有尾噬菌体目中微卫星和复合型微卫星的发生及分析(英文)

Occurrence and Analysis of Microsatellites and Compound Microsatellites in Caudovirales

简单重复序列亦称微卫星,被成功应用于许多真核生物、原核生物和病毒的基因组和进化研究,但是噬菌体中的微卫星目前很少被研究。因此对60条尾病毒目基因组中的微卫星和和复合型微卫星(由两个或两个以上直接相邻的微卫星组成)做综合性分析,在这60个基因组中总共观察到11 874个微卫星和449个复合型微卫星。相关性分析表明微卫星个数与基因组大小成正线性相关(ρ=0.899,P<0.01)。参考序列中的微卫星个数少于对应的随机序列中微卫星个数,这种反常现象主要是因为参考序列含有较少的单核苷酸和二核苷酸重复。A/T和AT/TA重复是单核苷酸和二核苷酸重复中最主要的类型,因此单核苷酸重复中的GC含量明显低于相应的序列中的GC含量;相比之下,微卫星中的二核苷酸和三核苷酸重复的GC含量与对应的参考序列的GC含量无明显区别。尾病毒目基因组中的这些结果与其它生物体基因组存在一定的差别。有助于了解尾病毒目中微卫星的分布、进化和生物学功能。

Simple sequence repeats （SSRs） or microsatellites have been successfully used for various genetic and evolutionary studies in eukaryotic, prokaryotic and viral systems, but information regarding SSRs in bacteriophages is limited by lack of studies. We made a comprehensive analysis of microsatellites and compound microsatellites （composed of two or more microsatellites residing directly adjacent to each other ） in 60 Caudovirales genomes, and a total of 11 874 microsatellites and 449 compound microsatellites were observed in these genomes. In general, the count of SSRs is proportional to genome size by Pearson linear correlation analysis （p =0. 899,P 〈0.01 ）. Microsatellites in reference sequences are lower than that in random sequences, and it was beyond our expectation. The primarily reason was that reference sequences contain fewer mononucleotide and dinucleotide repeats. A/T and AT/TA were predominant in mononucleotide and dinucleotide repeats in most sequences, so GC content in mononucleotide repeats was notably lower than that in corresponding genome; by contrast, GC content has no significant difference between reference sequences and microsatellites of dinucletide and trinucleotide repeats. These results in Caudovirales are more or less different from other organisms＇ genomes. Our study might be helpful in understanding the distribution, evolution and biological function of microsatellites in Caudovirales.