Single Nucleotide Polymorphisms in Growth Hormone Gene and Their Association with Growth Traits in Siniperca chuatsi (Basilewsky)

Growth hormone (GH) has been considered as a candidate gene for growth traits in fish. In this study, polymorphisms of the GH gene were evaluated for associations with growth traits in 282 Siniperca chuatsi individuals. Using directly sequencing, four single nucleotide polymorphisms (SNPs) were identified in GH gene, with two mutations in intron 4 (g.4940A>C, g.4948A>T), one mutation in exon 5 (g.5045T>C) and one in intron 5 (g.5234T>G). Notably, three of them were significantly associated with growth performance, particularly for g.4940A>C which was highly correlated with all the four growth traits. In conclusion, our results demonstrated that these SNPs in GH gene could influence growth performance of S.chuatsi and could be used for marker-assisted selection (MAS) in this species.     

鳜鱼致敏蛋白的识别及酶法水解的脱敏分析

试验采用聚丙烯酰胺凝胶电泳对鳜鱼蛋白提取液中不同分子质量的蛋白组分进行分离,在阳性血清池建立的基础上,运用转移电泳、免疫印迹以及免疫印迹抑制试验识别特异性吸附蛋白条带。进而采取不同来源的6种食品级蛋白酶对鳜鱼蛋白水解脱敏,将中性甲醛电位滴定法和间接酶联免疫吸附法测定的水解度和抗原降低率作为评判指标优选出最佳水解酶。最终得到分子质量为60、50、34 ku和17 ku的4条蛋白条带可以与IgE阳性结合,最佳水解酶为木瓜蛋白酶。     

广东与湖南养殖鳜群体随机扩增多态DNA研究

采用RAPD技术对广东和湖南养殖鳜群体进行了遗传多样性分析。从40个随机引物中筛选出22个有效引物,共扩增产生289条RAPD标记片段,广东养殖群体共产生155条扩增片段,湖南养殖群体共产生134条扩增片段,有122条带为两群体共有。广东和湖南养殖群体内平均遗传距离分别为0.063 3和0.062 9,两群体间遗传距离为0.129 9。广东和湖南养殖群体Shannon多样性值分别为0.069 0和0.072 3,多态座位比例分别为25.16%和10.15%。与脊椎动物平均多态座位比例比较,发现其遗传多样性并不很丰富。因此,需要在生产过程中要采取行之有效的管理措施以避免或减少遗传多样性水平的降低,确保鳜养殖业的可持续发展。     

基于响应面分析法优化顶空-固相微萃取与气相色谱-质谱法检测黑龙江野生鳜挥发性风味物质

目的 使用响应面分析法优化顶空-固相微萃取(headspace-solid phase microextraction,HS-SPME)与气相色谱-质谱法(gas chromatography-mass spectrometry,GC-MS)联合检测黑龙江鳜肌肉风味的萃取方法,并检测分析鳜肌肉中挥发性风味物质。方法 使用HS-SPME-GC-MS技术,以峰面积和峰个数为指标进行单因素实验,探究盐度、萃取温度、萃取时间和解吸时间对鳜肌肉风味检测的萃取效率的影响,根据单因素实验结果采用响应面方法优化萃取条件,分析鳜肌肉中挥发性风味物质的最佳萃取条件,并用优化后的萃取条件检测鳜的挥发性风味物质。结果 优化后的最佳萃取条件为盐度7.7%,萃取温度82.4℃、萃取时间46.5 min、解吸时间5.4 min。此条件下,综合评分为101.4173,共检测出33种挥发性风味物质,其中化合物含量最多的是烃类和醇类。结论 优化后的HS-SPME-GC-MS分析鳜肌肉挥发性风味物质的方法可以高效萃取鳜肌肉中的风味物质。     

Purification and characterisation of trypsins from the pyloric caeca of mandarin fish (Siniperca chuatsi)

