禾谷镰刀菌和稻瘟病菌基因组中的微卫星序列比较

Comparison of microsatellites in the genome of two phytopathogenic fungi,Fusarium graminearum and Magnaporthe grisea

利用禾谷镰刀菌 Fusarium graminearum 和稻瘟病菌 Magnaporthe grisea 基因组测序结果,对这两种植物病原真菌基因组中的微卫星(SSR)序列进行了系统地分析和比较。结果表明,在禾谷镰刀菌基因组中,共发现4679个 SSR 序列,总长度为96.2 kb,占基因组全长的0.27%。平均7.7kb 碱基中有一个大于15 bp 的 SSR 序列。在稻瘟病菌基因组中共发现16398个 SSR 系列,其总长度达到330 kb,约占整个基因全长的0.85%,平均2.36 kb 碱基中就分布有1个 SSR 序列。在禾谷镰刀菌基因组中,数量最多的是五碱基重复序列,其次是六碱基重复序列;稻瘟病菌基因组中数量最多的是单碱基重复序列,其次为三碱基重复序列和五碱基重复序列。两基因组中数量最少的都是二碱基重复序列。尽管这两种植物病原真菌都属子囊菌,基因组大小也十分接近,但无论是在SSR 的总体数量上,还是在各类 SSR 的分布上,两种植物病原真菌都存在十分显著的差别。

A total of 38.76 Mb of publicly available DNA sequence in two phytopathogens, Fusarium graminearum, Magnaporthe grisea were searched for mono- to hexanucleotide simple sequence repeat （SSR or microsatellite） to determine the type, size and frequency. A total of 4679 SSRs were observed in genomic DNA with criteria of SSR length 〉 15 bp and 80% matches. Total length of SSRs is 96.2kb, constituting 0.27% of genomic DNA in F. graminearum. While 16398 SSRs were observed in genomic DNA sequence in M. grisea with the same criteria. The average density is one SSRs every 7.7 kb in genomic sequence in F. graminearum and every 2.36 kb in genomic DNA of M. grisea. The most abundance microsatellite is pentanucleotide SSR, following by hexanucleotide SSR in F. graminearum; while mono- and trinucleotide SSR were the most frequent repeat in M. grisea. The least SSRs were dinucleotide repeats in both. These results showed that two phytopathogenic fungi exhibit quite different preferences for SSR type and distribution, and overall microsatellite number, though both belong to ascomycetes, genome size were very similar.