【摘要】 ESTs数据库的发展为分子标记的开发提供了宝贵的资源。本研究从NCBI下载与杨树木质部形成相关的5359条ESTs序列,在其中257条序列中检测到279个SSRs位点,检出率为5.2%。全部SSRs共分为84种重复单元,平均长度18.2bp,变幅为15～36bp,平均分布频率1/6.94kb。所有类型中三核苷酸重复单元占总SSRs的41.3%,处于主导地位。AAG占三核苷酸重复单元的比例为27.0%,是三核苷酸重复单元中的优势重复类型。利用primer3在线设计引物,通过生物信息学方法筛选出7对引物,其中6对扩增效果较好。利用筛选出的引物对19个杨树无性系进行扩增,每对引物产生多态性条带数目为3～6条,平均4.16条。引物多态信息量变化范围为0.2267～0.9845,平均0.5485。应用NTSYS软件在相似系数为0.68水平可将19个杨树无性系准确聚类。研究结果表明,利用ESTs序列进行SSRs的开发是一种切实有效的方法,为EST-SSRs在杨树遗传图谱构建以及遗传多样性等方面的应用奠定了基础。更多还原

【Abstract】 Expressed sequence tags(ESTs) data provide valuable resources for development of molecular markers.In present study,we downloaded a total of 5 359 poplar unigene sequences related with xyligenesis from NCBI,and identified 279 SSRs in 257 sequences,accounting for5.2%of the whole EST sequences.Among them,84 SSR motifs were founded.The length of SSRs were changed from 15 bp to 36 bp,with the average length of 18.2 bp and the average distance of 1/6.94 kb.The trinucleotide repeats appeared to be the most abundant SSRs(41.3%).The rich repeats AAG were predominant,accounting for 27.0% in tri-nucleotide repeats.By using primer3,we screened and designed seven primerpair.Six primers were validated as usable markers.These primers revealed moderate to high polymorphism information content.The polymorphic bands that amplified by 6 primers were ranged from 3 to 6,with an average of 4.16.The mean PIC value was 0.548 5,ranging from 0.226 7 to 0.984 5.Nineteen poplar clones were separated into two major clusters by UPGMA analysis at level of 0.68 similarity.These results showed that derive SSRs from ESTs sequence is a realistic and effective approach,which may give insight into EST-SSRs application in poplargenetic map construction and genetic diversity research.更多还原