Department of Biological Sciences, Lilly Hall of Life Sciences, Purdue University, West Lafayette, IN 47907.
Proc Natl Acad Sci U S A. 1987 Apr;84(7):1881-5. doi: 10.1073/pnas.84.7.1881.
Agrobacterium tumefaciens transfers the T-DNA portion of its Ti plasmid to the nuclear genome of plant cells. Upon cocultivation of A. tumefaciens strain A348 with regenerating tobacco leaf protoplasts, restriction endonuclease fragments of the T-DNA were generated that are consistent with double-stranded cleavage of the T-DNA at the border sequences. The T-DNA border cleavage was also induced by acetosyringone, a compound that induces many of the virulence genes. T-DNA cleavage did not occur in Agrobacterium strains harboring Tn3-HoHo1 insertions in the virA, -D, or -G genes. Insertion mutations in virB, -C, or -E did not have any effect on the T-DNA cleavage. Complementation of the mutations in virA, -D, or -G with cosmids containing the respective wild-type genes restored the T-DNA cleavage. Since virA and -G are essential in regulating the expression of other vir genes in response to plant signal molecules, the virD gene product(s) appear to mediate double-stranded T-DNA border cleavage.
根瘤农杆菌将其 Ti 质粒的 T-DNA 部分转移至植物细胞核基因组。在 A348 型根瘤农杆菌与再生烟草叶原生质体共培养时，生成了与 T-DNA 在边界序列处双链断裂一致的 T-DNA 限制内切酶片段。乙酰丁香酮（一种诱导许多毒力基因表达的化合物）也可诱导 T-DNA 边界断裂。携带 Tn3-HoHo1 插入物的 virA、-D 或 -G 基因的根瘤农杆菌菌株中未发生 T-DNA 断裂。virB、-C 或 -E 中的插入突变对 T-DNA 断裂没有任何影响。用包含相应野生型基因的 cosmid 互补 virA、-D 或 -G 中的突变，恢复了 T-DNA 断裂。由于 virA 和 -G 在调节其他 vir 基因的表达以响应植物信号分子方面是必需的，因此 virD 基因产物似乎介导了 T-DNA 双链边界断裂。
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