Ion Torrent data for the genome assembly and phylogenomic placement of mitochondrial genomes with a focus on houndsharks (Chondrichthyes: Triakidae)

Here, we present, for the first time, the Ion TorrentⓇ next-generation sequencing (NGS) data for five houndsharks (Chondrichthyes: Triakidae), which include Galeorhinus galeus (number of bases pairs (bp) 17,487; GenBank accession number ON652874), Mustelus asterias (16,708; ON652873), Mustelus mosis (16,755; ON075077), Mustelus palumbes (16,708; ON075076), and Triakis megalopterus (16,746; ON075075). All assembled mitogenomes encode 13 protein-coding genes (PCGs), two ribosomal (r)RNA genes, and 22 transfer (t)RNA genes (tRNALeu and tRNASer are duplicated), except for G. galeus which contains 23 tRNA genes where tRNAThr is duplicated. The data presented in this paper can assist other researchers in further elucidating the diversification of triakid species and the phylogenetic relationships within Carcharhiniformes (groundsharks) as mitogenomes accumulate in public repositories.


Value of the Data
Presents five newly assembled houndshark mitochondrial genomes used in the mitophylogenomic investigation in Winn et al. [2] , with potential to contribute to population genomics investigations, species phylogeography delineation, and environmental DNA metabarcoding databases.

Background
Complex evolutionary patterns in the mitochondrial genome (mitogenome) of the most species-rich order, the Carcharhiniforms (groundsharks) has yielded challenges in phylogenomic reconstruction of families and genera belonging to it, particularly in the family Triakidae (hound- sharks), where there are arguments for both monophyly and paraphyly.We hypothesized that opposing resolutions are a product of the a priori partitioning scheme selected.Accordingly, we sequenced and assembled five new mitogenomes to expand the houndshark mitogenome repository and used them in the reconstruction of the mitochondrial phylogenomic relationships within Carcharhiniforms.In the paper by Winn et al. [2] , we used an extensive statistical pipeline to select a suitable partitioning scheme for inference of the mitochondrial phylogenomic relationships within Carcharhiniforms and used the multi-species coalescent model to account for the influence of gene tree discordance on species tree inference.The Ion Torrent mitogenome reads and available mitogenomes presented here can be used to further clarify the phylogenetic relationships within Triakidae as mitogenomes accumulate in public repositories.

Data Description
A total of 38,889,488 unpaired raw reads with an average of 315 bp per read were generated from the whole genome shotgun sequencing of five triakid species with the Ion GeneStudio TM S5 Prime System ( Table 1 ).The raw sequencing data for the whole genome has been uploaded as a BioProject onto the SRA database, but it has been suppressed until release of a related manuscript.Table 1 displays the difference in length of mitogenomes assembled using the reference and 'hybrid' techniques, whereby the reads that mapped to the reference mitogenome were fed into a de novo assembly pipeline.

Ion genestudio TM S5 data processing
For the five houndshark species for which sequencing data was generated, sequence quality was checked in FastQC and adaptors and poor-quality bases (Phred score below 20) were trimmed and reads shorter than 25 bp were removed in Torrent Suite Version 5.16.Raw reads were aligned to the Mustelus mustelus mitogenome (NC_039629.1;[3] ) using the Geneious read mapper with medium sensitivity settings and five iterations in Geneious Prime (version 2019.1.3)[4] .The reads that mapped to the reference mitogenome were then saved in BAM format as filtered Ion Torrent reads (Data 1-5).These filtered reads were fed into a de novo assembly pipeline ('hybrid' assembly) in SPAdes v.3.15 [5] with the input set for unpaired Ion Torrent reads with 8 threads, kmers 21,33,55,77,99,127, the careful option to reduce the number of mismatches and short indels and all other parameters left as default.The resulting complete mitochondrial genomes for each houndshark species were annotated using MitoAnnotator in MitoFish v. 3.85 [ 6 , 7 ] and deposited on GenBank.The process of filtering reads using a reference mitogenome and then mapping the filtered reads de novo produced a higher quality assembly, minimising reference-bias while reducing the computational demands of straight de novo assembly.
© 2024 The Author(s).Published by Elsevier Inc.This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ ) [1]or SDS-based lysis buffer (PL2) from the NucleoSpin Plant II mini kit (MACHEREY-NAGEL, Dueren, Germany); DNA quality control: Qubit 4.0 fluorometer (ThermoFisher Scientific) and LabChip R GXII Touch (PerkinElmer, Waltham, MA, USA); Library preparation: Ion Plus Fragment Library Kit (ThermoFisher Scientific) according to the manufacturer's protocol, Ion Xpress TM Plus gDNA Fragment Library Preparation User Guide (MAN0 0 09847 K.0); NGS Sequencing: Ion GeneStudio TM S5 Prime System and postprocessing with Torrent Suite version 5.16 under default settings at the Central Analytical Facility (CAF) at Stellenbosch University.Data source locationFin clip tissue samples of Galeorhinus galeus, Mustelus palumbes , and Triakis megalopterus were collected along the coast of South Africa.Mustelus asterias and Mustelus mosis were sampled off the coasts of Wales and the Sultanate of Oman respectively.

Table 1
Summary of Ion Torrent sequencing output and mitogenome assembly statistics for the five newly assembled Triakidae mitogenomes.
a Q: Phred quality score.