虾夷扇贝自交家系近交衰退效应的遗传调控机制分析

Japanese scallop is one of the most important maricultural shellfish in the north of China. In recent years, with the increasing acreage for artificial farming, its cultured stocks have been frequently showing signs of inbreeding depression, which hampers the healthy and sustainable development of scallop aquaculture. In this study, by using the selfing lines of Japanese scallop as the research model, we aim to investigate the genetic mechanism of scallop inbreeding depression from both genomic and transcriptomic levels. The research plan includes: First, by using the high-throughput and cost-effective SNP genotyping technique, genetic loci that contribute the inbreeding depression are searched and determined through linkage and vQTL analyses of several selfing lines; Second, by using the high-throughput transcriptome sequencing technique, candidate genes and their associated regulatory networks that are involved in the inbreeding depression are identified through coding-region marker segregation and gene coexpression network analyses, and are subsequently linked with genetic loci by eQTL analysis; Finally, results from vQTL, eQTL and gene network are integrated together to determine and functionally validate the key genes and their associated regulatory networks responsible for inbreeding depression. This study will not only lay an important foundation for further investigations of shellfish inbreeding depression, but also demonstrate that scallop selfing lines are an excellent research model for studying shellfish inbreeding depression. Our study would provide necessary technical and theoretical support for further genetic improvement of Japanese scallops.

虾夷扇贝是我国北方最重要的海水养殖贝类之一。近些年来，随着养殖规模的不断扩大，虾夷扇贝养殖群体逐渐出现一定程度的近交衰退现象，严重影响了虾夷扇贝养殖业的健康、可持续发展。本研究以虾夷扇贝自交系作为研究模型，从基因组、转录组水平上研究其近交衰退的遗传机制。主要研究内容包括：利用高通量低成本SNP分型技术，对虾夷扇贝多个自交系进行连锁及vQTL分析，筛查和确定控制近交衰退的遗传决定位点及其作用方式；利用高通量基因表达谱测序技术，通过对基因区标记分离分析及基因共表达网络分析，筛查与近交衰退相关的重要基因模块及其网络调控基因，并对其进行eQTL定位；将vQTL、eQTL及基因网络等多种分析方法相结合，鉴别控制虾夷扇贝近交衰退的关键调控基因，研究其调控机制并进行功能验证。本项目的研究成果将为海洋贝类近交衰退领域的理论研究提供基础资料和新的模型生物，为培育高产、抗逆的虾夷扇贝新品种提供技术和理论支持。

本课题目前已达到既定的研究目标，取得了预期的研究成果。通过表型性状、基因组、转录组等多个水平上全面解析了虾夷扇贝近交衰退产生的分子基础及遗传调控机制。阐明了不同近交系数下不同性状的衰退特点，揭示了生长性状和存活性状受到不同位点、不同方式的调控作用。从全基因组角度发现了大量偏分离标记，通过偏分离标记类型的分析，证实了在虾夷扇贝近交衰退中显性效应和超显性效应都起作用且作用相当。从转录组角度发现了基因表达水平的变异是造成生长衰退的主要原因，体现在EGF基因家族的整体下调。而存活率的衰退，可能是由蛋白功能的变异引起的，表明两类性状衰退的分子机理不同。通过连锁图谱定位的偏分离QTL区域及表达差异的eQTL区域的基因功能分析，鉴别到近交衰退相关的网络调控基因，并对其调控模式进行了初步解析。基于本研究的结果充分显示了虾夷扇贝自交家系是研究海洋贝类近交效应的理想动物模型，本项目的研究成果为海洋贝类近交领域的理论研究提供了系统的研究思路和新的模型生物。在近交衰退方面取得的研究成果，将有助于合理利用近交或自交加速育种进程，有效避免近交对产业造成的影响危害，为培育高产、抗逆、优质的海产养殖动物新品种提供技术和理论支持。共计发表论文 3篇，正在投稿论文1篇，获得国家授权专利1项。