褐牙鲆和夏牙鲆杂交的遗传学研究

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	褐牙鲆和夏牙鲆杂交的遗传学研究
其他题名	Genetic characterization of hybridization between olive flounder and summer flounder
	徐冬冬
学位类型	博士
	2009-05-31
学位授予单位	中国科学院海洋研究所
学位授予地点	海洋研究所
关键词	褐牙鲆夏牙鲆正反交回交不对称生殖隔离染色体缺失 Aflp 16s Rdna Coⅰ Rag1
摘要	在进行褐牙鲆(Paralichthys olivaceus)和夏牙鲆(P. dentatus)的杂交及回交的基础上，利用染色体计数、AFLP、线粒体DNA和核基因部分序列等分析方法对褐牙鲆和夏牙鲆正反交和回交子代进行遗传学研究，探讨了褐牙鲆和夏牙鲆正反交不对称的遗传学基础及其生殖隔离现象，主要结果如下： 1. 褐牙鲆和夏牙鲆正反交的活力是不对称的，褐牙鲆♀×夏牙鲆♂的正交杂种活力正常，能够正常存活、生长和发育，而反交夏牙鲆♀×褐牙鲆♂的杂种体态畸形，孵出后不久死亡。染色体计数发现正交个体的染色体核型与父母本一致，均为48条端部着丝粒染色体；而反交杂种比亲本缺失了两条染色体，仅为46条端部着丝粒染色体，这表明反交杂种为非整倍体。进一步利用AFLP方法对遗传物质从亲本到子代的传递进行了分析，结果显示正反交遗传物质的传承方式存在很大差异。几乎所有亲本的AFLP位点(97.71%)均传递到正交子代。然而，仅有86.64%的AFLP位点从亲本传递到反交子代，反交子代中亲本位点的丢失比例显著高于正交子代和亲本种内交配子代的比例 ( P < 0.05)，这可能与反交杂种染色体丢失有关。进一步分析发现，杂交组中的偏分离标记高于对照组，尽管经2检验发现其差异并不显著 (P > 0.05)。 2. 对于可以成活的正交杂种进行培育达到性成熟后，利用褐牙鲆和夏牙鲆的精液分别与雌性杂交鲆的卵子进行母本回交实验。通过统计受精率、孵化率及杂交适合度值（CFM，受精率和孵化率相乘获得的结果）评估褐牙鲆和夏牙鲆的杂交可适度，结果表明正交及各回交组中的CFM值均显著低于褐牙鲆自交(P < 0.05)。同时，利用AFLP对回交子代基因组的变化进行了分析，发现回交中不仅存在亲本位点的丢失(褐牙鲆回交子代-回交1, 3.96%; 夏牙鲆回交子代-回交2, 6.03%)的现象，也存在非亲位点(回交1, 5.63%; 回交2, 3.28%)的现象。而且，两回交组合分别有27.40%和31.18%的AFLP标记偏离孟德尔遗传。 3. 利用线粒体DNA 16S rDNA、COⅠ基因及核基因rag1的部分序列对正反交及回交子代的线粒体及核DNA的传承进行分析，发现正反交子代的16S rDNA和线粒体DNA片段的同源性和母本一致，各回交组中16S rDNA和COⅠ基因片段与褐牙鲆的同源性较高 (98%)，这表明褐牙鲆和夏牙鲆杂交及回交遵循母性遗传规律。但在回交子代中发现16S rDNA和COⅠ基因具有多种单倍型。褐牙鲆和夏牙鲆的rag1基因具有高度的保守性，但在正交子代中发现rag1多种单倍型。 4. 进一步利用线粒体DNA的16S rDNA、COⅠ基因的部分序列对8种重要海水养殖鱼类的系统进化分析，计算了其种间的遗传距离。根据这几种鲆鲽鱼的杂交是否可行的试验结果，评价种间遗传距离与杂交可适度的关系，结果表明，这8种鲆鲽鱼类的种间遗传距离与杂交可适度呈显著的负相关 (r2 = 0.805，P < 0.01)，即种间遗传分化越大，杂交成功的可能性越小，这表明鲆鲽鱼类中可能存在物种进化的不亲和钟 (Incompatibility clock)。
其他摘要	Based on the hybridization and backcross experiments between olive flounder (Paralichthys olivaceus) and summer flounder (P. dentatus), chromosome counting, AFLP, mtDNA and nuclear gene partial sequences were employed to characterize genomic inheritance in these hybrid and backcross offspring. The genetic basis of asymmetric viabilibility in reciprocal hybrids and post-zygotic isolation between olive flounder and summer flounder were studied. The results are as following, 1. Interspecific reciprocal crosses between Paralichthys olivaceus and P. dentatus yielded hybrids with different viabilities. Specifically, the hybrids of P. olivaceus female and P. dentatus male (H1) were found to be viable, while the reciprocal hybrids from P. dentatus female and P. olivaceus male (H2) were completely inviable. All the H2 individuals showed morphological deformities and died before first feeding. The chromosome analysis showed that H1 individuals had the same chromosome number as parents’. However, two chromosomes were missing in H2 offspring indicating that the latter were aneuploids. Genomic inheritance from the parents to F1 progeny was further examined by amplified fragment length polymorphism (AFLP) analyses, and the results indicated differences between reciprocal hybrids. Almost all AFLP bands (97.71%) present in parents were passed on to H1 individuals. In contrast, only 86.64% of the AFLP bands from parents were scored in H2 individuals. And frequency of lost parental bands was significantly higher in H2 than that in H1 and intraspecific crosses, which was probably associated with chromosomal elimination. In addition, higher segregation distortions were found in hybrids than in controls, although these differences were not significant. 