目的:利用磁珠富集法构建霍山石斛的微卫星文库,用筛选出的微卫星引物对安徽霍山居群的24株野生霍山石斛进行遗传多样性分析.方法:根据链亲和素磁珠和生物素特异结合的特性,用3'端生物素标记的探针与两端连接已知序列人工接头的霍山石斛基因组DNA酶切片段杂交,杂交复合物结合到包被有链亲和素的磁珠上,洗脱并收集吸附在磁珠上的含有微卫星的片段.经过克隆和测序,再根据微卫星两侧的保守序列设计引物,最后利用从中筛选出的微卫星引物对霍山石斛居群进行遗传学分析.结果:本实验共筛选得到12对多态性位点丰富、带型清晰、重复性好的引物,并检测到65个等位基因,每个位点的等位基因数从2到8个不等,平均预期杂合度(HE)和平均观察杂合度(HO)分别为0.638,0.500.12个多态性位点的哈温平衡检测结果显示有2个位点显著偏离哈温平衡(P<0.05),可能是由于存在无效等位基因.连锁不平衡检测结果表明有3对位点显著连锁不平衡(P<0.05);结论:这些微卫星标记可以用于霍山石斛的居群遗传学分析.
Objective: To investigate the genetic diversity and structure of Dendrobium huoshanense, a (CT)n enriched microsatellite library was constructed using a magnetic beads enrichment procedure. Method: The 3''-biotinylated oligonucleotide probe was used to hybridize with the digested D. huoshanense genomic DNA fragments whose both ends were ligated with adaptors. The hybridized complex was then combined with the streptavidin-coated magnetic beads. The captured microsatellite fragments were eluted, collected and cloned into pMD19-T vector. The recombinant plasmids were transformed into Escherichia coli DH5α competent cells. The clones that yielded two or more bands contained microsatellite fractions. Positive clones were screened and sequenced. Thirty pairs of primers were designed and synthesized. Polymorphism at each locus was determined using 24 individuals from a natural population from Huoshan county town in Anhui province. Result: Twelve polymorphic microsatellite loci from the microsatellite-enriched genomic library were newly developed across 24 D. huoshanense individuals. In total, 65 alleles were identified, and the number of alleles per locus ranged from 2 to 8. The mean observed and expected heterozygosities were 0.500 and 0.638, respectively. Two loci significantly deviated from Hardy-Weinberg equilibrium (P<0.05), which could be due to the presence of null alleles. Furthermore, three of twelve loci showed significant linkage disequilibrium (P<0.05). Conclusion: These results suggest that the identified polymorphic microsatellite markers will be useful in population genetic studies of D. huoshanense.