人参单一基因微卫星标记的分析

 【目的】利用人参单一基因（unigene）序列，研究人参转录区SSR的分布特征；开发单一基因微卫星（UGMS）标记，并比较人参UGMS与基因组SSR标记（G-SSR）在分布频率、多态性及通用性等方面的不同，为人参等五加科药用植物的鉴定、遗传图谱的建立等研究奠定基础。【方法】利用NCBI公共数据库的7 649条人参EST序列，筛选出含有SSR的单一基因序列，并分析人参SSR的分布；根据这些序列以及包含SSR的人参基因组序列合成的引物扩增人参不同品种和其它五加科植物。【结果】检测到总长度为2.72 Mb的4 869个单一基因。其中，488个单一基因分布有724个SSR，占人参EST的10.02%，SSR的分布密度为3.75 Kb。一至三核苷酸重复分布频率分别为29.28%、48.06%和19.06%。非编码区和编码区重复序列分别以AT/TA和AAG/CTT为主。在合成的100对UGMS和44对G-SSR引物中，分别有86和44对能够扩增出人参的PCR产物，其多态率分别为42.0%和43.2%。人参UGMS对五加科西洋参、三七和刺五加植物的通用性分别为100%、87.2%和75.6%；G-SSR分别为95.5%、72.7%和40.9%。【结论】人参基因中SSR发生频率较高，并以二核苷酸重复为主。不同基因区域内的SSR分布具有非随机性。UGMS在揭示种内多态性方面不及G-SSR，但具有较高的种间通用性。

Development of Unigene Derived Microsatellite (UGMS) Markers in Panax ginseng

  【Objective】The aims of this study is to characterize the distribution of simple sequence repeats (SSR) in the transcribed regions of Panax ginseng, and to develop genomic SSR (G-SSR) and unigene derived microsatellite (UGMS) markers in Panax ginseng. 【Method】A data set of 7 649 expressed sequence tags (ESTs) of P. ginseng downloaded from NCBI was assembled to obtain the unigenes. SSR-containing unigenes and genome were selected to characterize the SSR distribution in ginseng genome. A set of UGMS and G-SSR primers was designed to amplify genomic DNA of ginseng and other Araliaceae species. 【Result】A total of 4 869 unigenes with a length of 2.72 Mb were predicted. From 488 SSR-containing unigenes (10.02%), 724 UGMS were identified with a density of 1 per 3.75 kb of unigenes. Dinucleotide repeats (48.06%) were the most abundant followed by mono (29.28%) and tri-nucleotide repeats (19.06%). The motifs of AT/TA and AAG/CTT were mostly distributed in untranslated region and protein coding region, respectively. Among the 100 UGMS and 44 G-SSR primer pairs, 86 and 44 ones showed amplifications in a set of 9 ginseng accessions. Polymorphisms between the accessions were found to be 42.0% and 43.2%, respectively. The transferability of ginseng UGMS marker to P. guinquefolius, P. notoginseg and E. senticosus was 100%, 87.2% and 75.6%, while 95.5%, 72.7% and 40.9% for G-SSR, respectively. 【Conclusion】The SSR shows higher frequency in ginseng and the most abundant motif is dinucleotide. The distribution of UGMS was non-random with respect to different genic regions. UGMS markers detected a lower polymorphism but a higher level of transferability than those derived from genomic SSR.