Stability and expression of transferred DNA in F1 tobacco transformants studied at various states of differentiation.

Grafts from the SR1 tobacco crown-gall lines NT1 (having a deletion eliminating part of the transferred (TL)-DNA auxin locus) and NT2 (having an IS60 insertion in gene 2 of this auxin locus) were cross-pollinated with pollen from nontransformed SR1 tobacco plants. One half of the resulting F1 progeny resembled the female parent ("transformed" NT1-like and NT2-like seedlings respectively) and one half resembled the male parent ("non-transformed" SR1-like seedlings). For three states of differentiation (callus, shoot, graft) all phenotypic markers of the transformed seedlings studied were identical to those of the transformed female parent.

T-DNA rearrangements due to tissue culture: somaclonal variation in crown gall tissues.

After three years of apparent stability in tissue culture, the single cell derived shooty crown gall line sNT1.013 produced a revertant shoot which had switched from non-rooting (Rod(+)) and octopine synthesizing (Ocs(+)) to Rod(-) Ocs(-), indicating that in this revertant TL-DNA genes 4 (causing the Rod(+) trait) and gene 3 (causing the Ocs(+) trait) had been inactivated. Southern blots revealed that the inactivation of these T-DNA genes was the result of a considerable rearrangement of DNA sequences, accompanied by deletions and possibly also by DNA amplifications.