Whole genome survey analysis and microsatellite motif identification of Sebastiscus marmoratus

Genome-wide characterization of microsatellites in cobia Rachycentron canadum (Linnaeus, 1766): Survey and analysis of their abundance and diversity

The cobia Rachycentron canadum, mainly distributed in the warm waters of tropical and subtropical regions around the world, remains a fish of considerable economic importance. Detailed diversity and the number of microsatellite sequences in the cobia genome are still unintelligible. The primary aim of this work was to identify and quantify the miscellaneous SSR sequences in the cobia genome. More than 280,000 sequences were sequenced and screened using next-generation sequencing technology and microsatellite identification. Perfect mononucleotide repeats, dinucleotide microsatellites, and trinucleotide microsatellites contain (A)10 /(T)10 , (AC)6 /(TG)6 , and (AAT)5-32 as the largest number of motifs in each type of microsatellite, respectively. The tetranucleotide and pentanucleotide microsatellites (TTM and PTM) consist of the largest number of motifs of both (ATCT)5-32 and (TCAT)5-31 in TTMs, and (CTCTC)5-9 in PTMs, whereas the hexanucleotide microsatellites are rarely observed in the cobia genome. All c. 38000 sequences of composite microsatellites are extremely diverse, including compound (11.71%), interrupted compound (71.77%), complex (0.45%), and interrupted complex (16.07%). In this study, we developed a convenient and useful recording system for writing down and categorizing diverse composite microsatellite types. This system will provide great support for exploring repeat origins, evolutionary mechanisms, and the application of polymorphic microsatellites.

A first insight into the genomic background of Ilex pubescens (Aquifoliaceae) by flow cytometry and genome survey sequencing

BACKGROUND

Ilex pubescens is an important traditional Chinese medicinal plant with many naturally occurring compounds and multiple pharmacological effects. However, the lack of reference genomic information has led to tardiness in molecular biology research and breeding programs of this plant.

RESULTS

To obtain knowledge on the genomic information of I. pubescens, a genome survey was performed for the first time by next generation sequencing (NGS) together with genome size estimation using flow cytometry. The whole genome survey of I. pubescens generated 46.472 Gb of sequence data with approximately 82.2 × coverage. K-mer analysis indicated that I. pubescens has a small genome of approximately 553 Mb with 1.93% heterozygosity rate and 39.1% repeat rate. Meanwhile, the genome size was estimated to be 722 Mb using flow cytometry, which was possibly more precise for assessment of genome size than k-mer analysis. A total of 45.842 Gb clean reads were assembled into 808,938 scaffolds with a relatively short N50 of 760 bp. The average guanine and cytosine (GC) content was 37.52%. In total, 197,429 microsatellite motifs were detected with a frequency of 2.8 kb, among which mononucleotide motifs were the most abundant (up to 62.47% of the total microsatellite motifs), followed by dinucleotide and trinucleotide motifs.

CONCLUSION

In summary, the genome of I. pubescens is small but complex with a high level of heterozygosity. Even though not successfully applied for estimation of genome size due to its complex genome, the survey sequences will help to design whole genome sequencing strategies and provide genetic information support for resource protection, genetic diversity analysis, genetic improvement and artificial breeding of I. pubescens.

Genome-wide survey reveals the phylogenomic relationships of Chirolophisjaponicus Herzenstein, 1890 (Stichaeidae, Perciformes)

Fish are the largest vertebrate group, consisting of more than 30 000 species with important ecological and economical value, while less than 3% of fish genomes have been published. Herein, a fish, Chirolophisjaponicus, was sequenced using the next-generation sequencing. Approximately 595.7 megabase pair of the C.japonicus genome was assembled (49 901 contigs with 42.61% GC contents), leading to a prediction of 46 729 protein-coding gene models. A total of 554 136 simple sequence repeats was identified in the whole genome of C.japonicus, and dinucleotide microsatellite motifs were the most abundant, accounting for 59.49%. Phylogenomic analysis of 16 genomes based on the 694 single-copy genes suggests that C.japonicus is closely related with Anarrhichthysocellatus, Cebidichthysviolaceus, and Pholisgunnellus. The results provide more thorough genetic information of C.japonicus and a theoretical basis and reference for further genome-wide analysis.

Whole-Genome Survey and Microsatellite Marker Detection of Antarctic Crocodile Icefish, Chionobathyscus dewitti

Simple Summary

Crocodile icefish inhabit the deep sea around the Southern Ocean and belong to the family Channichthyidae. The species lacks hemoglobin and has evolved an antifreeze protein, unlike other teleosts. In this study, the whole-genome survey and microsatellite motifs were analyzed, which provide relevant information on genetic diversity, population genetics, and the genomic study of crocodile icefish.

