Description:
<jats:p>The processes involved in the formation of crown-gall on the leaves of Kalanchoë daigremontianum have been investigated. The points of infection were treated with fluoro and bromo derivatives of pyrimidine bases and nucleosides at various times before and after the infection. 5-Bromouracil (BU) and 5-Bromodesoxyuridine (BDU) specifically inhibit crown-gall formation during the four-day induction phase. Thymine reverses the inhibition by bromouracil during this same time but has no effect after the end of the induction period. 5-Fluorouracil is only a weak inhibitor of crown-gall formation, whereas 5-fluorodesoxyuridine (FDU) interferes extensively with the entire development of the plant in addition to inhibiting the formation of crown-galls. Our results are consistent with an incorporation of FDU into the autoreduplicative system of the cells. The inhibition by FDU is also much stronger during the induction phase than during the later period of crown-gall growth, so that all results point to a direct participation of a specific crown-gall DNA in the primary changes involved in the production of a crown-gall cell from the host cell.</jats:p>