A set of polymorphic trinucleotide and tetranucleotide microsatellite markers for silver crucian carp (Carassius auratus gibelio) and cross-amplification in crucian carp

An efficient approach to synthesize sterile allopolyploids through the combined reproduction mode of ameiotic oogenesis and sperm-egg fusion in the polyploid Carassius complex

The association between polyploidy and reproduction transition, which is an intriguing issue in evolutionary genetics, can also be exploited as an approach for genetic improvement in agriculture. Recently, we generated novel amphitriploids (NA3n) by integrating the genomes of the gynogenetic Carassius gibelio and sexual C. auratus, and found gynogenesis was recovered in most NA3n females (NA3n♀I). Here, we discovered a unique reproduction mode, termed ameio-fusiongenesis, which combines the abilities of both ameiotic oogenesis and sperm-egg fusion, in a few NA3n females (NA3n♀II). These females inherited ameiotic oogenesis to produce unreduced eggs from gynogenetic C. gibelio and sperm-egg fusion from sexual C. auratus. Subsequently, we utilized this unique reproduction mode to generate a group of synthetic alloheptaploids by crossing NA3n♀II with Megalobrama amblycephala. They contained all chromosomes of maternal NA3n♀II and a chromosomal set of paternal M. amblycephala. Intergenomic chromosome translocations between NA3n♀II and M. amblycephala were also observed in a few somatic cells. Primary oocytes of the alloheptaploid underwent severe apoptosis owing to incomplete double-strand break repair at prophase I. Although spermatocytes displayed similar chromosome behavior at prophase I, they underwent apoptosis due to chromosome separation failure at metaphase I. Therefore, the alloheptaploid females and males were all sterile. Finally, we established a sustainable clone for the large-scale production of NA3n♀II and developed an efficient approach to synthesize diverse allopolyploids containing genomes of different cyprinid species. These findings not only broaden our understanding of reproduction transition but also offer a practical strategy for polyploidy breeding and heterosis fixing.

Genetic Diversity Evaluation and Population Structure Analysis of Red Swamp Crayfish (Procambarus clarkii) from Lakes and Rice Fields by SSR Markers

The red swamp crayfish (Procambarus clarkii) is an important aquatic animal and has developed as a popular aquaculture species in China. In this study, a total of 72,839 SSR motifs were identified from transcriptional data, and 20 microsatellite markers of them were finally developed to assess the genetic diversities of seven wild populations from natural lakes and nine cultured populations from rice fields. Genetic diversity was slightly higher in the cultured populations than in the wild populations. The degree of genetic differentiation between cultured populations is slight, while a moderate to a large degree of genetic differentiation between wild populations and most of the variations occurred within individuals (79%). The analysis of cluster, principal coordinate analysis and STRUCTURE were similar, and they showed that isolation-by-distance pattern was not significant. The microsatellite markers developed in this study can not only be used for genetic monitoring of population but also provide important information for the management of breeding and cultured population in red swamp crayfish.

Embryonic fate after somatic cell nuclear transfer in non-enucleated goldfish oocytes is determined by first cleavages and DNA methylation patterns

Reducing the variability in nuclear transfer outcome requires a better understanding of its cellular and epigenetic determinants, in order to ensure safer fish regeneration from cryobanked somatic material. In this work, clones from goldfish were obtained using cryopreserved fin cells as donor and non-enucleated oocytes as recipients. We showed that the high variability of clones survival was not correlated to spawn quality. Clones were then characterized for their first cleavages pattern in relation to their developmental fate up to hatching. The first cell cycle duration was increased in clones with abnormal first cleavage, and symmetric first two cleavages increased clone probability to reach later on 24 h- and hatching-stages. At 24 h-stage, 24% of the clones were diploids and from donor genetic origin only. However, ploidy and genetic origin did not determine clones morphological quality. DNA methylation reprogramming in the promoter region of pou2, nanog, and notail marker genes was highly variable, but clones with the nicest morphologies displayed the best DNA methylation reprogramming. To conclude, non-enucleated oocytes did allow authentic clones production. The first two cell cycles were a critical determinant of the clone ability to reach hatching-stage, and DNA methylation reprogramming significantly influenced clones morphological quality.

