Genome and transcriptome assemblies of the kuruma shrimp, Marsupenaeus japonicus

The kuruma shrimp Marsupenaeus japonicus (order Decapoda, family Penaeidae) is an economically important crustacean that occurs in shallow, warm seas across the Indo-Pacific. Here, using a combination of Illumina and Oxford Nanopore Technologies platforms, we produced a draft genome assembly of M. japonicus (1.70 Gbp; 18,210 scaffolds; scaffold N50=234.9 kbp; 34.38% GC, 93.4% BUSCO completeness) and a complete mitochondrial genome sequence (15,969 bp). As with other penaeid shrimp genomes, the M. japonicus genome is extremely rich in simple repeats, which occupies 27.4% of the assembly. A total of 26,381 protein-coding gene models (94.7% BUSCO completeness) were predicted, of which 18,005 genes (68.2%) were assigned functional description by at least one method. We also produced an Illumina-based transcriptome shotgun assembly (40,991 entries; 93.0% BUSCO completeness) and a PacBio Iso-Seq transcriptome assembly (25,415 entries; 67.5% BUSCO completeness). We envision that the M. japonicus genome and transcriptome assemblies will serve as useful resources for the basic research, fisheries management, and breeding programs of M. japonicus.

Identification and Molecular Characterization of a Novel Non-typical Carlavirus Infecting Rose Plants (Rosa Chinensis Jacq.)

In the present study, systematic screening of public transcriptomic data followed by a shotgun assembly from Rosa chinensis Jacq. revealed a sequence of 8,332 nucleotides (nt) representing a potential novel virus, tentatively named rose virus C (RVC). The incidence of RVC in rose plants under our survey was low (5.4%, 5 out of 92). The complete nucleotide sequence of RVC was determined by Sanger sequencing. The genomic RNA of RVC consists of 8,386 nt, excluding the 3′-poly(A) tail, and contains five definite open reading frames (ORFs). BlastN analysis revealed that RVC had 67.3-71.3% nt identity with the carlaviruses with the maximum coverage of 19%. Phylogenetic analysis showed that RVC clustered with the carlaviruses and had a nt sequence identity of 48.3-50.0% based on its full-length genome. Replication protein had 48.7-51.0% nt sequence identity with other carlaviruses while the coat protein showed 39.5-45.6% nt identity being much below the species demarcation criteria of 72%. These all indicate that RVC is a distinct carlavirus. Overall, our data suggest that RVC is a novel non-typical virus species of the genus Carlavirus.

A Crowdsourced Gameplay for Whole-Genome Assembly via Short Reads

Next-generation sequencing has revolutionized the field of genomics by producing accurate, rapid and cost-effective genome analysis with the use of high throughput sequencing technologies. This has intensified the need for accurate and performance efficient genome assemblers to assemble a large set of short reads produced by next-generation sequencing technology. Genome assembly is an NP-hard problem that is computationally challenging. Therefore, the current methods that rely on heuristic and approximation algorithms to assemble genomes prevent them from arriving at the most accurate solution. This paper presents a novel approach by gamifying whole-genome shotgun assembly from next-generation sequencing data; we present "Geno", a human-computing game designed with the aim of improving the accuracy of whole-genome shotgun assembly. We evaluate the feasibility of crowdsourcing the problem of whole-genome shotgun assembly by breaking the problem into small subtasks. The evaluation results, for single-cell Escherichia coli K-12 substr. MG1655 with a read length of 25 bp that produced 144,867 game instances of mean 25 sequences per instance at 40x coverage indicate the feasibility of sub-tasking the problem of genome assembly to be solved using crowdsourcing.<br /><br />

miRNA Identification from Jatropha curcas L. whole genome shotgun assembly sequences

miRNAs are 20-25 nucleotide in length, endogenous in origin, and noncoding RNA molecules found in all the eukaryotic organism and takes part in the regulation of gene expression. Jatropha curcas L. oil has drawn attention as one of the most potential biofuels that can be a substitute of never-ending fuel crisis. Six miRNA candidates, each belonging to different miRNA families were predicted after screening of 41,790 whole genome shotgun assembly sequences by using the comparative genomics approach. The targets of identified miRNA were also predicted, the predicted target genes are belonging to diverse functions like in metabolism, transport, and genes involved in fatty acid metabolism. The predicted miRNAs show their targets which involve in the fatty acid metabolism, like miR414 targets the gene of acetyl-CoA carboxylase and O-acyltransferase WSD1, miR846 targets gene of FAD omega-3 fatty acid, FAD plastid fatty acid desaturase, miR5658 have the target gene long chain acyl-CoA synthetase 1, and miR407 have the target gene Trigalactosyldiacylglycerol 2, miR2938 GDSL esterase/lipase, glycolipid transfer protein 1.

