半滑舌鳎是我国近海养殖的重要经济鱼类，其生长是进行遗传改良最有价值的经济性状之一，但是生长的分子遗传基础尚不明了。同龄半滑舌鳎雌性个体比雄性个体大2-4倍，呈现典型的性别生长二态性，是研究雌雄生长差异分子机制的理想模型。外显子捕获测序能够实现多个个体整个外显子组内SNP标记的开发和分型，是研究基因多态性和生长性状相关性的有效手段。本申请项目将对生长速度出现明显分离的F2家系进行外显子捕获测序，构建全部由基因内SNP组成的高密度遗传连锁图谱（<1 cM），将连锁分析和关联分析相结合，分别对半滑舌鳎雌雄生长性状精细QTL定位。通过分析雌雄生长性状重叠及差异的QTL，鉴别调控半滑舌鳎生长及雌雄生长差异的关键基因。这将为解析半滑舌鳎生长的分子机制提供基础，对揭示鱼类雌雄生长差异具有重要的科学意义，还将为半滑舌鳎的分子设计育种提供理论依据。

Half-smooth tongue sole is one of the most economically important marine fish in Chinese coastal waters. Fast growth is an important and desired trait to improve its production, which is a major interest in aquaculture. Although some studies on tongue sole growth have been carried out, the molecular and genetic basis of growth traits remains fragmentary and needs to be clarified. In addition, female tongue sole grows 2-4 times faster than male, providing an ideal model for studying the mechanism of sexual growth dimorphism. SNPs located within genes can be developed and genotyped in many individuals by exome capture sequencing, which provides a high efficient platform to study the association between genotype with growth traits. In this project, we plan to carry out an exome capture sequencing on tongue sole F2 family. Based on SNPs identified by sequencing, a high density linkage map will be constructed. Then, female and male growth traits QTL will be mapped separately. SNPs on or near QTL will be applied to association study in four populations to improve the accuracy of QTL detection. SNPs associated with growth and sexual growth dimorphism will be identified by comparing the overlap and distinguished QTL between female and male growth QTL. Thus, the key gene controlling growth and sexual growth dimorphism will be identified. This will lay the foundation for the mechanism study of growth and sexual growth dimorphism in tongue sole. Furthermore, the markers could be applied to molecular design breeding in tongue sole.

本研究课题的主要目标是筛选半滑舌鳎雌雄生长差异的分子标记。通过构建混合群体，对雌性大小个体、雄性大小个体重测序，全基因关联分析的方法筛选与生长性状显著相关的SNP位点。筛选得到有效SNP位点6,545,735个，其中控制雌性生长差异的显著性SNP位点为1377个（P<0.01），定位到47个基因。集中分布在Z染色体的显著性位点有258个，该结果提示我们，半滑舌鳎WW个体不活，也许跟Z染色体上有多个调控生长的基因有关。控制雄性生长差异的显著性SNP位点为18700个（P<0.01），定位到601个基因。另外，雌、雄显著性SNP位点共同定位到27个基因，经注释分析，这些基因主要与肌动蛋白细胞骨架的调节、脂类和蛋白质代谢、心脏功能及机体免疫等相关。本课题的研究结果对揭示半滑舌鳎雌雄生长差异具有重要意义，同时为培育生长快速半滑舌鳎品系提供理论依据。