Institute of Molecular Biology, Austrian Academy of Sciences, Billrothstrasse 11, A-5020 Salzburg, Austria.
EMBO J. 1989 Mar;8(3):643-9. doi: 10.1002/j.1460-2075.1989.tb03421.x.
Doubly transformed tobacco plants were obtained following sequential transformation steps using two T-DNAs encoding different selection and screening markers: T-DNA-I encoded kanamycin resistance and nopaline synthase; T-DNA-II encoded hygromycin resistance and octopine synthase. A genetic analysis of the inheritance of the selection and screening marker genes in progeny of the doubly tranformed plants revealed that the expression of T-DNA-I genes was often suppressed. This suppression could be correlated with methylation in the promoters of these genes. Surprisingly, both the methylation and inactivation of T-DNA-I genes occurred only in plants containing both T-DNAs: when self-fertilization or backcrossing produced progeny containing only T-DNA-I, expression of the genes on this T-DNA was restored and the corresponding promoters were partially or completely demethylated. These results indicated that the presence of one T-DNA could affect the state of methylation and expression of genes on a second, unlinked T-DNA in the same genome.
经连续两步转化，获得了双转化烟草植株，所用的两个 T-DNA 分别编码不同的选择和筛选标记：T-DNA-I 编码卡那霉素抗性和胭脂碱合成酶；T-DNA-II 编码潮霉素抗性和章鱼碱合成酶。对双转化植株后代中选择和筛选标记基因遗传的分析表明，T-DNA-I 基因的表达常受到抑制。这种抑制可能与这些基因启动子的甲基化有关。令人惊讶的是，T-DNA-I 基因的甲基化和失活仅发生在含有两个 T-DNA 的植物中：当自交或回交产生仅含有 T-DNA-I 的后代时，该 T-DNA 上的基因表达得到恢复，相应的启动子部分或完全去甲基化。这些结果表明，一个 T-DNA 的存在可能影响同一基因组中第二个不连锁 T-DNA 上基因的甲基化状态和表达。
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