DNA methylation sequencing, including three traditional bisulfite-based protocols and a new enzyme-based protocol. In addition, different input DNA quantities were compared for two kits compatible with a reduced starting quantity. In addition, we also present bioinformatic analysis pipelines for sequencing data from each of these library types. Results An assortment of metrics were collected for each kit, including raw read statistics, library quality and uniformity metrics, cytosine retention, and CpG beta value consistency between technical replicates. Overall, the NEBNext Enzymatic Methyl-seq and Swift Accel-NGS Methyl-Seq kits performed quantitatively better than the other two protocols. In addition, the NEB and Swift kits performed well at low-input amounts, validating their utility in applications where DNA is the limiting factor. Results The NEBNext Enzymatic Methyl-seq kit appeared to be the best option for whole-genome DNA methylation sequencing of high-quality DNA, closely followed by the Swift kit, which potentially works better for degraded samples. Further, a general bioinformatic pipeline is applicable across the four protocols, with the exception of extra trimming needed for the Swift Biosciences’s Accel-NGS Methyl-Seq protocol to remove the Adaptase sequence.

Accel-Align: a fast sequence mapper and aligner based on the seed–embed–extend method

Background Improvements in sequencing technology continue to drive sequencing cost towards $100 per genome. However, mapping sequenced data to a reference genome remains a computationally-intensive task due to the dependence on edit distance for dealing with INDELs and mismatches introduced by sequencing. All modern aligners use seed–filter–extend methodology and rely on filtration heuristics to reduce the overhead of edit distance computation. However, filtering has inherent performance–accuracy trade-offs that limits its effectiveness. Results Motivated by algorithmic advances in randomized low-distortion embedding, we introduce SEE, a new methodology for developing sequence mappers and aligners. While SFE focuses on eliminating sub-optimal candidates, SEE focuses instead on identifying optimal candidates. To do so, SEE transforms the read and reference strings from edit distance regime to the Hamming regime by embedding them using a randomized algorithm, and uses Hamming distance over the embedded set to identify optimal candidates. To show that SEE performs well in practice, we present Accel-Align an SEE-based short-read sequence mapper and aligner that is 3–12$$\times$$ × faster than state-of-the-art aligners on commodity CPUs, without any special-purpose hardware, while providing comparable accuracy. Conclusions As sequencing technologies continue to increase read length while improving throughput and accuracy, we believe that randomized embeddings open up new avenues for optimization that cannot be achieved by using edit distance. Thus, the techniques presented in this paper have a much broader scope as they can be used for other applications like graph alignment, multiple sequence alignment, and sequence assembly.

MinION barcodes: biodiversity discovery and identification by everyone, for everyone

DNA barcodes are a useful tool for discovering, understanding, and monitoring biodiversity. This is critical at a time when biodiversity loss is a major problem for many countries. However, widespread adoption of barcoding programs requires the process to be cost-effective and simple to apply. We here present a workflow that satisfies these conditions. It was developed via “innovation through subtraction” and thus requires minimal lab equipment, can be learned within days, reduces the barcode sequencing cost to <10 cents, and allows fast turnaround from specimen to sequence by using the real-time sequencer MinION. We first describe cost-effective and rapid procedures in a comprehensive workflow for obtaining tagged amplicons. We then demonstrate how a portable MinION device can be used for real-time sequencing of tagged amplicons in many settings (field stations, biodiversity labs, citizen science labs, schools). Small projects can use the flow cell dongle (“Flongle”) while large projects can rely on MinION flow cells that can be stopped and re-used after collecting sufficient data for a given project. We also provide amplicon coverage recommendations that are based on several runs of MinION flow cells (R10.3) involving >24,000 specimen barcodes, which suggest that each run can generate >10,000 barcodes. Additionally, we present a novel software, ONTbarcoder, that overcomes the bioinformatics challenges posed by the sequencing errors of MinION reads. This software is compatible with Windows10, Macintosh, and Linux, has a graphical user interface (GUI), and can generate thousands of barcodes on a standard laptop within hours based on two input files (FASTQ, demultiplexing file). Next, we document that MinION barcodes are virtually identical to Sanger and Illumina barcodes for the same specimens (>99.99%). Lastly, we demonstrate how rapidly MinION data have improved by comparing the performance of sequential flow cell generations. We overall assert that barcoding with MinION is the way forward for government agencies, universities, museums, and schools because it combines low consumable and capital cost with scalability. Biodiversity loss is threatening the planet and the use of MinION barcodes will help with enabling an army of researchers and citizen scientists, which is necessary for effective biodiversity discovery and monitoring.

Evaluation of Whole-Genome DNA Methylation Sequencing Library Preparation Protocols

Background: With rapidly dropping sequencing cost, the popularity of whole-genome DNA methylation sequencing has been on the rise. Multiple library preparation protocols exist, but a systematic evaluation and benchmarking of their performance against each other is currently lacking. We have performed 22 whole-genome DNA methylation sequencing experiments on fresh frozen human samples, and extensively benchmarked common library preparation protocols for whole-genome DNA methylation sequencing, including three traditional bisulfite-based protocols and a new enzyme-based protocol. Additionally, different input DNA quantities were compared for two kits compatible with a reduced starting quantity. In addition, we also present bioinformatic analysis pipelines for sequencing data from each of these library types. Results: An assortment of metrics were collected for each kit, including raw read statistics, library quality and uniformity metrics, cytosine retention, and CpG beta value consistency between technical replicates. Overall, the NEBNext Enzymatic Methyl-seq kit performed quantitatively better than the other three protocols at two different DNA input amounts. Additionally, the results for the different input amounts were generally consistent across all metrics. Conclusions: Based on these results, we recommend use of the NEBNext Enzymatic Methyl-seq kit for whole-genome DNA methylation sequencing. Further, a general bioinformatic pipeline is applicable across the four protocols, with the exception of extra trimming needed for the Swift Bioscience's Accel-NGS Methyl-Seq protocol to remove the Adaptase sequence.

Optimized use of Oxford Nanopore flowcells for hybrid assemblies

Hybrid assemblies are highly valuable for studies of Enterobacteriaceae due to their ability to fully resolve the structure of mobile genetic elements, such as plasmids, which are involved in the carriage of clinically important genes (e.g. those involved in antimicrobial resistance/virulence). The widespread application of this technique is currently primarily limited by cost. Recent data have suggested that non-inferior, and even superior, hybrid assemblies can be produced using a fraction of the total output from a multiplexed nanopore [Oxford Nanopore Technologies (ONT)] flowcell run. In this study we sought to determine the optimal minimal running time for flowcells when acquiring reads for hybrid assembly. We then evaluated whether the ONT wash kit might allow users to exploit shorter running times by sequencing multiple libraries per flowcell. After 24 h of sequencing, most chromosomes and plasmids had circularized and there was no benefit associated with longer running times. Quality was similar at 12 h, suggesting that shorter running times are likely to be acceptable for certain applications (e.g. plasmid genomics). The ONT wash kit was highly effective in removing DNA between libraries. Contamination between libraries did not appear to affect subsequent hybrid assemblies, even when the same barcodes were used successively on a single flowcell. Utilizing shorter run times in combination with between-library nuclease washes allows at least 36 Enterobacteriaceae isolates to be sequenced per flowcell, significantly reducing the per-isolate sequencing cost. Ultimately this will facilitate large-scale studies utilizing hybrid assembly, advancing our understanding of the genomics of key human pathogens.