基于全基因组重测序的大口黑鲈养殖群体的遗传多样性和选择消除分析

Genetic diversity and selection elimination analyses of farmed Micropterus salmoides populations by the whole-genome resequencing

  • 摘要:
    目的 为了实现我国重要淡水养殖品种——大口黑鲈养殖的可持续发展, 建立一种长期、有效的、且低成本的监测养殖群体遗传多样的方法,我们基于二代高通量测序技术,对大口黑鲈群体进行低深度基因组重测序,鉴定养殖群体的遗传变异,评估群体遗传多样性,以并通过群体遗传学的研究发现了不同环境下养殖群体染色体受到选择的区域,以探求环境对基因组变异的影响,为后续分子生物学的研究打下基础。
    方法 本研究采用第二代高通量测序技术,对来自江苏、安徽、浙江、广东的7个养殖群体的共55个个体进行了平均测序深度为5-10×的基因组重测序,对鉴定出的多态性信息位点进行群体遗传多样性、群体结构和选择消除分析。重测序后共得到2 675 780 690条reads,与参考基因组比对后,共鉴定出2 550 187个单核苷酸多样性(SNP)位点。
    结果 系统进化关系和种群遗传结构结果显示,这7个群体可能来自于两个种源,而肇庆、苏州、泰州、金华群体都是离祖先群体亲缘关系较近的群体,我们推测,这些群体可能随着人工养殖而流向湖州、徐州和六安。基于遗传多样性结果可以发现,最靠近祖先群体的肇庆,遗传多样性最低。通过肇庆与徐州、湖州和六安3个对照群体分别进行的基于群体分化指数(Fst)和核苷酸多态性(Pi)选择消除分析,发现主要在1号和18号染色体上存在强烈的受选择信号。在这些区域中,共发现16个与生长和免疫相关的基因。群体结构分析和遗传多样性指数结果都提示,这些养殖群体可能来自2个种源。目前,养殖群体内的遗传多样性较低,大部分群体的多态信息含量(PIC)值低于0.25,面临种质退化的风险。这些群体中,肇庆群体的遗传多样性最低。
    结论 本研究对国内养殖大口黑鲈遗传多样性状况进行的统计和分析,为大口黑鲈养殖育种和养殖提供了有价值的参考数据。

     

    Abstract: Micropterus salmoides, commonly known as largemouth bass, was introduced to mainland China (Guangdong Province) in 1983. Due to long-term artificial breeding and inbreeding, its germplasm has degraded, making it necessary to monitor its genetic diversity. In order to realize the sustainable development of aquaculture, we try to develop a long-term, effective, and low-cost method for monitoring the genetic diversity of the breeding population in M.salmoides, an important freshwater breeding species in China. We applied a low-depth (10×) second-generation high-throughput technology to the genome resequencing of 55 individuals from 7 farmed populations respectively collected in Jiangsu, Anhui, Zhejiang, and Guangdong province. A total of 2 675 780 690 reads were generated in the resequencing, which identified 2 550,187 single nucleotide diversity (SNP) loci when they were compared with the reference genome. The constructed phylogenetic relationship and population structure indicated that the 7 populations probably originated from two provenances and the Zhaoqing, Suzhou, Taizhou and Jinhua populations were closer relationship to the provenances. We speculated that these 4 populations might migrate to Huzhou, Xuzhou and Lu 'an with the following artificial cultivation. It was observed that the Zhaoqing pupulation, closest to the ancestral population, had the lowest genetic diversity. Analyses of population structure and genetic diversity indexes also agreed with that these cultured populations derived from two provenances. The selection elimination analysis by the calculation of population differentiation index (Fst) and nucleotide diversity (Pi) compared Zhaoqing and each of another 3 control populations, Xuzhou, Huzhou or Lu 'an control populations, respectively, which detected strong selective signals on chromosomes 1 and 18 of Zhaoqing where 16 genes were localized. These genes were annotated to be involved in growth and immunity. The identified low genetic diversity (PIC less than 0.25) in most of the cultured populations reflected the risk of germplasm degradation. The data outputs will lay a foundation for molecular biology research in M. salmoides by providing fundamental reference data for the breeding.

     

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