Smith Oliver, Clapham Alan J, Rose Pam, Liu Yuan, Wang Jun, Allaby Robin G
School of Life Sciences, Gibbet Hill Campus, University of Warwick, Coventry CV4 7AL, UK.
The Austrian Archaeological Institute; Cairo Branch, Zamalek, Sharia Ismail Muhammed, Apt 62/72, Cairo, Egypt.
Sci Rep. 2014 Jul 4;4:5559. doi: 10.1038/srep05559.
Genomic methylation is variable under biotic and abiotic stresses in plants. In particular, viral infection is thought to significantly increase genomic methylation with particularly high activity around transposable elements. Here we present the genomic methylation profiles of grains of archaeological barley (Hordeum vulgare) from several strata from a site in southern Egypt, from the Napatan to the Islamic periods (800 BCE - 1812 CE). One sample tested positive for viral infection and exhibits an unusually high degree of genomic methylation compared to the rest. A decreasing trend in global methylation levels according to deposition date shows in-situ de-methylation of 5-methylcytosine, which can be described as a diagenetic process. This is most likely a deamination mediated de-methylation process and is expected to lead to 5 mC > T base modifications in addition to the C > U modifications due to cytosine deamination, so represents a time-dependent process of DNA diagenesis in ancient DNA.
植物基因组甲基化在生物和非生物胁迫下是可变的。特别是，病毒感染被认为会显著增加基因组甲基化，在转座元件周围的活性尤其高。在这里，我们展示了来自埃及南部一个遗址几个地层的考古大麦（Hordeum vulgare）籽粒的基因组甲基化图谱，时间跨度从纳帕塔时期到伊斯兰时期（公元前800年 - 公元1812年）。一个样本检测出病毒感染呈阳性，与其他样本相比，其基因组甲基化程度异常高。根据沉积日期，全球甲基化水平呈下降趋势，表明5 - 甲基胞嘧啶发生原位去甲基化，这可被描述为一个成岩过程。这很可能是一个脱氨介导的去甲基化过程，预计除了由于胞嘧啶脱氨导致的C > U修饰外，还会导致5mC > T碱基修饰，因此代表了古代DNA中DNA成岩作用的一个时间依赖性过程。
