Detection of transgenic and endogenous plant DNA in blood and organs of Nile tilapia, Oreochromis niloticus fed a diet formulated with genetically modified soybean meal
Anxiety regarding the fate of ingested transgenic DNA in farmed fish fed genetically modified (GM) soybean meal (SBM) has been raised with regard to human consumption. The objective of this study was to detect possibility of gene transfer of transgenic and endogenous DNA fragments in Nile tilapia (Oreochromis niloticus) blood and organs after consumption of a GM SBM diet. Nile tilapias with an average weight of 75.0 g were fed diets containing 48% GM or non-GM SBM for 21 days. During this period, a GM SBM diet was fed to fish for 12 days, and then switched to feed with non-GM SBM for 9 days for determining the residual span of the transferred cauliflower mosaic virus (CaMV) 35S promoter fragment. Blood, spleen, liver, intestine, kidney, and muscle tissues were taken (n = 10) every three days during the feeding period. Total DNA was extracted from the samples and analyzed by polymerase chain reaction (PCR) for determining the presence of a 108-bp fragment of the CaMV 35S promoter and a 144-bp fragment of the soybean chloroplast-specific DNA. Low-copy chloroplast-specific DNA fragment was detected in all organ and tissue samples and the majority of intestinal samples of fish fed GM SBM diet. Similarly, a low number and faint signals of the CaMV 35S promoter fragments were detected in all organ samples except muscle of fish fed the GM SBM diet, while none were detected 3 days after changing to a non-GM SBM diet. A very low frequency of transmittance to muscle and organs of fish was confirmed. It is recognized that the low copy number of transgenic DNA in the GM SBM diet is a challenge to their detection in tissues. These results suggested that transgenic DNA would be processed in the gastrointestinal tract in a similar manner with conventional plant DNA