2. The H1 hybrids were bred to mature. We performed hybrid and maternal backcross experiments using olive flounder, summer flounder and their female H1 hybrids. Fertilization rates, hatching rates and combined fitness measure (CFM, product of fertilization rate and hatching rate) were calculated to examine the fitness between the two species. The CFMs of hybrid and backcross generations reduced significantly compared to pure olive flounder crosses. We also detected genomic changes which were possibly associated with the reduced fitness in backcross by amplified fragment length polymorphism (AFLP). The changes mainly involved loss of parental AFLP bands (backcross1, F1 hybrid female × olive flounder male, 3.96%; backcross2, F1 hybrid female × summer flounder male, 6.03%) and gaining of novel bands (backcross1, 5.63%; backcross2, 3.28%). Meanwhile, segregation distortions were observed in backcross generations. There were 27.40% and 31.18% of AFLP markers deviating from expected Mendelian ratio in two families, respectively. 3. The transmission of mtDNA 16S rDNA, COⅠand nuclear rag1 partial sequences from parents to hybrid and backcross offspring were also analyzed. The hybrids possess identical sequences of 16S rDNA, COⅠ to their maternal parents. The backcross progeny had high homology with their maternal parents (98%). These finding indicated that mitochondrial 16S rDNA and COⅠ partial sequences in artifical hybrids and backcrosses were inherited maternally. Nevertheless, mutiple haplotypes of 16S rDNA and COⅠ genes were found in backcross. The partial sequences of rag1 gene were identical in olive flounder and summer flounder, while multiple haplotypes of rag1 were found in H1, which was probably involved in recombination or genetic variation in hybrids. 4. A phylogenetic tree was reconstructed based on the partial sequences of 16S rDNA and COⅠgenes in eight commercial flatfishes (Pleuronectiformes). The parameters of pairwise genetic distance among these flatfishes were calculated. Based on the crossing data among these flatfishes, the relationship between pairwise genetic distance and hybrid fitness was evaluated. The findings indicated that positive relationship might exist between genetic distance and hybrid fitness. The pairwise genetic divergence between species decreased as the interspecific hybrid fitness largened. These results implied that speciation clock might exsit in Pleuronectiformes.
页数	121
语种	中文
文献类型	学位论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/365
专题	海洋环流与波动重点实验室
推荐引用方式 GB/T 7714	徐冬冬. 褐牙鲆和夏牙鲆杂交的遗传学研究[D]. 海洋研究所. 中国科学院海洋研究所,2009.

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