Establishment of quantitative analysis method for genetically modified maize using a reference plasmid and novel...

Area of Science:

• Food Science
• Molecular Biology
• Genetics

Background:

• Accurate quantification of genetically modified (GM) ingredients in processed foods is crucial for regulatory compliance and consumer information.
• Existing methods for GM maize detection may lack the sensitivity required for trace amounts in complex food matrices.

Purpose of the Study:

• To design and validate highly sensitive primer sets and probes for the quantitative analysis of genetically modified (GM) maize in processed food samples.
• To evaluate the impact of primer target region size on the sensitivity of polymerase chain reaction (PCR) assays for GM DNA detection.

Main Methods:

• Design of primer sets and probes targeting specific genetic elements in GM maize: 35S promoter (p35S), nopaline synthase terminator (tNOS), p35S-hsp70 intron, and zSSIIb gene.
• Optimization of PCR assays by comparing primer sets targeting different amplicon lengths (80-101 bp).
• Construction of a reference plasmid (pGMmaize) for real-time PCR (RT-PCR) and validation of standard curves.

Main Results:

• Primer sets targeting shorter regions (80 or 81 bp) demonstrated higher sensitivity compared to those targeting larger regions (94 or 101 bp).
• The 35F1-R1 primer set for p35S (81 bp) showed a 3-log scale increase in sensitivity over a 101 bp target.
• Specific amplification of target DNA fragments was achieved in most GM-labeled food samples using the optimized primer sets.
• RT-PCR using novel primer/probe sets achieved a detection limit of 5 pg of genomic DNA from MON810 maize.

Conclusions:

• Primer sets targeting shorter DNA fragments (80-81 bp) are more sensitive for detecting genetically modified maize in processed foods.
• The developed primer/probe sets, particularly 35F1-R1, offer a highly sensitive method for the quantitative analysis of foreign DNA from GM maize.
• These findings support the reliable detection of GM maize in complex food matrices, aiding in regulatory monitoring and food safety.