鳙大、小个体比较转录组及差异表达基因与体重的关联性研究

Fast growth is a highly important trait for aquaculture fish, However, up today,comprehensive information about genes involving in modulation of fast and slow growth remains rare in fish. Rapid development of highthrouphput nex-generation sequencing technologies allows us to ientify huge amounts of genes that may determine extreme growth traits in transcriptomes of fish. In this study, hypothalamic-pituitary and liver tissues of large size and small size bighead carp (Hypophthalmichthys nobilis) individuals from the same family and population, were used to perform RNA-seq,and comparative transcriptome analyses were applied to elucidate the whole transcripts of somatropic axis especially neuro-endocrine system and differentially expressed genes. Meanwhile,top 50 differentially expressed genes will be selected as the most important target to perform qPCR expression analysis, genetic association studies including candidate gene association analysis and LD (linkage disequilibrium)-based association analysis (or association mapping) for growth (body weight) trait and those 50 genes and their SSR （microsatellite）amd SNP (single nucleotide polymorphism) markers. The aims of this study are to identify a large amount of key genes in neuro-endocrine system involving in genetic modulation of growth rate in bighead carp, amd also to perform functional validation and association analyses for body weight and selected genes at family and population level. This study will provide valuable information and insights into the elucidation of genetic machanism for fast growth in fish, and also novel candidate genes or major genes and their molecular markers with practical values for the studies on molecular breeding in bighead carp. The results of this study will be also important for basic studies of fish genetics and breeding with theoretical and applied significance in economic fishes particularly those in Cyprinidae.

快速生长是鱼类的重要经济性状，但调控鱼类生长速率的完整基因信息仍很缺乏。高通量测序技术使得在转录组水平上发掘与鱼类极端生长性状调控有关的海量基因成为可能。本研究拟以鳙家系和群体中极大和极小个体的下丘脑-垂体和肝脏为材料进行RNA-seq分析，以比较转录组方法揭示鳙极端生长差异有关的生长轴尤其神经内分泌系统的全部转录本及差异表达基因；同时拟以表达差异较大的50个基因为重点，开展基因表达量(qPCR)以及基因分子标记与体重的候选基因关联性和基于LD（linkage disequilibrium）的关联性分析。本项目的目标是发掘与鳙生长速率调控有关的一批关键基因，并在群体和家系水平进行基因-体重关系的功能性验证。本项目将为解析鱼类快速生长的分子遗传机制提供新线索，也将为鳙生长的分子育种研究提供具有实用价值的候选基因或主效基因及其分子标记。相关结果对鲤科经济鱼类遗传学和育种学基础研究具有重要意义。

调控鱼类生长速率的完整基因信息仍很缺乏，RNA-seq等高通量测序技术使得在转录组水平上发掘与鱼类极端生长性状调控有关的海量基因成为可能。基于转录组产生的差异表达基因等信息，筛查基因内的单核苷酸变异并探讨其与生长性状的关联性，是转录组信息应用于鱼类遗传学和分子标记辅助育种的可能途径之一。 本研究通过对鳙家系和群体中极大和极小个体的下丘脑-垂体（HP）和肝脏（liver）组织样本的RNA-seq分析，以比较转录组方法揭示鳙极端生长差异有关的生长轴尤其神经内分泌系统的转录本和差异表达基因信息；以表达差异较大的基因和其他QTL相关候选基因为重点，开展基因表达量(qPCR)以及基因分子标记与体重的候选基因关联性析。本项目的转录组测序获得了高体重组和低体重组下丘脑-垂体和肝脏平均25M/样品 clean reads，比对到鳙基因组组装数据的比例平均为93.09%和92.25%；高、低体重组之间的差异表达基因共378个，在高体重组上调表达的基因有163个；比较转录组分析得到的基因表达水平与qPCR验证结果基本一致。 基于差异表达较大的50个基因和生长QTL相关的其它候选基因，我们共发掘了161个SNP标记，关联分析后得到32个与鳙体重等性状显著关联的SNP位点（P<0.05）。 基于FST等基因的28个生长显著相关SNP标记池，大规模筛选鳙子代基因型的结果表明，SNP优势基因型聚合的数量与体重等生长性状的优劣呈正相关。本项目基于转录组信息发掘获得了与鳙生长速率调控有关的一批重要候选基因，并在群体和家系水平进行基因-体重关系的功能性验证，为解析大宗经济鱼类快速生长的分子遗传机制提供了新线索，也为鳙后备亲本筛选等生长相关的分子标记辅助育种研究提供了具有实用价值的候选基因及其SNP标记资源。这类研究结果对其他鲤科经济鱼类的遗传学和育种学基础研究也具有较好参加价值。