Yajko D M, Hegeman G D
J Bacteriol. 1971 Dec;108(3):973-9. doi: 10.1128/jb.108.3.973-979.1971.
When Agrobacterium tumefaciens cells grown in the presence of tritiated thymidine to label specifically the bacterial deoxyribonucleic acid (DNA) are incubated with carrot root tissue for short periods of time, an appreciable fraction of the label becomes firmly associated with the root tissue. Such association is not observed in identical experiments when A. tumefaciens cell ribonucleic acid or protein are labeled. The extent of the retention of thymidine-derived label from bacterial cells by the root tissue in experiments with A. radiobacter and poorly tumorigenic strains of A. tumefaciens is significantly less than that afforded by tumorigenic strains of A. tumefaciens but greater than the level afforded by Escherichia coli. Transfer of DNA-specific label from A. tumefaciens to carrot root discs is not enhanced by treatments designed to provoke lysis of the bacterial cells, nor is it decreased by addition of deoxyribonuclease or excess unlabeled thymidine to the incubation medium. Bacterial cell-to-plant cell contact is necessary for transfer. Unlabeled A. radiobacter cells decrease in a competitive manner transfer of label when mixed with labeled A. tumefaciens cells. These findings suggest that transfer of DNA from A. tumefaciens to plant tissue after binding of the bacterial cells to specific plant tissue site(s) is a necessary feature of the mechanism by which A. tumefaciens provokes tumors in plants and provides an experimental technique of potentially great value in study of the early steps in the process of tumor induction by A. tumefaciens.
当在含有氚标记胸腺嘧啶核苷的条件下培养根癌土壤杆菌细胞，以便特异性标记细菌的脱氧核糖核酸（DNA），并将其与胡萝卜根组织短时间孵育时，相当一部分标记会牢固地与根组织结合。在相同实验中，当根癌土壤杆菌细胞的核糖核酸或蛋白质被标记时，未观察到这种结合。在使用放射土壤杆菌和根癌土壤杆菌低致瘤性菌株进行的实验中，根组织从细菌细胞中保留胸腺嘧啶核苷衍生标记的程度明显低于根癌土壤杆菌致瘤性菌株，但高于大肠杆菌提供的水平。旨在引发细菌细胞裂解的处理不会增强根癌土壤杆菌的DNA特异性标记向胡萝卜根圆盘的转移，向孵育培养基中添加脱氧核糖核酸酶或过量未标记的胸腺嘧啶核苷也不会降低这种转移。细菌细胞与植物细胞的接触对于转移是必要的。当未标记的放射土壤杆菌细胞与标记的根癌土壤杆菌细胞混合时，会以竞争方式减少标记的转移。这些发现表明，在细菌细胞与特定植物组织位点结合后，根癌土壤杆菌的DNA向植物组织的转移是根癌土壤杆菌在植物中引发肿瘤机制的一个必要特征，并为研究根癌土壤杆菌诱导肿瘤过程早期步骤提供了一种具有潜在重大价值的实验技术。
