Shaw C H, Watson M D, Carter G H, Shaw C H
Nucleic Acids Res. 1984 Aug 10;12(15):6031-41. doi: 10.1093/nar/12.15.6031.
At either end of the nopaline Ti-plasmid T-region resides a copy of a 25 bp repeated element. The normal T-DNA endpoint is 1 bp internal of the right copy, with the transcription initiation site of the nopaline synthase (nos) gene being approximately 300 bp away in the same direction. Here we describe results which demonstrate that deletion of any combination of sequences between the nos initiation site and the right copy of the 25 bp repeat does not affect oncogenicity. Thus a mutant retaining the right copy and only 3 bp internal of it is indistinguishable from the wild type parent in its oncogenic properties. However deletion of a further 39 bp, including complete removal of the right copy abolishes crown gall tumour formation on Kalanchöe and tobacco. From these results we infer that unlike the left border, the right copy of the 25 bp repeat is required for T-DNA transfer and/or integration. This is the first conclusive demonstration of the involvement of a copy of the repeats in this process.
胭脂碱型Ti质粒T区的两端各有一个25bp重复元件的拷贝。正常的T-DNA末端位于右侧拷贝内部1bp处，胭脂碱合酶（nos）基因的转录起始位点在同一方向约300bp处。在此我们描述的结果表明，nos起始位点与25bp重复序列右侧拷贝之间的任何序列组合缺失均不影响致癌性。因此，一个保留右侧拷贝且仅其内部3bp的突变体在致癌特性上与野生型亲本无差异。然而，再缺失39bp，包括完全去除右侧拷贝，则会消除落地生根和烟草上冠瘿瘤的形成。从这些结果我们推断，与左边界不同，25bp重复序列的右侧拷贝是T-DNA转移和/或整合所必需的。这是重复序列拷贝参与此过程的首个确凿证据。
