Genome-wide analysis facilitates estimation of the amount of male contribution in meiotic gynogenetic three-spined stickleback (Gasterosteus aculeatus)

Gynogenetic embryos - those inheriting only maternal DNA - can be experimentally created by fertilizing eggs with radiation-treated sperm containing inactivated paternal chromosomes. Diploidy in the zygotes can be maintained through prevention of the second meiosis or restored by preventing the first mitosis after the maternal chromosome complement has been replicated. These gynogenetic organisms are useful in many fields including aquaculture, evolutionary biology and genomics. Although gynogenetic organisms have been created in numerous species, the completeness of uni-parental inheritance has often been assumed rather than thoroughly quantified across the genome. Instead, when tests of uni-parental inheritance occur, they typically rely on well-studied genetically determined phenotypes that represent a very small sub-set of the genome. Only assessing small genomic regions for paternal inheritance leaves the question of whether some paternal contributions to offspring might still have occurred. In this study, the authors quantify the efficacy of creating gynogenetic diploid three-spined stickleback fish (Gasterosteus aculeatus). To this end, the authors mirrored previous assessments of paternal contribution using well-studied genetically determined phenotypes including sex and genetically dominant morphological traits but expanded on previous studies using dense restriction site-associated DNA sequencing (RAD-seq) markers in parents and offspring to assess paternal inheritance genome-wide. In the gynogenetic diploids, the authors found no male genotypes underlying their phenotypes of interest - sex and dominant phenotypic traits. Using genome-wide assessments of paternal contribution, nevertheless, the authors found evidence of a small, yet potentially important, amount of paternally "leaked" genetic material. The application of this genome-wide approach identifies the need for more widespread assessment of paternal contributions to gynogenetic animals and promises benefits for many aspects of aquaculture, evolutionary biology and genomics.

Genetic inactivation of European sea bass (Dicentrarchus labrax L.) eggs using UV-irradiation: observations and perspectives

Androgenesis is a form of uniparental reproduction leading to progenies inheriting only the paternal set of chromosomes. It has been achieved with variable success in a number of freshwater species and can be attained by artificial fertilization of genetically inactivated eggs following exposure to gamma (γ), X-ray or UV irradiation (haploid androgenesis) and by restoration of diploidy by suppression of mitosis using a pressure or thermal shock. The conditions for the genetic inactivation of the maternal genome in the European sea bass (Dicentrarchus labrax L.) were explored using different combinations of UV irradiation levels and durations. UV treatments significantly affected embryo survival and generated a wide range of developmental abnormalities. Despite the wide range of UV doses tested (from 7.2 to 720 mJ x cm(-2)), only one dose (60 mJ x cm(-2) x min(-1) with 1 min irradiation) resulted in a small percentage (14%) of haploid larvae at hatching in the initial trials as verified by flow cytometry. Microsatellite marker analyses of three further batches of larvae produced by using this UV treatment showed a majority of larvae with variable levels of paternal and maternal contributions and only one larva displaying pure paternal inheritance. The results are discussed also in the context of an assessment of the UV-absorbance characteristics of egg extracts in this species that revealed the presence of gadusol, a compound structurally related to mycosporine-like amino acids (MAAs) with known UV-screening properties.

Identification and profiling of microRNAs from skeletal muscle of the common carp

The common carp is one of the most important cultivated species in the world of freshwater aquaculture. The cultivation of this species is particularly productive due to its high skeletal muscle mass; however, the molecular mechanisms of skeletal muscle development in the common carp remain unknown. It has been shown that a class of non-coding ∼22 nucleotide RNAs called microRNAs (miRNAs) play important roles in vertebrate development. They regulate gene expression through sequence-specific interactions with the 3' untranslated regions (UTRs) of target mRNAs and thereby cause translational repression or mRNA destabilization. Intriguingly, the role of miRNAs in the skeletal muscle development of the common carp remains unknown. In this study, a small-RNA cDNA library was constructed from the skeletal muscle of the common carp, and Solexa sequencing technology was used to perform high throughput sequencing of the library. Subsequent bioinformatics analysis identified 188 conserved miRNAs and 7 novel miRNAs in the carp skeletal muscle. The miRNA expression profiling showed that, miR-1, miR-133a-3p, and miR-206 were specifically expressed in muscle-containing organs, and that miR-1, miR-21, miR-26a, miR-27a, miR-133a-3p, miR-206, miR-214 and miR-222 were differentially expressed in the process of skeletal muscle development of the common carp. This study provides a first identification and profiling of miRNAs related to the muscle biology of the common carp. Their identification could provide clues leading towards a better understanding of the molecular mechanisms of carp skeletal muscle development.