Two trypsins of anionic form (trypsin A) and cationic form (trypsin B) from the pyloric caeca of mandarin fish (Siniperca chuatsi) were highly purified by a series of chromatographies, including DEAE-Sephacel, Sephacryl S-200 HR, Q-Sepharose or SP-Sepharose. Purified trypsins revealed a single band on native-PAGE. The molecular weights of trypsin A and B were 21 kDa and 21.5 kDa, respectively, as estimated by SDS–PAGE, both under reducing and non-reducing conditions. Zymography analysis showed that both trypsins were active in degrading casein. Trypsin A and B exhibited maximal activity at 35 °C and 40 °C, respectively, and shared the same optimal pH of 8.5, using Boc-Phe-Ser-Arg-MCA as substrate. The two trypsins were stable up to 45 °C and in the pH range from 4.5 to 11.0. Trypsin inhibitors are effective on these two enzymes and their susceptibilities were similar. Both trypsins were activated by metal ions such as Ca²⁺ and Mg²⁺ and inactivated by Fe²⁺, Zn²⁺, Mn²⁺, Cu²⁺, Al³⁺, Ba²⁺ and Co²⁺ to different degrees. Apparent K_m values of trypsin A and B were 2.18 μM and 1.88 μM, and K_cat values were 81.6 S⁻¹ and 111.3 S⁻¹ for Boc-Phe-Ser-Arg-MCA, respectively. Immunoblotting analysis using anti-common carp trypsin A positively cross-reacted with the two enzymes, suggesting their similarity. The N-terminal amino acid sequence of trypsin B was determined as IVGGYECEAH, which is highly homologous with trypsins from other species of fish.     

Screening of Genes Related to Sex Determination and Differentiation in Mandarin Fish (Siniperca chuatsi)

Mandarin fish has an XX/XY sex-determination system. The female mandarin fish is typically larger than the male. Sex identification and the discovery of genes related to sex determination in mandarin fish have important theoretical significance in the elucidation of the regulation and evolutionary mechanism of animal reproductive development. In this study, the chromosome-level genome of a female mandarin fish was assembled, and we found that LG24 of the genome was an X chromosome. A total of 61 genes on the X chromosome showed sex-biased expression. Only six gonadal genes (LG24G00426, LG24G003280, LG24G003300, LG24G003730, LG24G004200, and LG24G004770) were expressed in the testes, and the expression of the other gene LG24G003870 isoform 1 in the ovaries was significantly higher than that in the testes (p < 0.01). Five (except LG24G003280 and LG24G003300) of the seven aforementioned genes were expressed at the embryonic development stage, suggesting their involvement in early sex determination. The expression of LG24G004770 (encoding HS6ST 3-B-like) was also significantly higher in female muscles than in male muscles (p < 0.01), indicating other functions related to female growth. ZP3 encoded by LG24G003870 isoform 1 increased the C-terminal transmembrane domain, compared with that encoded by other fish zp3 isoforms, indicating their different functions in sex determination or differentiation. This study provides a foundation for the identification of sex-determining genes in mandarin fish.     

Identification of the aroma compounds in stinky mandarin fish (Siniperca chuatsi) and comparison of volatiles during fermentation and storage

Identification of aroma compounds in Stinky Mandarin fish (Siniperca chuatsi) and comparison of volatiles during fermentation (with spices and salt) and storage were analysed by electronic nose (e‐nose) combining with gas chromatography–mass spectrometry (GC‐MS). Among the sixty‐one detected volatiles, thirteen aroma‐active compounds, especially linalool, were identified in stinky mandarin fish according to thresholds and concentrations. Totally, twenty‐four aroma compounds correlated well with the periods of fermentation and storage. Trimethylamine, indole, sulphur‐containing compounds, acetic acid, esters and phenols increased continually, while aldehydes decreased. According to these quality indicators, e‐nose data using principal component analysis showed a clear discrimination of the fermented fish and were in good agreement with the results of GC‐MS. In conclusion, fermentation favoured to retard spoilage and provided new aroma compounds. The technique employing an e‐nose in combination with GC‐MS could compare and identify the aroma and quality of stinky mandarin fish.