Hehl R, Baker B
Plant Gene Expression Center, United States Department of Agriculture, Albany, California 94710.
Plant Cell. 1990 Aug;2(8):709-21. doi: 10.1105/tpc.2.8.709.
The maize controlling element Activator (Ac) transposes autonomously from an integrated T-DNA vector to new sites in the genomes of tobacco and other heterologous plant species. Here we demonstrate that critical functions required for transposition of Ac in maize are conserved in tobacco and that Ac transposes at high frequency for at least five generations. Ac structure and terminal sequences are conserved upon transposition and a characteristic 8-bp duplication of target sequences is generated upon integration. Ac remains unmethylated, transcriptionally active, and capable to trans-activate transposition of the nonautonomous Dissociation (Ds) element throughout several generations. In tobacco, as in maize, Ac transposes adjacent to low copy or unique DNA, and transcriptional analysis of unique target DNA provides evidence that an Ac element transposed into a gene. In maize, increasing copies of Ac delay the timing and reduce the frequency of early transposition of Ac and Ds. In tobacco, increasing copies of Ac correlate with an increased frequency of Ds trans-activation. These data firmly establish that the Ac and Ds transposable elements are versatile genetic tools well suited for use as insertional mutagens and demonstrate that thorough investigation of mechanism and regulation of transposition is facilitated in heterologous settings.
玉米控制元件激活子（Ac）能从整合的T-DNA载体自主转座至烟草及其他异源植物物种基因组中的新位点。在此，我们证明了Ac在玉米中转座所需的关键功能在烟草中保守，且Ac能高频转座至少五代。转座时Ac的结构和末端序列保守，整合时会产生特征性的8碱基对靶序列重复。Ac保持未甲基化、转录活跃状态，并能够在几代中反式激活非自主解离元件（Ds）的转座。在烟草中，如同在玉米中一样，Ac转座至低拷贝或单拷贝DNA附近，对单拷贝靶DNA的转录分析提供了Ac元件转座进入基因的证据。在玉米中，Ac拷贝数增加会延迟Ac和Ds早期转座的时间并降低其频率。在烟草中，Ac拷贝数增加与Ds反式激活频率增加相关。这些数据确凿地证明，Ac和Ds转座元件是非常适合用作插入诱变剂的通用遗传工具，并表明在异源环境中便于对转座机制和调控进行深入研究。
