Transformation of Agrobacterium tumefaciens into a Non-oncogenic Species by an Escherichia coli RNA

Abstract

Transforming RNA excreted by s howdomycin-resistant Escherichia coli induces a persistent, heritable, and spectacular change in Agrobacterium tumefaciens B6, a bacterium that carries the oncogenic principle for tumor induction in plants. Transformants possessing new physiological and biochemical properties have completely or partially lost the capacity for tumor induction. They synthetize new ribosomes whose components are profoundly modified. On the basis of biological and biochemical characteristics, one is inclined to consider the completely transformed Agrobacterium tumefaciens as a new species".The production by Escherichia coli of several RNA species in which the concentration of purines exceeds that of pyrimidines is promoted by showdomycin (1, 2). Mutants resistant to this antibiotic synthesize altered RNAs that are no longer complementary to DNA (2). In these mutants ribosomal proteins and several enzymes have been shown to be greatly modified (1, 2). Some possible mechanisms have been proposed (2) to account for sudden appearance of altered RNAs in the presence of showdomycin. One of these predicted the existence in E. coli of an "RNA episome" having purine nucleotides in excess (2, 3). Further investigations confirmed the existence of such an "RNA episome" that is associated with DNA (3). While in wild-type E. coli, this "RNA episome" is apparently not functional and does not dissociate from DNA under normal physiological conditions, it appears to dissociate in the showdomycin resistant (Shor) mutant, since this strain excretes a transforming RNA (3). In brief communications, we have demonstrated the transforming capacity of extracellularly released RNA from E. coli Shor and that of the RNA episome from wild-type bacteria (3). In the present report, we describe the transformation of Agrobacterium tumefaciens by excreted transforming RNA from E coli Shor, accompanied by drastic alteration of the physiological, biochemical, and oncogenic properties of A. tumefaciens. EXPERIMENTAL AND RESULTSIsolation and purification of transforming RNA from E. coliMutants of E. coli ML 30 Shor were obtained as described for E. coli Hfr H M500 Shor (2). The transforming RNA excreted by this mutant was isolated and purified from growth medium as described (2). Among excreted RNA fractions, only those having S values between 5.5 and 6.5 possess the transforming capacity (Fig. 1)

The in vitro Effects of Opines and Other Compounds on DNAs Originating from Bacteria, and from Healthy and Tumorous Plant Tissues

“…This may also be induced under the influence of IAA and small RNA (RNA fragments) [6,25]. Opines do not react in vitro with DNAs from E. coli, from A. tumefaciens strain made nononcogenic by E. coli RNA [4] and from healthy and cancerous human and animal tissue DNAs. It may be concluded from this that plant and A. tumefaciens, oncogenic or not, possess DNAs which have specific and maybe common binding sites for opines.…”

“…Used under identical conditions. DNA originating from E. coli and A. tumefac/ms-transformed B6 Trl [4] did not respond to any opine or carcinogenic compound either for in vitro DNA strand separation or DNA synthesis. …”

Particular RNA Fragments as Promoters of Leukocyte and Platelet Formation in Rabbits

“…DNA-dependent DNA polymerase 1 from E. coli was partially purified and used as the polymerizing enzyme in the absence and presence of RNA fragments and other components necessary for DNA synthesis (8).…”

Activité néformatrice d'acides ribonucléiques extraits de tumeurs végétales

“…La permanence et la nature des caracteres acquis sont des faits retenus pour avancer l'hypothese que la transformation tumorale resulterait de l'introduction d'une partie au moins du genome bacterien dans le materiel genetique de l'hote, Le resultat de diverses experiences d'hybridation (Schilperoort et al 1967, Milo et Srivastava ] (Beljanski et Beljanski 1963), nous avons pense que cette association pourrait les proteger d'une eventuelle degradation par les ribonucleases de la plante lors des experiences d'inoculation.…”