Background The swimming crab, Portunus trituberculatus, is an important farmed species in China, has been attracting extensive studies, which require more and more genome background knowledge. To date, the sequencing of its whole genome is unavailable and transcriptomic information is also scarce for this species. In the present study, we performed de novo transcriptome sequencing to produce a comprehensive transcript dataset for major tissues of Portunus trituberculatus by the Illumina paired-end sequencing technology. Results Total RNA was isolated from eyestalk, gill, heart, hepatopancreas and muscle. Equal quantities of RNA from each tissue were pooled to construct a cDNA library. Using the Illumina paired-end sequencing technology, we generated a total of 120,137 transcripts with an average length of 1037 bp. Further assembly analysis showed that all contigs contributed to 87,100 unigenes, of these, 16,029 unigenes (18.40% of the total) can be matched in the GenBank non-redundant database. Potential genes and their functions were predicted by GO, KEGG pathway mapping and COG analysis. Based on our sequence analysis and published literature, many putative genes with fundamental roles in growth and muscle development, including actin, myosin, tropomyosin, troponin and other potentially important candidate genes were identified for the first time in this specie. Furthermore, 22,673 SSRs and 66,191 high-confidence SNPs were identified in this EST dataset. Conclusion The transcriptome provides an invaluable new data for a functional genomics resource and future biological research in Portunus trituberculatus. The data will also instruct future functional studies to manipulate or select for genes influencing growth that should find practical applications in aquaculture breeding programs. The molecular markers identified in this study will provide a material basis for future genetic linkage and quantitative trait loci analyses, and will be essential for accelerating aquaculture breeding programs with this species.
Abstract Exopalaemon carinicauda , a eurythermal and euryhaline shrimp, contributes one third of the total biomass production of polyculture ponds in eastern China and is considered as a potential ideal experimental animal for research on crustaceans. We conducted a high-quality chromosome-level genome assembly of E. carinicauda combining PacBio HiFi and Hi-C sequencing data. The total assembly size was 5.86 Gb, with a contig N50 of 235.52 kb and a scaffold N50 of 138.24 Mb. Approximately 95.29% of the assembled sequences were anchored onto 45 pseudochromosomes. BUSCO analysis revealed that 92.89% of 1,013 single-copy genes were highly conserved orthologs. A total of 44, 288 protein-coding genes were predicted, of which 70.53% were functionally annotated. Given its high heterozygosity (2.62%) and large proportion of repeat sequences (71.49%), it is one of the most complex genome assemblies. This chromosome-scale genome will be a valuable resource for future molecular breeding and functional genomics research on E. carinicauda .
A high-resolution genetic linkage map is an essential tool for decoding genetics and genomics in non-model organisms. In this study, a linkage map was constructed for the swimming crab (Portunus trituberculatus) with 10,963 markers; as far as we know, this number of markers has never been achieved in any other crustacean. The linkage map covered 98.85% of the whole genome with a mean marker interval of 0.51 cM. The de novo assembly based on genome and transcriptome sequencing data enabled 2,378 explicit annotated markers to be anchored to the map. Quantitative trait locus (QTL) mapping revealed 10 growth-related QTLs with a phenotypic variance explained (PVE) range of 12.0-35.9. Eight genes identified from the growth-related QTL regions, in particular, RE1-silencing transcription factor and RNA-directed DNA polymerase genes with nonsynonymous substitutions, were considered important growth-related candidate genes. We have demonstrated that linkage mapping aided by de novo assembly of genome and transcriptome sequencing could serve as an important platform for QTL mapping and the identification of trait-related genes.
Background The swimming crab, Portunus trituberculatus, which is naturally distributed in the coastal waters of Asia-Pacific countries, is an important farmed species in China. Salinity is one of the most important abiotic factors that influence not only the distribution and abundance of crustaceans, it is also an important factor for artificial propagation of the crab. To better understand the interaction between salinity stress and osmoregulation, we performed a transcriptome analysis in the gills of Portunus trituberculatus challenged with salinity stress, using the Illumina Deep Sequencing technology. Results We obtained 27,696,835, 28,268,353 and 33,901,271 qualified Illumina read pairs from low salinity challenged (LC), non-challenged (NC), and high salinity challenged (HC) Portunus trituberculatus cDNA libraries, respectively. The overall de novo assembly of cDNA sequence data generated 94,511 unigenes, with an average length of 644 bp. Comparative genomic analysis revealed that 1,705 genes differentially expressed in salinity stress compared to the controls, including 615 and 1,516 unigenes in NC vs LC and NC vs HC respectively. GO functional enrichment analysis results showed some differentially expressed genes were involved in crucial processes related to osmoregulation, such as ion transport processes, amino acid metabolism and synthesis processes, proteolysis process and chitin metabolic process. Conclusion This work represents the first report of the utilization of the next generation sequencing techniques for transcriptome analysis in Portunus trituberculatus and provides valuable information on salinity adaptation mechanism. Results reveal a substantial number of genes modified by salinity stress and a few important salinity acclimation pathways, which will serve as an invaluable resource for revealing the molecular basis of osmoregulation in Portunus trituberculatus. In addition, the most comprehensive sequences of transcripts reported in this study provide a rich source for identification of novel genes in the crab.
Recent conservation efforts to protect rare and endangered aquatic species have intensified. Nevertheless, the ornate spiny lobster (Panulirus ornatus), which is prevalent in the Indo-Pacific waters, has been largely ignored. In the absence of a detailed genomic reference, the conservation and population genetics of this crustacean are poorly understood. Here, We assembled a comprehensive chromosome-level genome for P. ornatus. This genome-among the most detailed for lobsters-spans 2.65 Gb with a contig N50 of 51.05 Mb, and 99.11% of the sequences with incorporated to 73 chromosomes. The ornate spiny lobster genome comprises 65.67% repeat sequences and 22,752 protein-coding genes with 99.20% of the genes functionally annotated. The assembly of the P. ornatus genome provides valuable insights into comparative crustacean genomics and endangered species conservation, and lays the groundwork for future research on the speciation, ecology, and evolution of the ornate spiny lobster.
Molting is an essential biological process throughout the life history of crustaceans, which is regulated by many neuropeptide hormones expressed in the eyestalk. To better understand the molting mechanism in Portunus trituberculatus, we used digital gene expression (DGE) to analyze single eyestalk samples during the molting cycle by high-throughput sequencing.We obtained 14,387,942, 12,631,508 and 13,060,062 clean sequence reads from inter-molt (InM), pre-molt (PrM) and post-molt (PoM) cDNA libraries, respectively. A total of 1,394 molt-related differentially expressed genes (DEGs) were identified. GO and KEGG enrichment analysis identified some important processes and pathways with key roles in molting regulation, such as chitin metabolism, peptidase inhibitor activity, and the ribosome. We first observed a pattern associated with the neuromodulator-related pathways during the molting cycle, which were up-regulated in PrM and down-regulated in PoM. Four categories of important molting-related transcripts were clustered and most of them had similar expression patterns, which suggests that there is a connection between these genes throughout the molt cycle.Our work is the first molt-related investigation of P. trituberculatus focusing on the eyestalk at the whole transcriptome level. Together, our results, including DEGs, identification of molting-related biological processes and pathways, and observed expression patterns of important genes, provide a novel insight into the function of the eyestalk in molting regulation.
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