Klapwijk P M, Scheulderman T, Schilperoort R A
J Bacteriol. 1978 Nov;136(2):775-85. doi: 10.1128/jb.136.2.775-785.1978.
By using the analog noroctopine, mutants of agrobacterium tumefaciens were isolated with altered regulation patterns for the Ti plasmid-borne octopine utilization genes. These could be divided into three classes: (i) strains with a constitutive level of octopine enzymes and a high degree of spontaneous Ti transfer; (ii) one strain with constitutive octopine enzymes but no spontaneous Ti transfer; and (iii) strains with an altered inducibility in which, contrary to the wild-type Ti plasmid, conjugation and octopine utilization were induced by noroctopine. These results are best explained by the activity of a common regulatory gene. In a second step, using homo-octopine, mutants were isolated with lesions preventing the utilization of octopine. All mutations were plasmid borne and did not prevent the induction of tumors. Plasmids of two isolates were characterized by large deletions resulting in a decreased virulence and the absence of octopine in the tumor. With a plasmid carrying an inserted transposon Tn1, a significant number of strains were isolated which were unable both utilize octopine and to transfer the Ti plasmid. This suggests that there may be another common factor--presumably positive--between these traits. Transfer-negative mutants were still virulent. This seems to exclude a role for the conjugative transfer during the process of plant tumor induction. A way to test octopine oxidase by the use of permeable cells is described.
通过使用类似章鱼碱的去甲章鱼碱，分离出了根癌土壤杆菌的突变体，这些突变体对Ti质粒携带的章鱼碱利用基因具有改变的调控模式。这些突变体可分为三类：（i）章鱼碱酶呈组成型水平且Ti自发转移程度高的菌株；（ii）一株章鱼碱酶呈组成型但无Ti自发转移的菌株；（iii）诱导性改变的菌株，与野生型Ti质粒相反，去甲章鱼碱可诱导接合和章鱼碱利用。这些结果最好用一个共同调控基因的活性来解释。第二步，使用高章鱼碱，分离出了阻止章鱼碱利用的突变体。所有突变均由质粒携带，且不阻止肿瘤的诱导。两个分离株的质粒具有大的缺失，导致毒力降低且肿瘤中无章鱼碱。用携带插入转座子Tn1的质粒，分离出了大量既不能利用章鱼碱也不能转移Ti质粒的菌株。这表明在这些性状之间可能存在另一个共同因素——大概是正向的。转移阴性突变体仍然具有毒性。这似乎排除了接合转移在植物肿瘤诱导过程中的作用。描述了一种使用通透细胞检测章鱼碱氧化酶的方法。
