Reproductive and Genetic Studies in Large Yellow Croaker

Large yellow croaker (Larimichthys crocea) is distributed in the coastal regions of East Asia and is one of the most important marine aquaculture species in China. However, due to overfishing, it has been difficult to capture wild fish for the last decades. Artificial reproduction and aquaculture of it has been performed since 1985 in China, but important production traits have been deteriorating due to poor broodstock practices. It is thus considered necessary to initiate a modern breeding programme to improve these traits through an efficient selection programme, and the facilitations of this thus became the aim of this PhD project. In paper I, two trials with artificial fertilisation in large yellow croaker were tested and compared. Results show that double injections of LHRH A3 (dosage 0.8 μg/kg and 2 μg/kg ) in females with an interval of 10 h, and single injection (dosage 1μg/kg) in males gave highest fertilisation and hatching percentage. The best latency time (a time period between first hormone injection and spawning) was 29.5-35 h, which were determined by only monitoring courtship behaviour of males to reduce stress. Compared to the initial trial, the percentage of females with spawning difficulties decreased from 30% to 10%, while the fertilisation rate and hatching rate increased from 28% to 41% and from 52% to 62%, respectively. The new protocol of artificial fertilisation will be useful in family construction of future breeding programmes. In paper II, phenotypic and genetic parameters were estimated for body weight, body length and body height in six months old large yellow croaker. The trial was planned to run until the fish had reached a normal harvest size, but due to severe damages to the test facility during a typhon, the trial had to be ended prematurely. The records used for parameter estimation thus are from when the fish were tagged, at an age of only 6 months. The estimates of heritability, which ranged from 0.31±0.06 to 0.41±0.07, may thus be influenced also by common environmental effects unique to each family prior to tagging. The three traits recorded were closely correlated, both genetically and phenotypically, with all genetic correlations above 0.74 and phenotypic correlations above 0.84. These results thus clearly indicate good prospects for efficient selection for BW, BL and BH in large yellow croaker. XII In paper III, a high-density genetic linkage map was constructed using a family from a cross of the Mindong and Daiqu strains. A total of 20,147 single nucleotide polymorphisms (SNPs) markers were assigned to 24 linkage groups (LGs). The length of the consensus linkage map was 1757.4 cM, with individual LGs ranging from 51.9cM (LG6) to 124.6cM (LG9). Sex-specific maps were also constructed, and recombination events occurred 20% more frequently in females. Collapsed or co-occurring markers in the genetic maps were re ordered according to their relative positions in the ASM435267v1 genome assembly to produce integrated linkage maps, resulting in 9,885 SNPs distributed across the 24 LGs. The recombination patterns of most LGs were sigmoidal, with higher recombination rates in the middle and suppressed recombination rates at the ends, consistent with sub-telocentric and acrocentric chromosomes, respectively. The average recombination rate in the integrated female and male maps was respectively 3.55 cM/Mb and 3.05 cM/Mb, as recombination rates in the females were higher than in the males for most LGs. No significant quantitative trait loci (QTL) for growth traits at six months were detected in the QTL or association analyses. The study indicates there may be genetic differences between the Daiqu strain and Mindong strain that can be important for application of genetic tools in a mixed breeding population

Construction of Genetic Linkage Maps From a Hybrid Family of Large Yellow Croaker (Larimichthys crocea)

publishedVersio

New fault tolerance method for open-phase PMSM

Once the motor stator winding is opened, balanced three-phase windings turn into unbalanced two-phases windings. Unfortunately, by conducting Clarke and Park transformation for open-phase PMSM, complete decoupling of the torque and flux cannot achieve. To maintain the rated torque, the two remained phase currents have to be modified as sinusoidal currents with 60◦ phase difference (not 120◦). As a result, the current controller design becomes complicated. In order to solve this problem, a new fault tolerance method for the open-phase PMSM is proposed in this paper. It is designed based on a novel reference frame transformation. Through proposed frame transformation, the modified sinusoidal time-varying current commands are turned into dc variables in the redefined synchronous rotating frame. Hence, the design of the open-phase PMSM current controller can be simplified. This method can deal with different phase open fault and different current control mode (id = 0 or id 6= 0 mode). In addition, considering that the neutral current ripple at usual switching frequencies may be very high, an optimal additional inductance that inserted into the neutral wire is designed. With the designed additional inductance, complete decoupling can be achieved. Experimental results confirm that the reliability and the performance of the PMSM drive can be improved distinctly with the proposed open-phase fault tolerance strategy

Lithium, an anti-psychotic drug, greatly enhances the generation of induced pluripotent stem cells

Somatic cells can be reprogrammed into induced pluripotent stem cells (iPSCs) by defined factors. The low efficiency of reprogramming and genomic integration of oncogenes and viral vectors limited the potential application of iPSCs. Here we report that Lithium (Li), a drug used to treat mood disorders, greatly enhances iPSC generation from both mouse embryonic fibroblast and human umbilical vein endothelial cells. Li facilitates iPSC generation with one (Oct4) or two factors (OS or OK). The effect of Li on promoting reprogramming only partially depends on its major target GSK3β. Unlike other GSK3β inhibitors, Li not only increases the expression of Nanog, but also enhances the transcriptional activity of Nanog. We also found that Li exerts its effect by promoting epigenetic modifications via downregulation of LSD1, a H3K4-specific histone demethylase. Knocking down LSD1 partially mimics Li's effect in enhancing reprogramming. Our results not only provide a straightforward method to improve the iPSC generation efficiency, but also identified a histone demethylase as a critical modulator for somatic cell reprogramming

