Comparative Transcriptomic Study of Muscle Provides New Insights into the Growth Superiority of a Novel Grouper Hybrid

Grouper (Epinephelus spp.) is a group of fish species with great economic importance in Asian countries. A novel hybrid grouper, generated by us and called the Hulong grouper (Hyb), has better growth performance than its parents, E. fuscoguttatus (Efu, ♀) and E. lanceolatus (Ela, ♂). We previously reported that the GH/IGF (growth hormone/insulin-like growth factor) system in the brain and liver contributed to the superior growth of the Hyb. In this study, using transcriptome sequencing (RNA-seq) and quantitative real-time PCR (qRT-PCR), we analyzed RNA expression levels of comprehensive genes in the muscle of the hybrid and its parents. Our data showed that genes involved in glycolysis and calcium signaling in addition to troponins are up-regulated in the Hyb. The results suggested that the activity of the upstream GH/IGF system in the brain and liver, along with the up-regulated glycolytic genes as well as ryanodine receptors (RyRs) and troponins related to the calcium signaling pathway in muscle, led to enhanced growth in the hybrid grouper. Muscle contraction inducing growth could be the major contributor to the growth superiority in our novel hybrid grouper, which may be a common mechanism for hybrid superiority in fishes.石斑鱼（Epinephelus spp.）是一类在亚洲国家具有极高经济价值的鱼类类群。本研究团队培育获得一种新型杂交石斑鱼，命名为虎龙杂交石斑鱼（Hulong grouper, Hyb），其生长性能优于其亲本雌性棕点石斑鱼（E. fuscoguttatus, Efu, ♀）与雄性鞍带石斑鱼（E. lanceolatus, Ela, ♂）。我们此前已报道，脑与肝脏中的生长激素/胰岛素样生长因子（GH/IGF）系统是该杂交石斑鱼生长优势的重要贡献因素。本研究通过转录组测序（RNA-seq）与实时荧光定量PCR（qRT-PCR）技术，对杂交石斑鱼及其亲本肌肉组织的全基因RNA表达水平进行了分析。数据结果显示，杂交石斑鱼肌肉中参与糖酵解、钙信号通路的基因以及肌钙蛋白相关基因均呈上调表达。研究表明，脑与肝脏中上游GH/IGF系统的活化，配合肌肉中上调的糖酵解基因、钙信号通路相关的兰尼碱受体（RyRs）与肌钙蛋白，共同促进了杂交石斑鱼的生长性能提升。肌肉收缩诱导生长或是本新型杂交石斑鱼生长优势的核心成因，这一机制可能普遍存在于鱼类的杂交优势现象中。