Genetic linkage mapping and analysis of muscle fiber-related QTLs in common carp (Cyprinus carpio L.)

A genetic linkage map of common carp (Cyprinus carpio L.) was constructed using Type I and Type II microsatellite markers and a pseudo-testcross mapping strategy. The microsatellite markers were isolated from microsatellite-enriched genomic libraries and tested for their segregation in a full-sib mapping panel containing 92 individuals. A total of 161 microsatellite loci were mapped into 54 linkage groups. The total lengths of the female, male and consensus maps were 2,000, 946, and 1,852 cM, with an average marker spacing of approximately 13, 7, and 11 cM, respectively. Muscle fiber-related traits, including muscle fiber cross-section area and muscle fiber density, were mapped to the genetic map. Three QTLs for muscle fiber cross-section area and two QTLs for muscle fiber density were identified when considering both significant and suggestive QTL effects. The QTLs with largest effects for muscle fiber cross-section area and muscle fiber density were 21.9% and 18.9%, and they were located in LG3, respectively.

[Studies on quantitative trait loci related to activity of lactate dehydrogenase in common carp (Cyprinus carpio)]

The reciprocal intergeneric hybrids between common wheat and Roegneria kamoji were successfully obtained by means of embryo culture. Morphology, chromosome pairing behavior at meiosis, fertility, and resistance to scab of the hybrid F1 and BC1 were studied. The results showed that the morphology of the reciprocal intergeneric hybrids F1 between R. kamoji and T. aestivum cv. Chinese Spring were intermediate type between the two parental species. The chromosome configuration at metaphase I (MI) of pollen mother cell (PMC) in reciprocal F1 was 40.33I + 0.78II + 0.03III and 40.40I + 0.79II, respectively. All of the F1 plants showed complete male sterility, and the seeds of BC1 were obtained by backcrossing with Chinese Spring pollen. The somatic chromosome numbers in BC1 plants of (R. kamoji x Chinese Spring) F1 x Chinese Spring ranged from 55 to 63. Many univalents were observed at MI of PMC, which resulted in the sterility of BC1 plants. Similarly, the chromosome numbers in BC1 plants of (Chinese Spring xR. kamoji) F1 x Chinese Spring also ranged from 55 to 63; however, many bivalents at MI of PMC and fertile pollen were observed resulting in partial fruitfulness in some BC1 plants by self-crossing. A plant (2n=63) with 42 wheat chromosomes and 21 R. kamoji chromosomes was obtained from R. kamoji x Chinese Spring cross, which had a chromosome configuration at MI of 26.40I + 18.30II. Because many univalents existed, this plant showed complete male sterility, and BC1 plants were obtained by back-crossing with Chinese Spring as the pollen parent. The chromosome numbers of BC1 ranged from 40 to 59, which contained less alien chromosomes. Although the morphology of the spike in BC1 plants was similar to that of Chinese Spring, these BC1 plants were still sterile. All F1 and most of the BC1 plants showed high resistance to Fusarium graminearum, which indicated that the resistance to scab from R. kmoji can be transferred into wheat.Microsatellite markers were used to make marker regression analysis on activity of lactate dehydrogenase based on double pseudo-testcross strategy using Windows Map Manager2.0 software. The parents that came from the cross between progenies of Hebao-cold tolerance red carp and Barbless carp and F2 progenies were used as segregating populations. For maker regression, a total of 12 markers associated with activity of lactate dehydrogenase were significant at P<0.05 and HLJE222 was significant at P<0.01. The variance explained by these loci, ranged from 4.00% to 10.00%. Locus HLJE222 was closely linked to the gene related to activity of lactate dehydrogenase of common carp. For further identification, EST-SSR markers were used to screen the protein and nucleotide database using bioinformatics tools in order to find the homologies. High sequence similarities of HLJE222 marker were observed with the nucleotide sequence of DAZ associated protein 1mRNA of zebrafish(94%), and protein sequence of DAZ associated protein 1(97%). DAZ protein is one of the short chain dehydrogenases, which is an important enzyme in the process of glucose metabolism in the organisms. This family contains a wide variety of dehydrogenases. This indicates that locus HLJE222 was closely linked to the gene associated with activity of lactate dehydrogenase of common carp.