A High-Density Genetic Linkage Map and QTL Fine Mapping for Body Weight in Crucian Carp (Carassius auratus) Using 2b-RAD Sequencing

A high-resolution genetic linkage map is essential for a wide range of genetics and genomics studies such as comparative genomics analysis and QTL fine mapping. Crucian carp (Carassius auratus) is widely distributed in Eurasia, and is an important aquaculture fish worldwide. In this study, a high-density genetic linkage map was constructed for crucian carp using 2b-RAD technology. The consensus map contains 8487 SNP markers, assigning to 50 linkage groups (LGs) and spanning 3762.88 cM, with an average marker interval of 0.44 cM and genome coverage of 98.8%. The female map had 4410 SNPs, and spanned 3500.42 cM (0.79 cM/marker), while the male map had 4625 SNPs and spanned 3346.33 cM (0.72 cM/marker). The average recombination ratio of female to male was 2.13:1, and significant male-biased recombination suppressions were observed in LG47 and LG49. Comparative genomics analysis revealed a clear 2:1 syntenic relationship between crucian carp LGs and chromosomes of zebrafish and grass carp, and a 1:1 correspondence, but extensive chromosomal rearrangement, between crucian carp and common carp, providing evidence that crucian carp has experienced a fourth round of whole genome duplication (4R-WGD). Eight chromosome-wide QTL for body weight at 2 months after hatch were detected on five LGs, explaining 10.1-13.2% of the phenotypic variations. Potential candidate growth-related genes, such as an EGF-like domain and TGF-β, were identified within the QTL intervals. This high-density genetic map and QTL analysis supplies a basis for genome evolutionary studies in cyprinid fishes, genome assembly, and QTL fine mapping for complex traits in crucian carp.

Development of novel tetra- and trinucleotide microsatellite markers for giant grouper Epinephelus lanceolatus using 454 pyrosequencing

Giant grouper (Epinephelus lanceolatus) is a commercially important species, but its wild population has recently been classified as vulnerable. This species has significant potential for use in aquaculture, though a greater understanding of population genetics is necessary for selective breeding programs to minimize kinship for genetically healthy individuals. High-throughput pyrosequencing of genomic DNA was used to identify and characterize novel tetra- and trinucleotide microsatellite markers in giant grouper from Sabah, Malaysia. In total, of 62,763 sequences containing simple sequence repeats (SSRs) were obtained, and 78 SSR loci were selected to possibly contain tetra- and trinucleotide repeats. Of these loci, 16 had tetra- and 8 had trinucleotide repeats, all of which exhibited polymorphisms within easily genotyped regions. A total of 143 alleles were identified with an average of 5.94 alleles per locus, with mean observed and expected heterozygosities of 0.648 and 0.620, respectively. Among of them, 15 microsatellite markers were identified without null alleles and with Hardy-Weinberg equilibrium. These alleles showed a combined non-exclusion probability of 0.01138. The probability of individual identification (PID) value combined with in descending order 12 microsatellite markers was 0.00008, which strongly suggests that the use of the microsatellite markers developed in this study in various combinations would result in a high resolution method for parentage analysis and individual identification. These markers could be used to establish a broodstock management program for giant grouper and to provide a foundation for genetic studies such as population structure, parentage analysis, and kinship selection.

Application of microsatellite markers in conservation genetics and fisheries management: recent advances in population structure analysis and conservation strategies

Microsatellites are the most popular and versatile genetic marker with myriads of applications in population genetics, conservation biology, and evolutionary biology. These are the arrays of DNA sequences, consisting of tandemly repeating mono-, di-, tri-, and tetranucleotide units, which are distributed throughout the genomes of most eukaryotic species. Microsatellites are codominant in nature, highly polymorphic, easily typed, and Mendelian inherited, all properties which make them very suitable for the study of population structure and pedigree analysis and capable of detecting differences among closely related species. PCR for microsatellites can be automated for identifying simple sequence repeat polymorphism. Small amount of blood samples or alcohol preserved tissue is adequate for analyzing them. Most of the microsatellites are noncoding, and therefore variations are independent of natural selection. These properties make microsatellites ideal genetic markers for conservation genetics and fisheries management. This review addresses the applications of microsatellite markers in conservation genetics and recent advances in population structure analysis in the context of fisheries management.

