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Mechanisms of Tumor Induction in Crown Gall

I. Production and Pathogenicity of Spheroplasts of Agrobacterium tumefaciens¹

Laboratory of Plant Morphogenesis, Manhattan College, Bronx, New York

The hypothesis that crown gall tumorigenesis requires the formation of spheroplasts was tested by comparing the tumorinducing ability of populations of both permanent and revertable spheroplasts of Agrobacterium tumefaciens with that of populations of the typical rod form of the bacterium. Permanent spheroplasts produced by serial transfers in medium containing 0.005 MD-methionine did not produce tumors in either Kalanchoe or Boston daisy. The efficiency of tumor induction in Kalanchoe stems was lower for glycine-induced revertable spheroplasts than for rod forms. In addition, a progressive decrease in tumorinducing ability, detectable within 30 min after the addition of glycine to bacterial cultures, was also demonstrated in primary pinto-bean leaves by means of the quantitative assay of Lippincott and Heberlein. A study of attenuation among glycine-resistant clones of the crown gall bacterium revealed that the capacity for tumor induction is not lost simultaneously for all hosts. It was also observed that attenuated, glycine-resistant mutants may regain the capacity for tumor production with no detectable change in the level of glycine resistance.

¹ This work was carried out over a period of several years. The early investigations were supported as follows: Beardsley by NSF Grant G17870; Stonier by PHS Grant NIH, C2944 administered by Professor A. C. Braun, Rockefeller University; Lipetz by PHS Post-Doctoral Fellowship CF7607. More recently, we have been supported by PHS grants CA06956 to R. B., CA06957 to T. S., and CA06955 to J. L. Parsons was supported by NSF Undergraduate Research Participation Grant 5/70/5/410-2496 administered by Brother C. Edward Quinn. The Laboratory of Plant Morphogenesis is supported in part by PHS Institutional Grant RC1193, Damon Runyon Memorial Fund Grant DRM710, and the Christine Sonntag Foundation for Cancer Research.

Received 3/29/66.