Abstract

The crocodile icefish, Chionobathyscus dewitti, belonging to the family Channichthyidae, is an endemic species of the Southern Ocean. The study of its biological features and genetics is challenging as the fish inhabits the deep sea around Antarctic waters. The icefish, the sole cryopelagic species, shows unique physiological and genetic features, unlike other teleosts. It lacks hemoglobin and has evolved antifreeze proteins. Here, we report the genome sequencing data of crocodile icefish produced using the Illumina Novaseq 6000 platform. The estimated genome size was 0.88 Gb with a K-value of 19, and the unique sequence, heterozygosity, error, and duplication rates were 57.4%, 0.421%, 0.317%, and 0.738%, respectively. A genome assembly of 880.69 Mb, with an N50 scaffold length of 2401 bp, was conducted. We identified 2,252,265 microsatellite motifs from the genome assembly data, and dinucleotide repeats (1,920,127; 85.25%) had the highest rate. We selected 84 primer pairs from the genome survey assembly and randomly selected 30 primer pairs for validation. As a result, 15 primer pairs were validated as microsatellite markers.

Genomic Survey and Microsatellite Marker Investigation of Patagonian Moray Cod (Muraenolepis orangiensis)

Simple Summary

Patagonian moray cod is known to inhabit the cold waters near Antarctica, and it belongs to the Muraenolepis genus. This genus has seven species, and five of them are recently reported. The Muraenolepis genus has similar morphological characters, and this is a limitation of taxonomical classification. In this study, a genome survey and microsatellite marker analysis were conducted to characterize the genome profile for classification. As a result, genomic data such as genome size and microsatellite motifs were obtained.

Abstract

The Muraenolepididae family of fishes, known as eel cods, inhabits continental slopes and shelves in the Southern Hemisphere. This family belongs to the Gadiformes order, which constitutes one of the most important commercial fish resources worldwide, but the classification of the fish species in this order is ambiguous because it is only based on the morphological and habitat characteristics of the fishes. Here, the genome of Patagonian moray cod was sequenced using the Illumina HiSeq platform, and screened for microsatellite motifs. The genome was predicted to be 748.97 Mb, with a heterozygosity rate of 0.768%, via K-mer analysis (K = 25). The genome assembly showed that the total size of scaffolds was 711.92 Mb and the N50 scaffold length was 1522 bp. Additionally, 4,447,517 microsatellite motifs were identified from the genome survey assembly, and the most abundant motif type was found to be AC/GT. In summary, these data may facilitate the identification of molecular markers in Patagonian moray cod, which would be a good basis for further whole-genome sequencing with long read sequencing technology and chromosome conformation capture technology, as well as population genetics.

Comprehensive Draft Genome Analyses of Three Rockfishes (Scorpaeniformes, Sebastiscus) via Genome Survey Sequencing

Sebastiscus species, marine rockfishes, are of essential economic value. However, the genomic data of this genus is lacking and incomplete. Here, whole genome sequencing of all species of Sebastiscus was conducted to provide fundamental genomic information. The genome sizes were estimated to be 802.49 Mb (S. albofasciatus), 786.79 Mb (S. tertius), and 776.00 Mb (S. marmoratus) by using k-mer analyses. The draft genome sequences were initially assembled, and genome-wide microsatellite motifs were identified. The heterozygosity, repeat ratios, and numbers of microsatellite motifs all suggested possibly that S. tertius is more closely related to S. albofasciatus than S. marmoratus at the genetic level. Moreover, the complete mitochondrial genome sequences were assembled from the whole genome data and the phylogenetic analyses genetically supported the validation of Sebastiscus species. This study provides an important genome resource for further studies of Sebastiscus species.

Genome-Wide Survey Reveals the Microsatellite Characteristics and Phylogenetic Relationships of Harpadon nehereus

Harpadon nehereus forms one of the most important commercial fisheries along the Bay of Bengal and the southeast coast of China. In this study, the genome-wide survey dataset first produced using next-generation sequencing (NGS) was used to provide general information on the genome size, heterozygosity and repeat sequence ratio of H. nehereus. About 68.74 GB of high-quality sequence data were obtained in total and the genome size was estimated to be 1315 Mb with the 17-mer frequency distribution. The sequence repeat ratio and heterozygosity were calculated to be 52.49% and 0.67%, respectively. A total of 1,027,651 microsatellite motifs were identified and dinucleotide repeat was the most dominant simple sequence repeat (SSR) motif with a frequency of 54.35%. As a by-product of whole genome sequencing, the mitochondrial genome is a powerful tool to investigate the evolutionary relationships between H. nehereus and its relatives. The maximum likelihood (ML) phylogenetic tree was constructed according to the concatenated matrix of amino acids translated from the 13 protein-coding genes (PCGs). Monophyly of two species of the genus Harpadon was revealed in the present study and they formed a monophyletic clade with Saurida with a high bootstrap value of 100%. The results would help to push back the frontiers of genomics and open the doors of molecular diversity as well as conservation genetics studies on this species.

