Gheysen G, Villarroel R, Van Montagu M
Laboratorium voor Genetica, Rijksuniversiteit Gent, Belgium.
Genes Dev. 1991 Feb;5(2):287-97. doi: 10.1101/gad.5.2.287.
Agrobacterium tumefaciens is a soil bacterium capable of transferring DNA (the T-DNA) to the genome of higher plants, where it is then stably integrated. Six T-DNA inserts and their corresponding preinsertion sites were cloned from Arabidopsis thaliana and analyzed. Two T-DNA integration events from Nicotiana tabacum were included in the analysis. Nucleotide sequence comparison of plant target sites before and after T-DNA integration showed that the T-DNA usually causes only a small (13-28 bp) deletion in the plant DNA, but larger target rearrangements can occur. Short homologies between the T-DNA ends and the target sites, as well as the presence of filler sequences at the junctions, indicate that T-DNA integration is mediated by illegitimate recombination and that these processes in plants are very analogous to events in mammalian cells. We propose a model for T-DNA integration on the basis of limited base-pairing for initial synapsis, followed by DNA repair at the junctions. Variations of the model can explain the formation of filler DNA at the junctions by polymerase slipping and template switching during DNA repair synthesis and the presence of larger plant target DNA rearrangements.
根癌土壤杆菌是一种能够将DNA（即T-DNA）转移到高等植物基因组中并使其稳定整合的土壤细菌。从拟南芥中克隆了六个T-DNA插入片段及其相应的插入前位点并进行了分析。分析中还纳入了来自烟草的两个T-DNA整合事件。T-DNA整合前后植物靶位点的核苷酸序列比较表明，T-DNA通常仅导致植物DNA中出现小的（13 - 28 bp）缺失，但也可能发生较大的靶位点重排。T-DNA末端与靶位点之间的短同源性以及连接处填充序列的存在，表明T-DNA整合是由非法重组介导的，并且植物中的这些过程与哺乳动物细胞中的事件非常相似。我们基于初始联会时有限的碱基配对，随后在连接处进行DNA修复，提出了一个T-DNA整合模型。该模型的变体可以解释在DNA修复合成过程中通过聚合酶滑动和模板切换在连接处形成填充DNA以及较大的植物靶DNA重排的存在。
