siRNA-dependent and -independent post-transcriptional cosuppression of the LTR-retrotransposon MAGGY in the phytopathogenic fungus Magnaporthe oryzae.
siRNA-dependent and -independent post-transcriptional cosuppression of the LTR-retrotransposon MAGGY in the phytopathogenic fungus Magnaporthe oryzae.
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DOI：
10.1093/nar/gkm646
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发表时间：
2007
影响因子：
14.9
通讯作者：
Nakayashiki H
中科院分区：
文献类型：
--
作者：
Murata T;Kadotani N;Yamaguchi M;Tosa Y;Mayama S;Nakayashiki H
将LTR-反转录转座子Maggy导入不同遗传背景的稻瘟菌幼稚基因组(野生型、MoDcl1[mdl1]和MoDcl2[mdl2]Dicer突变体)。缺少Maggy siRNA生物发生的MoDcl2突变体通常表现出比野生型和正常Maggy siRNA积累的MoDcl2突变体更大的Maggy mRNA积累和更快的Maggy拷贝数增加，这表明RNA沉默对入侵元件具有有效的防御作用。然而，有趣的是，无论遗传背景如何，Maggy转座的速度随着其在基因组中的拷贝数的增加而急剧下降。值得注意的是，在MoDcl2突变体中，拷贝数依赖的Maggy抑制没有减少其mRNA的积累，因此通过一种不同于转录基因沉默和siRNA介导的RNA沉默的沉默机制。这可能意味着某些机制可能类似于酿酒酵母中Ty1逆转录转座的转录后共抑制，其作用与靶转录物的丰度无关，与RNA沉默无关，在拥有RNA沉默机制的米曲霉中也发挥作用。
The LTR-retrotransposon MAGGY was introduced into naive genomes of Magnaporthe oryzae with different genetic backgrounds (wild-type, and MoDcl1 [mdl1] and MoDcl2 [mdl2] dicer mutants). The MoDcl2 mutants deficient in MAGGY siRNA biogenesis generally showed greater MAGGY mRNA accumulation and more rapid increase in MAGGY copy number than did the wild-type and MoDcl1 mutants exhibiting normal MAGGY siRNA accumulation, indicating that RNA silencing functioned as an effective defense against the invading element. Interestingly, however, regardless of genetic background, the rate of MAGGY transposition drastically decreased as its copy number in the genome increased. Notably, in the MoDcl2 mutant, copy-number-dependent MAGGY suppression occurred without a reduction in its mRNA accumulation, and therefore by a silencing mechanism distinct from both transcriptional gene silencing and siRNA-mediated RNA silencing. This might imply that some mechanism possibly similar to post-transcriptional cosuppression of Ty1 retrotransposition in Saccharomyces cerevisiae, which operates regardless of the abundance of target transcript and independent of RNA silencing, would also function in M. oryzae that possesses the RNA silencing machinery.
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