Whole genome survey and genetic markers development of crocodile flathead Cociella crocodilus

Flatheads in family Platycephalidae are ecologically and commercially important marine fish species in the Indo-West Pacific. Due to similar morphological characters, the taxonomy and phylogenetics of flatheads are in confusion. Studies on phylogenetics and molecular marker development are required to discriminate congeners of flatheads. In the present study, we performed whole genome survey sequencing of crocodile flathead Cociella crocodilus to provide genomic information and genetic markers of this species. In total, 54.03 Gb of clean genomic data were generated. The genome size was estimated to be 732.99 Mb with the heterozygosity ratio of 0.73% and the repeat sequence ratio of 33.48%. The preliminary assembled genome sequences were 794.07 Mb with contig N50 of 1504 bp. We detected 2 624 875 genome-wide SNPs with transition/transversion ratio of 1.422. A total of 313 842 microsatellite motifs were identified, most of which were dinucleotide motifs with a frequency of 74.89%. In addition, we assembled the complete mitogenome of C. crocodilus and subsequent phylogenetic analysis were performed. Phylogenetic analyses revealed numbers of polyphyletic groups in family Platycephalidae. The reported genomic data and genetic markers in our study should be useful in further phylogeny and phylogenomics studies of flathead species.

Genome survey and microsatellite motif identification of Pogonophryne albipinna

The genus Pogonophryne is a speciose group that includes 28 species inhabiting the coastal or deep waters of the Antarctic Southern Ocean. The genus has been divided into five species groups, among which the P. albipinna group is the most deep-living group and is characterized by a lack of spots on the top of the head. Here, we carried out genome survey sequencing of P. albipinna using the Illumina HiSeq platform to estimate the genomic characteristics and identify genome-wide microsatellite motifs. The genome size was predicted to be ∼883.8 Mb by K-mer analysis (K = 25), and the heterozygosity and repeat ratio were 0.289 and 39.03%, respectively. The genome sequences were assembled into 571624 contigs, covering a total length of ∼819.3 Mb with an N50 of 2867 bp. A total of 2217422 simple sequence repeat (SSR) motifs were identified from the assembly data, and the number of repeats decreased as the length and number of repeats increased. These data will provide a useful foundation for the development of new molecular markers for the P. albipinna group as well as for further whole-genome sequencing of P. albipinna.

Genomic characteristics and profile of microsatellite primers for Acanthogobius ommaturus by genome survey sequencing

Acanthogobius ommaturus is one of the suitable species to study the genetic mechanism of adaptive evolution, but there are few reports on its genetics. In the present study, the genomic survey sequencing method was used to analyze the genome characters of A. ommaturus. A total of 50.50 G high-quality sequence data were obtained in the present study. From the 19-mer distribution frequency, the estimated genome size was 928.01 Mb. The calculated sequence repeat rate was about 38.31%, the heterozygosity was approximately 0.17%, and the GC% content was approximately 40.88%. Moreover, 475,724 simple sequence repeats (SSRs) were identified. Among them, dinucleotide repeats were the most (53.70% of the total SSRs), followed by tri- (35.36%), hexa- (4.59%), tetra- (4.57%) and penta- (1.77%) nucleotide repeats type. This is the first genome-wide feature of this species to be reported.

Whole genome survey and microsatellite motif identification of Artemia franciscana

Artemia is an industrially important genus used in aquaculture as a nutritious diet for fish and as an aquatic model organism for toxicity tests. However, despite the significance of Artemia, genomic research remains incomplete and knowledge on its genomic characteristics is insufficient. In particular, Artemia franciscana of North America has been widely used in fisheries of other continents, resulting in invasion of native species. Therefore, studies on population genetics and molecular marker development as well as morphological analyses are required to investigate its population structure and to discriminate closely related species. Here, we used the Illumina Hi-Seq platform to estimate the genomic characteristics of A. franciscana through genome survey sequencing (GSS). Further, simple sequence repeat (SSR) loci were identified for microsatellite marker development. The predicted genome size was ∼867 Mb using K-mer (a sequence of k characters in a string) analysis (K = 17), and heterozygosity and duplication rates were 0.655 and 0.809%, respectively. A total of 421467 SSRs were identified from the genome survey assembly, most of which were dinucleotide motifs with a frequency of 77.22%. The present study will be a useful basis in genomic and genetic research for A. franciscana.

Comprehensive whole genome survey analyses of male and female brown-spotted flathead fish Platycephalus sp.1

The flathead fish Platycephalus sp.1 is an ecologically and commercially important marine fish in the northwestern Pacific with notable sexual differences in growth and development. Yet the genomic data of this species is lacking. In the present study, whole genome sequencing of two individuals (one male and one female) of Platycephalus sp.1 were conducted to provide fundamental genomic information. The genome sizes were estimated to be 674.96 Mb (male) and 684.15 Mb (female) by using k-mer analyses. The heterozygosity and repeat ratios suggested possible male heterogamety of this species. The draft genome sequences were initially assembled and genome-wide microsatellite motifs were identified. Besides, the complete mitochondrial genome sequences were assembled and the phylogenetic analyses genetically supported the validation of Platycephalus sp.1. The reported genomic data and genetic markers in this study could be useful in future comparative genomics and evolutionary biology studies.