Transcriptome analysis of crucian carp (Carassius auratus), an important aquaculture and hypoxia-tolerant species

The crucian carp is an important aquaculture species and a potential model to study genome evolution and physiological adaptation. However, so far the genomics and transcriptomics data available for this species are still scarce. We performed de novo transcriptome sequencing of four cDNA libraries representing brain, muscle, liver and kidney tissues respectively, each with six specimens. The removal of low quality reads resulted in 2.62 million raw reads, which were assembled as 127,711 unigenes, including 84,867 isotigs and 42,844 singletons. A total of 22,273 unigenes were found with significant matches to 14,449 unique proteins. Around14,398 unigenes were assigned with at least one Gene Ontology (GO) category in 84,876 total assignments, and 6,382 unigenes were found in 237 predicted KEGG pathways. The gene expression analysis revealed more genes expressed in brain, more up-regulated genes in muscle and more down-regulated genes in liver as compared with gene expression profiles of other tissues. In addition, 23 enzymes in the glycolysis/gluconeogenesis pathway were recovered. Importantly, we identified 5,784 high-quality putative SNP and 11,295 microsatellite markers which include 5,364 microsatellites with flanking sequences ≥50 bp. This study produced the most comprehensive genomic resources that have been derived from crucian carp, including thousands of genetic markers, which will not only lay a foundation for further studies on polyploidy origin and anoxic survival but will also facilitate selective breeding of this important aquaculture species.

Analysis of genome survey sequences and SSR marker development for Siamese Mud Carp, Henicorhynchus siamensis, using 454 pyrosequencing

Siamese mud carp (Henichorynchus siamensis) is a freshwater teleost of high economic importance in the Mekong River Basin. However, genetic data relevant for delineating wild stocks for management purposes currently are limited for this species. Here, we used 454 pyrosequencing to generate a partial genome survey sequence (GSS) dataset to develop simple sequence repeat (SSR) markers from H. siamensis genomic DNA. Data generated included a total of 65,954 sequence reads with average length of 264 nucleotides, of which 2.79% contain SSR motifs. Based on GSS-BLASTx results, 10.5% of contigs and 8.1% singletons possessed significant similarity (E value < 10(-5)) with the majority matching well to reported fish sequences. KEGG analysis identified several metabolic pathways that provide insights into specific potential roles and functions of sequences involved in molecular processes in H. siamensis. Top protein domains detected included reverse transcriptase and the top putative functional transcript identified was an ORF2-encoded protein. One thousand eight hundred and thirty seven sequences containing SSR motifs were identified, of which 422 qualified for primer design and eight polymorphic loci have been tested with average observed and expected heterozygosity estimated at 0.75 and 0.83, respectively. Regardless of their relative levels of polymorphism and heterozygosity, microsatellite loci developed here are suitable for further population genetic studies in H. siamensis and may also be applicable to other related taxa.

Genetic analysis of Black Tiger shrimp (Penaeus monodon) across its natural distribution range reveals more recent colonization of Fiji and other South Pacific islands

The Black Tiger shrimp (Penaeus monodon) has a natural distribution range from East Africa to the South Pacific Islands. Although previous studies of Indo-Pacific P. monodon have found populations from the Indian Ocean and Australasia to differ genetically, their relatedness to South Pacific shrimp remains unknown. To address this, polymorphisms at eight shared microsatellite loci and haplotypes in a 418-bp mtDNA-CR (control region) sequence were examined across 682 P. monodon from locations spread widely across its natural range, including the South Pacific islands of Fiji, Palau, and Papua New Guinea (PNG). Observed microsatellite heterozygosities of 0.82-0.91, allele richness of 6.85-9.69, and significant mtDNA-CR haplotype variation indicated high levels of genetic diversity among the South Pacific shrimp. Analysis of microsatellite genotypes using a Bayesian STRUCTURE method segregated Indo-Pacific P. monodon into eight distinct clades, with Palau and PNG shrimp clustering among others from Southeast Asia and eastern Australia, respectively, and Fiji shrimp clustering as a distinct group. Phylogenetic analyses of mtDNA-CR haplotypes delineated shrimp into three groupings, with shrimp from Fiji again being distinct by sharing no haplotypes with other populations. Depending on regional location, the genetic structures and substructures identified from the genotyping and mtDNA-CR haplotype phylogeny could be explained by Metapopulation and/or Member-Vagrant type evolutionary processes. Neutrality tests of mutation-drift equilibrium and estimation of the time since population expansion supported a hypothesis that South Pacific P. monodon were colonized from Southeast Asia and eastern Australia during the Pleistocene period over 60,000 years ago when land bridges were more expansive and linked these regions more closely.