作为一种雌性异配鱼类（ZW/ZZ），半滑舌鳎雌鱼生长速度是雄鱼的2-4倍，表现出显著的性别大小异形。申请人已选取半滑舌鳎生长-生殖轴组织进行了转录组分析，揭示性类固醇激素可能参与调控半滑舌鳎性别大小异形。据此，本项目拟聚焦雌二醇、睾酮等性类固醇激素，研究半滑舌鳎在性类固醇激素处理后的生长、生殖性能变化情况，采用转录组及DNA甲基化测序手段研究半滑舌鳎生长-生殖轴对性类固醇激素的转录和表观响应模式，从中鉴定影响性别大小异形的关键基因；利用定量PCR、原位杂交等方法揭示关键基因在半滑舌鳎不同性别、发育时期及组织的表达模式，通过甲基化分析、免疫共沉淀等技术研究关键基因的表观、转录及蛋白互作调控机制；采取基因组编辑、RNA干扰等方法揭示关键基因在半滑舌鳎细胞系、组织或成体水平的作用机制。项目成果将有助于揭示性类固醇激素调控半滑舌鳎性别大小异形的分子机制，为培育半滑舌鳎快速生长品系提供理论指导。

As a female heterogamete fish, Chinese tongue sole (Cynoglossus semilaevis) exhibits obvious sexual size dimorphism and the female individuals are 2-4 times bigger than male individuals and pseudomale individuals. We have selected somatotropic and reproductive endocrine axis related tissues (brain, pituitary, liver and gonad) of Chinse tongue sole for RNA-seq analysis. The results suggest that sex steroid hormones may participate the sexual size dimorphism of Chinese tongue sole. This project will focus on sex steroid hormones including estradiol and testosterone, analyze the growth and reproductive trait of Chinese tongue sole treated by sex steroid hormones, and study the transcriptional and epigenetic mechanism of Chinese tongue sole somatotropic and reproductive endocrine axis response to sex steroid hormones via high-throughput sequencing. Then the key genes will be identified from these data. The expression patterns of these key genes in different sex, different developmental stages and different tissues will be revealed by qRT-PCR and in situ hybridization. Also, their epigenetic modification, transcriptional regulation and protein interaction network will be further clarified by DNA methylation and Co-IP analysis. Finally, their functions in sexual size dimorphism will be elucidated by genome editing and RNAi from cell line, tissue or adult levels. The results of this project will be helpful to reveal the molecular mechanism of sex steroid hormones' regulation on sexual size dimorphism of Chinese tongue sole and provide theoretical guide for breeding fast growth strains.