Reproductive and Genetic Studies in Large Yellow Croaker

Large yellow croaker (Larimichthys crocea) is distributed in the coastal regions of East Asia and is one of the most important marine aquaculture species in China. However, due to overfishing, it has been difficult to capture wild fish for the last decades. Artificial reproduction and aquaculture of it has been performed since 1985 in China, but important production traits have been deteriorating due to poor broodstock practices. It is thus considered necessary to initiate a modern breeding programme to improve these traits through an efficient selection programme, and the facilitations of this thus became the aim of this PhD project. In paper I, two trials with artificial fertilisation in large yellow croaker were tested and compared. Results show that double injections of LHRH A3 (dosage 0.8 μg/kg and 2 μg/kg ) in females with an interval of 10 h, and single injection (dosage 1μg/kg) in males gave highest fertilisation and hatching percentage. The best latency time (a time period between first hormone injection and spawning) was 29.5-35 h, which were determined by only monitoring courtship behaviour of males to reduce stress. Compared to the initial trial, the percentage of females with spawning difficulties decreased from 30% to 10%, while the fertilisation rate and hatching rate increased from 28% to 41% and from 52% to 62%, respectively. The new protocol of artificial fertilisation will be useful in family construction of future breeding programmes. In paper II, phenotypic and genetic parameters were estimated for body weight, body length and body height in six months old large yellow croaker. The trial was planned to run until the fish had reached a normal harvest size, but due to severe damages to the test facility during a typhon, the trial had to be ended prematurely. The records used for parameter estimation thus are from when the fish were tagged, at an age of only 6 months. The estimates of heritability, which ranged from 0.31±0.06 to 0.41±0.07, may thus be influenced also by common environmental effects unique to each family prior to tagging. The three traits recorded were closely correlated, both genetically and phenotypically, with all genetic correlations above 0.74 and phenotypic correlations above 0.84. These results thus clearly indicate good prospects for efficient selection for BW, BL and BH in large yellow croaker. XII In paper III, a high-density genetic linkage map was constructed using a family from a cross of the Mindong and Daiqu strains. A total of 20,147 single nucleotide polymorphisms (SNPs) markers were assigned to 24 linkage groups (LGs). The length of the consensus linkage map was 1757.4 cM, with individual LGs ranging from 51.9cM (LG6) to 124.6cM (LG9). Sex-specific maps were also constructed, and recombination events occurred 20% more frequently in females. Collapsed or co-occurring markers in the genetic maps were re ordered according to their relative positions in the ASM435267v1 genome assembly to produce integrated linkage maps, resulting in 9,885 SNPs distributed across the 24 LGs. The recombination patterns of most LGs were sigmoidal, with higher recombination rates in the middle and suppressed recombination rates at the ends, consistent with sub-telocentric and acrocentric chromosomes, respectively. The average recombination rate in the integrated female and male maps was respectively 3.55 cM/Mb and 3.05 cM/Mb, as recombination rates in the females were higher than in the males for most LGs. No significant quantitative trait loci (QTL) for growth traits at six months were detected in the QTL or association analyses. The study indicates there may be genetic differences between the Daiqu strain and Mindong strain that can be important for application of genetic tools in a mixed breeding population

Artificial fertilization and generating families for a selective breeding programme of large yellow croaker (Larimichthys crocea)

publishedVersio

Construction of Genetic Linkage Maps From a Hybrid Family of Large Yellow Croaker (Larimichthys crocea)

Consensus and sex-specific genetic linkage maps for large yellow croaker (Larimichthys crocea) were constructed using samples from an F(1) family produced by crossing a Daiqu female and a Mindong male. A total of 20,147 single nucleotide polymorphisms (SNPs) by restriction site associated DNA sequencing were assigned to 24 linkage groups (LGs). The total length of the consensus map was 1757.4 centimorgan (cM) with an average marker interval of 0.09 cM. The total length of female and male linkage map was 1533.1 cM and 1279.2 cM, respectively. The average female-to-male map length ratio was 1.2 ± 0.23. Collapsed markers in the genetic maps were re-ordered according to their relative positions in the ASM435267v1 genome assembly to produce integrated genetic linkage maps with 9885 SNPs distributed across the 24 LGs. The recombination pattern of most LGs showed sigmoidal patterns of recombination, with higher recombination in the middle and suppressed recombination at both ends, which corresponds with the presence of sub-telocentric and acrocentric chromosomes in the species. The average recombination rate in the integrated female and male maps was respectively 3.55 cM/Mb and 3.05 cM/Mb. In most LGs, higher recombination rates were found in the integrated female map, compared to the male map, except in LG12, LG16, LG21, LG22, and LG24. Recombination rate profiles within each LG differed between the male and the female, with distinct regions indicating potential recombination hotspots. Separate quantitative trait loci (QTL) and association analyses for growth related traits in 6 months fish were performed, however, no significant QTL was detected. The study indicates that there may be genetic differences between the two strains, which may have implications for the application of DNA-information in the further breeding schemes

A fast and robust open-switch fault diagnosis method for variable-speed PMSM system

Traditional open-switch fault diagnosis methods suffer from poor rapidity or robustness. To solve this issue, a new differential current observer-based fault diagnosis method is proposed in this article. With the designed differential observer, fault symptoms (residuals) can be generated and adopted for fault diagnosis easily. Considering that the residuals are sensitive to motor operating condition in the conventional model-based method due to model error, an adaptive fault detection threshold is designed. As a result, the false detection and missed detection caused by the change of working condition can be avoided, and stronger robustness against speed, load, and parameter variations can be achieved with superior rapidity compared with existing methods. Finally, the rapidity and robustness of the proposed fault diagnosis method are verified sufficiently through experimental results