Pathogenesis-related proteins in plants and tissues ofNicotiana tabacum transformed byAgrobacterium tumefaciens.

Large amounts of pathogenesis-related (PR) proteins were found inNicotiana tabacum crown gall tissue, following transformation of normal tobacco cells withAgrobacterium tumefaciens. In contrast, PR proteins were not detected in leaves of grafted plants that had been recovered from crown gall tissue even though these plants were still transformed as shown by their inability to form roots and ability to produce octopine. No difference was observed in susceptibility to virus infection between untransformed and transformed plants grafted onto identical rootstocks. The results are discussed in relation to physiological factors controlling PR protein induction and virus resistance.