单环刺螠(Urechis unicinctus)微卫星标记开发及5个地理种群遗传结构分析

MICROSATELLITE MARKER ISOLATION AND GENETIC STRUCTURE ANALYSIS FOR FIVE POPULATIONS OF URECHIS UNICINCTUS

采用高通量测序法从单环刺螠基因组中开发微卫星标记,并通过一个秦皇岛单环刺螠野生群体对其进行多态性评价,利用获得的多态性引物对秦皇岛、烟台、潍坊、青岛、大连5个不同海区的野生单环刺螠群体进行了遗传多样性及遗传结构分析。结果表明:本实验设计的50个微卫星标记能稳定扩增的有38个,其中22个微卫星位点在5个群体中均表现为高多态性,等位基因数(Na)介于24—44之间,多态信息含量(PIC)介于0.921—0.967之间。5个群体总的平均有效等位基因数(N_e)范围为6.629—8.850,平均观测杂合度(Ho)和平均期望杂合度(He)范围分别为0.790—0.912、0.851—0.896,大连群体的杂合度最大(H_e=0.8962),潍坊群体的最小(H_e=0.8510),其中有12个微卫星位点在不同群体中出现显著偏离Hardy-Weinberg平衡的现象。平均遗传分化指数(FST)表明,群体分化水平处于中等分化水平(FST值为0.0880—0.1136);聚类分析显示烟台群体先与青岛群体聚为一支,再与秦皇岛群体聚类,然后跟潍坊群体聚为一支,大连群体单独聚为一支;遗传距离模式(IBD)显示单环刺螠群体的地理距离与遗传距离间不存在显著的线性关系。本研究开发的22对微卫星标记可以用于单环刺螠遗传结构分析研究,为下一步单环刺螠种质资源保护和人工繁育提供参考依据。

Urechis unicinctus is an economically important marine benthos distributed widely in intertidal zone of Yellow Sea and Bohai Sea. To sustain the resources that have been reduced dramatically in recent years, understanding the genetic diversity and population structure of wild stocks for breeding, we isolated the microsatellite markers by high-throughput sequencing for the species sampled from 5 natural populations in Qinhuangdao（QHD）, Yantai（YT）, Weifang（WF）, Qingdao（QD）, and Dalian（DL）. Among 50 pairs of microsatellite primers we designed, 38 presented obvious bands. Moreover, 22 loci showed high polymorphism, the allele number（Na） of these loci ranged 24—44, the polymorphism information contention（PIC） 0.921—0.967, and the effective allele number（Ne） 6.629—8.850. The average observed（Ho） and expected heterozygosity（He） were 0.790—0.912 and 0.851—0.896, respectively. The maximum He（0.8962） was found in DL population and the minimum（0.8510） in WF population. Nine out of the 22 loci showed deviations from Hardy-Weinberg equilibrium in different population. The average genetic differentiation（FST） ranged 0.0880 to 0.1136, suggesting that the population differentiation was at the middle level. In UPGMA phylogenetic tree, YT and QD populations clustered first, then QHD population jointed, and lastly WF and DL populations. As shown in IBD analysis, no significant linear relationship was revealed between geographical and genetic distances in these populations. These microsatellite markers can help us to analyze the population genetic structure and provide reference for artificial breeding and germplasm resources protection for U. unicinctus in the future.