【摘要】 利用已经公布的粗糙脉孢菌基因组测序结果,对该真菌基因组中的微卫星(SSR)序列进行了系统分析。结果表明,在已经公布的38.0　Mb 的基因组序列中,共有14 788 个以1～6个核苷酸为基序的 SSR序列(长度大于15　bp,匹配值大于80%),其碱基总数占整个基因组碱基数的 0.95%,平均2.57　kb 就分布有一个大于15　bp的SSR。其中数量最多的三碱基 SSR,数量达到 4 729个,其次为六碱基 SSR　(2 940个)和单碱基 SSR(2 489 个),这3 类SSR 总数达10 158 个,占 SSR总数的68.7%。数量最少的是二碱基SSR,只有691 个。在可读框(ORF)中的SSR总数为 4 094个,共分布于2 373个 ORF中,其中只有1 个SSR 的ORF为 1 056个。与其它生物内 SSR的分布类似,在基因编码区中,以三碱基SSR和六碱基SSR占绝对优势,分别为基因组中三碱基和六碱基SSR总数的54.1%和48.8%,由于ORFs和编码区的碱基总数分别为该菌基因组碱基总数的约46%和38.3%,　所以这两种长度的SSR在编码区中的密度高于基因组中的平均密度。ORF上下游300　bp调控区域内是各类SSR相对的富集区。尤其是上游区域中的五碱基SSR,为平均密度的3倍,二碱基SSR和四碱基SSR的密度也是基因组中平均密度的2倍多。在下游调控序列中,五碱基、四碱基、二碱基、单碱基 SSR的密度,也大大超过了在基因?更多还原

【Abstract】 A total of 38.0 Mb of publicly available DNA sequence in Neurospora crassa was researched for mono- to hexanucleotide simple sequence repeat (SSR or microsatellite) to determine the type, size and frequency. A total of 14 788 SSRs were observed in the whole genomic DNA sequence, about one every 2.57 kb, with the criteria of SSR length >15 bp and 80% matches. The most abundant microsatellite were trinucleotide repeat, the number was 4 729, followed by hexanucleotide and mononucleotide repeats, the numbers were 2 940 and 2 489 respectively, and the least abundance was dinucleotide repeat, only 691 were found. Among the 10 082 ORFs, 4 094 SSRs were harbored in 2 373 ORFs no intron) ( of the organism. Onethousand and fifty six ORFs kept only one SSR. Similar with other organisms, tri- and hexanucleotide repeats were predominant in ORFs, 54.1% and 48.8% of tri- and hexanucleotide repeats were distributed in ORF region. The density of these two motifs was overpresented in coding regions, because ORF region and coding region constitutes only 46% and 38.3% of genomic sequence respectively. Upstream and downstream 300 bp of regulatory regions were high density regions of SSRs, particularly density of pentanucleotide SSR in upstream region was as high asfive times of average density in genomic DNA, density of di- and tetranucleotide SSR was also more than two times of average density. The density of penta-, tetra-, di- and mononucleotide SSRs was relatively higher than average density, also. There were 47 SSRs in mitochondria 64 840 bp DNA sequence, their distribution is similar with genomic DNA sequence. These results suggested that SSRs were clustered in regulatory regions of genomic DNA.更多还原