'Tabac anergié' tissue has been used by many investigators as a habituated tobacco cell line. In this study, we have found sequences which are homologous to approximately 9 megadaltons of an Agrobacterium octopine-type plasmid in DNA isolated from 'Tabac anergié' tissue. These T-DNA sequences were shown to be the same 'core DNA' sequences found to be present in several other unorganized tumor lines which have been studied in our laboratory. The T-DNA was also shown to be integrated into plant DNA. Thus, the 'Tabac anergié' tissue is a crown gall tumor induced by a strain of Agrobacterium tumefaciens containing an octopinetype plasmid. These results indicated that the plants regenerated from 40 clones of the 'Tabac anergié' line by Sacristán and Melchers (1977) were actually reverted plants obtained from an unorganized crown gall tumor, kept in culture for more than 25 years. It is necessary to re-evaluate observations and conclusions which have been based upon 'Tabac anergié' being a habituated tissue.
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