Persistence of DNA in the environment could increase the
likelihood of horizontal gene transfer in microorganisms by
transduction, transformation, and conjugation. Gebhard and
Smalla (1998) have demonstrated that transgenic sugar beet
DNA can be transferred to bacteria, and Stotzky (2000)
have reported that the persistence of clay-bound DNA is
related to its horizontal movement in soil. Here, we
performed PCR analysis for DNA extracted from soil under
the litter bags. Our results showed that neither the nos
terminator nor hpt was amplified (data not shown), but we
did find the 35S promoter in soil collected beneath leaf
samples for up to 3 months (Fig. 2). We cannot yet explain
why only that 35S promoter, among all transgenes, was
detectable in our study.