Characterization of a Novel Ourmia-Like Mycovirus Infecting Magnaporthe oryzae and Implications for Viral Diversity and Evolution

Here, the molecular characterization of a novel mycovirus that was isolated from a phytopathogenic fungus Magnaporthe oryzae and designed as Magnaporthe oryzae ourmia-like virus 4 (MOLV4) is reported. MOLV4 has a genome that is 2497 bp long and possesses a single open reading frame (ORF), which encodes the product RNA-dependent RNA polymerase (RdRp). Sequence similarities were found between the MOLV4 encoded RdRp and the counterparts of a few previously reported ourmia-like mycoviruses. Virus-curing and biological comparison indicate that the virus has no or mild effects on the morphology and mycelium growth rate of the host fungus. Phylogenetic analysis using the RdRp aa sequences was performed. The results show that MOLV4 is clustered with the ourmia-like mycoviruses, forming a clade closely related to ourmiaviruses but distinct from narnaviruses. In addition, database searches revealed that several MOLV4-related sequences are present in the transcriptome shotgun assembly (TSA) library, expressed sequence tag database (ESTdb), whole-genome shotgun (WGS) library, and genomic survey sequences (GSS) libraries of a few other species of eukaryote organisms. Our results show that MOLV4, together with other similar ourmia-like mycoviruses, might represent a virus clade that links the plant ourmiaviruses and fungal narnaviruses and has a wide range of hosts.

A Linear Threshold for Uniqueness of Solutions to Random Jigsaw Puzzles

We consider a problem introduced by Mossel and Ross (‘Shotgun assembly of labeled graphs’, arXiv:1504.07682). Suppose a random n × n jigsaw puzzle is constructed by independently and uniformly choosing the shape of each ‘jig’ from q possibilities. We are given the shuffled pieces. Then, depending on q, what is the probability that we can reassemble the puzzle uniquely? We say that two solutions of a puzzle are similar if they only differ by a global rotation of the puzzle, permutation of duplicate pieces, and rotation of rotationally symmetric pieces. In this paper, we show that, with high probability, such a puzzle has at least two non-similar solutions when 2 ⩽ q ⩽ 2e−1/2n, all solutions are similar when q ⩾ (2+ϵ)n, and the solution is unique when q = ω(n).

Phylogenetic approaches to identifying fragments of the same gene, with application to the wheat genome

As the time and cost of sequencing decrease, the number of available genomes and transcriptomes rapidly increases. Yet the quality of the assemblies and the gene annotations varies considerably and often remains poor, affecting downstream analyses. This is particularly true when fragments of the same gene are annotated as distinct genes and consequently wrongly appear as paralogs. In this study, we introduce two novel phylogenetic tests to infer non-overlapping or partially overlapping genes that are in fact parts of the same gene. One approach collapses branches with low bootstrap support and the other computes a likelihood ratio test. We extensively validated these methods by 1) introducing and recovering fragmentation on the bread wheat, Triticum aestivum cv. Chinese Spring, chromosome 3B; 2) by applying the methods to the low-quality 3B assembly and validating predictions against the high-quality 3B assembly; and 3) by comparing the performance of the proposed methods to the performance of existing methods, namely Ensembl Compara and ESPRIT. Application of this combination to a draft shotgun assembly of the entire bread wheat genome revealed 1221 pairs of genes which are highly likely to be fragments of the same gene. Our approach demonstrates the power of fine-grained evolutionary inferences across multiple species to improving genome assemblies and annotations. An open source software tool is available at https://github.com/DessimozLab/esprit2.