油棕EST序列中SSR的分布特征分析

为充分利用现有公共数据库中的EST资源开发EST-SSR引物，本研究从GenBank数据库获取39 227条油棕EST，通过聚类拼接和处理，得到全长为7977.734 kb的无冗余序列15 716条。在这些序列中共检索出699个SSRs，检出率为4.45%，平均11.41 kb出现1个SSR，包括99种重复基元。其中，二核苷酸和三核苷酸重复是主要的类型，分别占总SSRs的38.48%和25.32%。在所有的核苷酸重复基序中，二核苷酸重复序列AG/CT所占比例最高，约占27.47%。Blastx分析发现44.95%的SSR-ESTs与非冗余蛋白质序列数据库(nr)中功能基因同源，功能已知的蛋白质中葡萄来源的SSR-ESTs所占比例最大，为4.42%。同时对54条SSR-ESTs通过GO体系进行功能分类，其中46条能找到同源物，其余8条无同源物，这些序列可划分为18个亚类，在所有功能亚类中，结合活性的功能项和SSR-ESTs数量最多，另外580条未被注释功能信息。本结果将为利用EST-SSR标记来研究油棕基因组学和开展分子育种工作提供参考依据。

Analysis of SSR characteristics in EST sequences of oil palm(Elaeis guineensis Jacg.)

In order to make full use of the EST resources in the present public database to develop the EST-SSR primers,in this study,39 227 ESTs of oil palm(Elaeis guineensis Jacg.) from GenBank database were downloaded and analyzed,resulting in 15 716 non-redundant sequences with total length about 7 977.734 kb.699 SSRs were discovered,the frequency of these EST-SSRs was 4.45% and the mean distance was 11.41 kb in non-redundant ESTs.Among them the dinucleotide and trinucleotide repeats were dominant types,accounting for 38.48% and 25.32% respectively.AG/CT was repeated most in all nucleotide repeat motifs,accounting for 27.47%.Blast analysis showed that 44.95% of SSR-ESTs were homologous with functional gene in non-redundant protein sequences databases(Nr database).The homology with known functions from Vitis vinifera had the greatest proportion and reached up to 4.42%.Simultaneously,the functional classification of 54 SSR-ESTs as made by GO system,of which 46 were found in the Nr and EST database,and the other 8 showed no homology.These ESTs can be divided into 18 functional subclasses,and the functional items and SSR-ESTs relevant to binding presented higher quantity than all other functional subclasses.The function of other 580 ESTs was not researched.