The fate of recombinant plant DNA in soil

Genetically modified tobacco containing a bacterial gentamicin resistance gene (aacC1) was developed and cultured in a field to monitor the fate of plant DNA in soil for up to 3 years. We determined whether DNA persisted as extracellular molecules or as genetic information in soil bacteria, by extracting total DNA after in situ lysis or bacterial DNA after physical extraction of bacteria from the soil. The recovered DNAs were used in PCR reactions with primers targeting the aacC1 gene coding for gentamicin resistance, tobacco-specific sequences in the ribulose biphosphate carboxylase/oxygenase gene and sequences specific to genetically modified tobacco inside the T-DNA. Plant DNA was found to persist in the soil for several months, but no longer than 3 years. There was no evidence that the resistance gene from the plant had been transferred to soil bacteria, although primers targeting the aacC1 gene provided positive PCR signals in all soil samples. (C) Elsevier, Paris.