Assessment of DNA degradation induced by thermal and UV radiation processing: Implications for quantification of genetically modified organisms.

DNA quality is an important parameter for the detection and quantification of genetically modified
organisms (GMO’s) using the polymerase chain reaction (PCR). Food processing leads to degradation of
DNA, which may impair GMO detection and quantification. This study evaluated the effect of various processing
treatments such as heating, baking, microwaving, autoclaving and ultraviolet (UV) irradiation on
the relative transgenic content of MON 810 maize using pRSETMON-02, a dual target plasmid as a model
system. Amongst all the processing treatments examined, autoclaving and UV irradiation resulted in the
least recovery of the transgenic (CaMV 35S promoter) and taxon-specific (zein) target DNA sequences.
Although a profound impact on DNA degradation was seen during the processing, DNA could still be reliably
quantified by Real-time PCR. The measured mean DNA copy number ratios of the processed samples
were in agreement with the expected values. Our study confirms the premise that the final analytical
value assigned to a particular sample is independent of the degree of DNA degradation since the transgenic
and the taxon-specific target sequences possessing approximately similar lengths degrade in parallel.
The results of our study demonstrate that food processing does not alter the relative quantification
of the transgenic content provided the quantitative assays target shorter amplicons and the difference in
the amplicon size between the transgenic and taxon-specific genes is minimal.