亚历山大藻属微卫星标记的筛选

Screening of microsatellite markers in Alexandrium spp.

采用生物信息学方法,从塔玛亚历山大藻的ESTs数据库中筛选微卫星(Simple Sequence Repeat,SSR)位点,设计SSR引物,利用毛细管电泳对4株塔玛亚历山大藻(Alexandrium tamarense)、2株相关亚历山大藻(Alexandrium affine)和1株链状亚历山大藻(Alexandrium catenella)进行种内、种间遗传多样性分析,获得以下主要结果:(1)从6830条非冗余的ESTs中共查找到222个SSR,平均每18.5kb就有一个SSR,三核苷酸重复在所有的重复类型中所占比例最大,达到48.2%,重复单元CTG/CAG出现频率最高。进一步筛选出12条SSR引物,用于遗传多样性分析。(2)种内遗传多样性水平整体偏低,多态性引物比率仅为41.67%,Nei’s基因多样性平均为0.2130。种间遗传多样性水平较高,多态性引物比率为75%,Nei’s基因多样性平均水平为0.4643;另外,种间遗传分化系数较高,平均水平为0.7051。(3)对7个样品的聚类图分析发现,A.tamarenseCCMP116与A.affineCCMP112遗传距离极为接近;A.tamarenseATHK9301、CCMP1598和ATDH01相互聚在一起;A.catenellaACDH01与A.tamarense分属两枝。以上结果表明,SSR标记在亚历山大藻种内遗传多样性分析方面是一种非常有用的工具。

To provide more information on the molecular identification methods for the genus Alexanderium,some SSR were screened from ESTs database about Alexandrium tamarense by means of bioinformatics.The genetic diversity was analyzed among 4 strains of A.tamarense,2 strains of A.affine and 1 strain of A.catenella by capillary electrophoresis.Totally 222 SSR were discovered,one SSR per 18.5 kb in average.The trinucleotide repeats accounting for 48.2%,were dominant among the repeat motifs,of which CTG/CAG was the most type.Twelve of primers were further screened for the analysis of genetic diversity.Low level of genetic diversity was observed in intraspecies of Alexandrium spp.,with the ratio of polymorphic primers of 41.67% and Nei＇s gene diversity of 0.2130 in average.In contrast,higher genetic diversity was observed in interspecies of Alexandrium spp.with ratio of polymorphic primers of 75% and Nei＇s gene diversity of 0.4643.The interspecies genetic coefficient of differentiation was higher with the average level of 0.7051.According to the dendrogram of these seven strains,A.tamarense CCMP116 and A.affine CCMP112 greatly closed to each other.A.tamarense ATHK9301,CCMP1598 and ATDH01 clustered together.A.catenella ACDH01 and A.tamarense distributed in the two branches.These results suggested that the SSR marker was a potentially useful method in the study of within-species genetic variability of Alexanderium spp.