Proteomic analysis of a genetically modified maize flour carrying the CRY1AB gene and comparison to the corresponding wild-type

Protein expression in a maize hybrid flour (hereafter called WT) and its corresponding transgenic version resistant to European corn borer (hereafter called BT and carrying a gene encoding for the Bacillus thuringiensis insecticidal protein Cry1Ab) has been studied by means of two-dimensional gel electrophoresis coupled with mass spectrometry. This comparison has been chosen as a model to verify proteomics capability in detecting unexpected differences between near-isogenic lines (differing in the ideal case only for the presence of the transgenic protein). Some unpredictable differences were detected: i) glucose and ribitol dehydrogenase spot was unique of BT maize; ii) endochitinase A spot was unique of WT maize; iii) triosephosphate isomerase 1 and one spot of globulin-1 S were overexpressed while cytosolic 3-phosphoglycerate kinase and one spot of aldose reductase were down-regulated in BT maize with respect to WT. These results outline the potential of the new nontargeted “–omics” technologies (in particular proteomics) in the detection of unexpected, unintended and unwanted variations in Genetically Modified (GM) versus non-GM food comparison and suggest the possible employment of these technologies in substantial equivalence evaluation. Moreover, a reference map for maize flour was built: forty spots, corresponding to twenty-five different proteins, were successfully identified.