罗非鱼chrLG18号染色体耐盐性状主效QTL区间内候选基因鉴定及其功能机制研究

渗透压调节与鱼类生命活动密切相关。目前鱼类渗透压调节机制仍不清晰，影响了耐盐优质鱼类新品系分子选育的效率。我们团队以南方主养的罗非鱼为研究对象，首次在其基因组chrLG18号染色体上鉴定了一个品系间相对保守的耐盐性状主效QTL区间。该区间内多个高盐逆境响应基因呈串联排列，但区间内并未发现已知保守的一些重要渗透压调节基因，结果揭示该区间内可能存在未知的重要基因参与了罗非鱼渗透压分子调控。在此研究基础上，本项目拟综合应用GWAS技术、Hi-C技术及分子生物学手段，重点开展三个方面的工作：1.解析罗非鱼chrLG18号染色体耐盐性状QTL区间内重要调节基因的基因组精细位置及其关键突变位点；2.阐明这些基因参与罗非鱼渗透压调节的分子机制；3.评价重要候选基因在耐盐优质罗非鱼分子选育中的应用前景。项目获得的成果将有助于了解鱼类渗透压调节机制，并为培育优质耐盐罗非鱼新品系提供重要标记和基因资源。

Osmoregulation plays critically important roles in fish facing environmental salinity stress. In spite of the importance of osmoregulation, surprisingly little is known about how fish deals with physiological problems inherent in living in hypo-osmotic and hyperosmotic environments yet. The underlying osmoregulatory mechanisms in fishes are still unclear. Mapping QTL and finding functional genes and linked markers for salt tolerant traits will speed up the improvement of the salt tolerance and other economic traits in fish breeding and help following identification of responsible genes to clarify the molecular mechanism involving into osmoregulation...Tilapias are agriculturally and economically important aquatic fish worldwide. Tilapia are also important candidate species for brackish water aquaculture. In recent, we detected a major QTL peak at the 23 Mb of chrLG18 in Nile tilapia by QTL-seq and GWAS analysis. A long conserved QTL cluster across chrLG18 controlling for the salt tolerant trait was identified for red tilapia and Nile tilapia by using QTL-seq. More than 10 candidate genes near or within the QTL interval have been identified significantly differentially expressed under different salinity challenges. However, function for most of the genes was still unknown. Surprisingly, some important osmoregulation genes, such as PRL1, PRL2, PRLR, Na+/K+ ATPase and Glucocorticoid receptors were not found in the major QTL. These suggested that osmoregulation were more complicated than expected. Further study may disclose novel genes or networks acting in osmoregulation in tilapia...In this proposal, by using integrated methods including GWAS, Hi-C and molecular technologies, we are planning to 1. dissect the fine positions of candidate genes and their functional mutation sites within the QTL region of the chromosome chrLG18 in tilapia, 2. clarify the underlying osmoregulatory mechanisms for these candidate genes in tilapia, 3. evaluate the application of the candidate genes and linked makers in selection of elite tilapia with salt tolerance by using molecular breeding. Our data may provide novel knowledge of osmoregulatory mechanisms in fishes and supply a basis for selection of elite lines with salt tolerance in tilapia.