【作者】 阎毛毛； 戴晓港； 李淑娴； 尹佟明；

【Author】 YAN Mao-Mao~1,DAI Xiao-Gang~1,Li Shu-Xian~1,YIN Tong-Ming~2 (Jiangsu Key Laboratory Poplar Germplasm Enhancement and Variety Improvement,Nanjing Forestry University,Nanjing 210037,China)

【机构】 江苏省杨树品种改良与种质创新重点实验室南京林业大学；

【摘要】 微卫星是生物基因组中变异频率最快的序列,结构基因中微卫星重复数的变化会引起基因的框移突变,因此在进化过程中,基因区微卫星会受到强烈选择的影响。在本研究中,分析了松树、杨树及桉树基因组的EST(Express sequence tag,表达序列标签)序列各三万条。分析结果显示,桉树和杨树EST序列含有微卫星的比例比较接近,分别为18.7%和15.3%,而在松树中则发生了较大分化,只有8.2%。研究发现,三碱基重复单元是这三个树种编码序列中微卫星的主要重复类型。除三碱基重复微卫星外,桉树和杨树EST序列中其它类型微卫星的丰度随着重复单元长度的增加而减少,而在松树中则呈相反现象。同时值得注意的是松树EST序列中变异频率快的微卫星(>20bp)数量明显比桉树及杨树少。研究还发现,三个树种中微卫星获得或丢失重复单元的速率都随着重复单元的增加而降低。更多还原

【Abstract】 Microsatellites are the most variable sequences in the genome of different organisms. Changes in repeat motif numbers will lead to frameshift mutation of the corresponding genes.During the evolutionary time,microsatellites in transcribed sequences have undergone strong selection.In this study,thirty thousand ESTs were analyzed for pine,poplar and eucalyptus respectively.The results showed that the percentage of ESTs containing SSRs was similar in eucalyptus and poplars,accounting for 18.71%and 15.33% respectively.By contrast,this ratio was significantly lower in pine,only accounting for 8.22%.A common phenomenon observed in the three tree species was that the triplet repeats were the dominant microsatellites in the investigated EST sequences.Except for the triplet SSRs,richness of different type SSRs decreased with increase of repeat motif lengths in eucalyptus and poplars,but an opposite trend was observed in pine.It was noteworthy that content of highly polymorphic microsatellites(>20bp) was higher in ESTs of eucalyptus and poplars than that of pine.The results also showed that,in these three tree species,the frequency of microsatellite gained or lost repeat unit/units decreased with increase in the repeat motif lengths of different types of microsatellites.更多还原