Otimização de diagnóstico molecular para soja geneticamente modificada

Abstract

According to the Brazilian law, any product containing more than 1% of genetically modified raw materials must inform its condition as genetically modified product on the label (Decree-Law No. 4680 of 2003). Currently genetically modified soy is the most traded soybeans in the world, and its grains can be used as feedstock for a number of foods destined for human consumption, ranging from vegetable oil obtained from the initial milling of seeds, to the subsequent use of these same grains as protein source in processed foods. The aim of this study was to adapt a technology of molecular detection of genetically modified soybeans, for use in the work of verifying the presence of their residues in food products using molecular techniques based on PCR. The extraction of DNA samples from leaf tissue and transgenic soy flour was carried out following the protocol published by Mazza and Bittencourt (2000), with slight modifications, being conducted the evaluation of two independent replicas of each of the analyzed materials. PCR reactions were performed as recommended by Tsai et al. (2010), which recommends the addition of a few cycles of PCR in the "touch-down" mode in order to reduce the specificity effect of the annealing temperature among equipment and reagents from different manufacturers. Primers have been used in PCR reactions, which are capable to identify the presence of the 35S promoter, that corresponds to a fragment of 195 bp, specific from the transgene that exists in soybeans and corn. The verification of GM soybean in soy flour was made from the comparison with a positive identification pattern, established from leaf tissue of transgenic soybeans. The gene fragment obtained by PCR technique was 195 bp for both DNA samples isolated from the soybean leaf tissue as for the DNA samples isolated from soy flour, indicating that the two replicas of the two types of analyzed samples are of transgenic origin. These results indicate that despite the different treatments and adverse conditions by which soybeans are subjected until the transformation of the grain into soy flour, it is possible to perform the verification of transgenic soy in the food chain.