Shen W H, Das S, Hohn B
Friedrich Miescher-Institut, Basel, Switzerland.
Mol Gen Genet. 1992 Jun;233(3):388-94. doi: 10.1007/BF00265435.
We have previously shown that the maize transposable element Ds1 introduced into maize plants by agroinfection can be excised from the genome of geminivirus maize streak virus (MSV). Excision depended strictly on the presence of an active Ac element in the plants. In this study, the excision products or "footprints" left in the MSV genome after Ds1 excision were extensively characterized and the effects of flanking sequences on Ds1 excision were analysed. Most types of footprints obtained were comparable to those described for Ds1 excision in the maize genome, and could be explained by the models proposed for excision of plant transposable elements. In two revertants, however, some terminal sequences of the Ds1 element were found to have been left behind at the excision site. The finding of this novel type of Ds1 footprint indicated that gene conversion events occurred during and/or after Ds1 excision from the MSV genome. A partial deletion of one copy of the 8 bp duplications flanking the Ds1 element had no effect on the frequency or on the types of footprints of Ds1 excision from the MSV genome. Thus, the duplicated 8 bp sequences flanking the transposable element are not involved in Ds1 excision. These results, as well as a statistical analysis of the modifications of the bases flanking the Ds1 element after excision, are discussed in terms of excision models.
我们之前已经表明，通过农杆菌感染导入玉米植株的玉米转座因子Ds1可以从双生病毒玉米条纹病毒（MSV）的基因组中切除。切除严格依赖于植株中存在活性Ac因子。在本研究中，对Ds1切除后留在MSV基因组中的切除产物或“足迹”进行了广泛表征，并分析了侧翼序列对Ds1切除的影响。获得的大多数足迹类型与玉米基因组中Ds1切除所描述的那些相当，并且可以用为植物转座因子切除提出的模型来解释。然而，在两个回复体中，发现Ds1元件的一些末端序列留在了切除位点。这种新型Ds1足迹的发现表明，在Ds1从MSV基因组中切除期间和/或之后发生了基因转换事件。Ds1元件侧翼的8 bp重复序列之一的部分缺失对Ds1从MSV基因组中切除的频率或足迹类型没有影响。因此，转座元件侧翼的重复8 bp序列不参与Ds1切除。根据切除模型讨论了这些结果，以及对Ds1元件切除后侧翼碱基修饰的统计分析。
