Jones A L, Thomas C L, Maule A J
John Innes Centre, Norwich Research Park, Colney, Norwich NR4 7UH, UK.
EMBO J. 1998 Nov 2;17(21):6385-93. doi: 10.1093/emboj/17.21.6385.
The relationship between co-suppression and DNA methylation was explored in transgenic plants showing inducible co-suppression following infection with a cytoplasmically replicating RNA virus. Induction resulted in a loss of transgene mRNA and resistance to further infection, factors typical of post-transcriptional gene silencing. In infected plants, de novo methylation of the transgene appeared to precede the onset of resistance and only occurred in plants where the outcome was co-suppression. The methylation was limited to sequences homologous to the viral RNA and occurred at both symmetric and non-symmetric sites on the DNA. Although methylation is predicted to occur in mitotic cells, the virus was found not to access the meristem. A diffusible sequence-specific signal may account for the epigenetic changes in those tissues.
在感染细胞质复制RNA病毒后表现出诱导型共抑制的转基因植物中，研究了共抑制与DNA甲基化之间的关系。诱导导致转基因mRNA丧失以及对进一步感染的抗性，这些都是转录后基因沉默的典型特征。在受感染的植物中，转基因的从头甲基化似乎先于抗性的出现，并且只发生在产生共抑制的植物中。甲基化仅限于与病毒RNA同源的序列，并且发生在DNA的对称和非对称位点上。尽管预计甲基化会发生在有丝分裂细胞中，但发现病毒无法进入分生组织。一种可扩散的序列特异性信号可能解释了这些组织中的表观遗传变化。
