牙鲆连续四代减数分裂雌核发育家系的遗传特征分析

Genetic Analysis of Four Generations of a Successive Meiogynogenetic Population in the Japanese Flounder, Paralichthys olivaceus

中文关键词: 牙鲆  微卫星  雌核发育克隆系  遗传多样性  杂合位点

英文关键词: Paralichthys olivaceus  SSR  Gynogenesis clonal line  Genetic diversity  Heterozygous locus

中文摘要:

      为了研究纯合度和遗传相似度在牙鲆(Paralichthys olivaceus)连续四代减数分裂雌核发育家系中的变化规律，本研究利用分布在不同连锁群上的24个高重组率微卫星标记对牙鲆连续减数分裂雌核发育二代(G2)、三代(G3)、四代(G4)家系及普通家系对照组进行了遗传分析。结果显示，24个微卫星位点在对照组、G2、G3、G4家系中，分别检测到96、42、32和32个等位基因，平均等位基因数分别为4.00、1.98、1.33和1.33；期望杂合度分别为0.6416、0.3472、0.1694和0.1492；纯合度分别为0.3503、0.6528、0.8306和0.8508；遗传相似系数分别为0.5822、0.9238、0.9890和0.9988。24个位点中已有17个纯合，但尚有7个保持杂合状态。同时，将上述结果和已发表的减数分裂雌核发育一代(G1)家系的数据进行分析，结果表明，诱导连续减数分裂雌核发育不仅能提高个体的纯合度，同时也可提高子代个体间的遗传相似度；纯合度和遗传相似度在G1、G2和G3家系中能够得到逐步提高，代际之间差异显著(P<0.05)；但在G4家系中趋于稳定，与G3家系差异不显著。G4家系的遗传相似性(0.9988)已高于连续20代全同胞交配所获得的理论值(0.9860)，连续诱导减数分裂雌核发育是快速建立鱼类近交系的良好方法。

英文摘要:

      Artificially induced gynogenesis is a form of chromosome manipulation for sex control, accelerating both the elimination of recessive deleterious genes and the rapid establishment of inbred lines that could benefit the breeding progress in fish species. Artificially induced gynogenesis can be divided by mechanism into meiogynogenesis and mitogynogenesis. In this study, the fourth generation of a successive meiogynogenetic population (G4) in Japanese flounder (Paralichthys olivaceus) was established by induction of meiogynogenesis, in which the eggs of third-generation females (G3) were activated by ultraviolet-irradiated red sea bream (Pagrus major) sperm, followed by a cold-shock treatment at 0℃, starting 3 min after activation and lasting 45 min. We evaluated the genetic structure of the control, G2, G3, and G4 populations with 24 microsatellite markers and a high recombination rate that covered all linkage groups of the flounder. The efficiency of successive meiogynogenesis in terms of producing a highly inbred line was quantified by calculating the homozygosity and genetic similarity. The results showed that 96, 42, 32, and 32 alleles were detected in the control, G2, G3, and G4 populations, respectively; the average numbers of alleles were 4.00, 1.98, 1.33, and 1.33, respectively; and the average expected heterozygosities were 0.6416, 0.3472, 0.1694, and 0.1492, respectively. The average homozygosities among the 24 analyzed loci were 0.3503, 0.6528, 0.8306, and 0.8508, respectively. In the G4 population, 17 loci were homozygous, while 7 remained heterozygous. With respect to genetic similarity, the average similarity indexes between offsprings within populations were 0.5822, 0.9238, 0.9890, and 0.9988, respectively. Among G1, G2, and G3 populations, the homozygosity and genetic similarity index increased significantly (P<0.05) with generations. However, the differences in homozygosity and genetic similarity index between G3 and G4 were not significant. Our results indicate that artificially induced successive meiogynogenesis can effectively increase the homozygosity of individuals, as well as the genetic similarity of offspring within a population. Successive meiogynogenesis has a higher induction rate than mitogynogenesis, and therefore is a useful alternative method for establishing clonal lines in fish.