Transformation of plant protoplasts with DNA: cotransformation of non-selected calf thymus carrier DNA and meiotic segregation of transforming DNA sequences

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Abstract
With the DNA transformation procedure developed in our laboratory (13) several transformed tobacco SR1 tissues were obtained which, apart from selected and non-selected pTi sequences (T+), also had acquired non-selected calf thymus carrier DNA sequences (C+), being integrated in their nuclear genomes. From one such tissue (cNT4), with a shooty crown gall phenotype and expressing mannopine synthesis activity (Mas+), shoots were grafted and mature, flowering plants (gNT4) were obtained. After cross pollination with wild type SR1 tobacco pollen 49% of the seedlings obtained, had the maternal NT4-like crown gall phenotype and 51% showed wild type (SR1) features. The mannopine locus segregated independently from the locus determining the crown gall phenotype. When screened for integrated (‘transforming’) foreign DNA sequences 97% of the NT4-like seedlings turned out to be C+T+. Most of the SR1-like seedlings, having a wild type tobacco morphology, proved to be transformed as well: roughly a 1:1:1:1 ratio as found for C+T+:C-T+: C+T:C T SR1-like seedlings. Based on the segregation of transforming sequences during meiosis a model is presented showing the integration of these sequences in three different host chromosomes.