Is the Fungus Magnaporthe Losing DNA Methylation?
Is the Fungus Magnaporthe Losing DNA Methylation?
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DOI：
10.1534/genetics.113.155978
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发表时间：
2013-11-01
期刊：
影响因子：
3.3
通讯作者：
Nakayashiki, Hitoshi
中科院分区：
文献类型：
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作者：
Ikeda, Ken-ichi;Ba Van Vu;Nakayashiki, Hitoshi
长末端重复反转录转座子，Magnaporthe gypsy样元件（MAGGY），已被证明是靶向胞嘧啶甲基化的一个子集的Magnaporthe magnaporthe田间分离。对来自甲基化熟练（Br 48）和甲基化缺陷（GFSI 1 -7-2）分离株之间遗传杂交的F-1后代的分析表明，MAGGY元件的甲基化受单个显性基因控制。定位克隆，然后基因破坏和互补实验表明，负责的基因是DNA甲基转移酶，MoDMT 1，一个直系同源的粗糙脉孢菌Dim-2。对60个稻瘟病菌田间分离物的MAGGY甲基化分析表明，来自水稻、谷子、小麦、谷子和牛筋草的42个菌株甲基化能力强，来自狗尾草、绿色狗尾草、日本稷、鱼雷草、马唐和马唐的18个菌株甲基化能力差。表型分析表明，MoDMT 1在真菌的发育和致病性中没有发挥重要作用。定量聚合酶链反应分析表明，基因组MAGGY元素的平均拷贝数是没有显着差异甲基化缺陷和精通领域的分离物，即使MAGGY转录水平普遍较高，在前一组。MoDMT 1基因序列在甲基化缺陷的菌株表明，至少有三个独立的突变负责MoDMT 1功能的丧失。总的来说，我们的数据表明，MoDMT 1不是真菌的自然生命周期所必需的，并提出了Magnaporthe属可能在进化时间尺度上失去DNA甲基化机制的可能性。
The long terminal repeat retrotransposon, Magnaporthe gypsy-like element (MAGGY), has been shown to be targeted for cytosine methylation in a subset of Magnaporthe oryzae field isolates. Analysis of the F-1 progeny from a genetic cross between methylation-proficient (Br48) and methylation-deficient (GFSI1-7-2) isolates revealed that methylation of the MAGGY element was governed by a single dominant gene. Positional cloning followed by gene disruption and complementation experiments revealed that the responsible gene was the DNA methyltransferase, MoDMT1, an ortholog of Neurospora crassa Dim-2. A survey of MAGGY methylation in 60 Magnaporthe field isolates revealed that 42 isolates from rice, common millet, wheat, finger millet, and buffelgrass were methylation proficient while 18 isolates from foxtail millet, green bristlegrass, Japanese panicgrass, torpedo grass, Guinea grass, and crabgrass were methylation deficient. Phenotypic analyses showed that MoDMT1 plays no major role in development and pathogenicity of the fungus. Quantitative polymerase chain reaction analysis showed that the average copy number of genomic MAGGY elements was not significantly different between methylation-deficient and -proficient field isolates even though the levels of MAGGY transcript were generally higher in the former group. MoDMT1 gene sequences in the methylation-deficient isolates suggested that at least three independent mutations were responsible for the loss of MoDMT1 function. Overall, our data suggest that MoDMT1 is not essential for the natural life cycle of the fungus and raise the possibility that the genus Magnaporthe may be losing the mechanism of DNA methylation on the evolutionary time scale.