SPIROS PARAMITHIOTIS¹, ANASTASIA ADRAKTA¹, KYRIAKI SIGALA², ELEFTHERIOS H. DROSINOS¹*, CHARALAMPOS PROESTOS²
*Corresponding author
1. Agricultural University of Athens, Dept. of Food Science and Human Nutrition, Laboratory of Food Quality Control and Hygiene, Iera Odos 75, GR-118 55 Athens, Greece
2. National and Kapodistrian University of Athens, Dept. of Chemistry, Laboratory of Food Chemistry, Panepistimiopolis Zografou, GR-15771 Athens, Greece

Abstract

The aim of the present study was to detect DNA sequences originating from GMOs in milk and dairy products commercially available in Greece. A total of 135 samples were examined, including 31 yoghurt, 29 milk and 75 cheese samples. The matrix approach was applied, including detection by specific polymerase chain reaction (PCR) of the screening elements P-35S, T-nos, CP4-epsps, bar and pat. It is suggested that utilization of the junctions between P-35S and the pat gene as well as between ctp2 and CP4-epsps might be at least problematic and might even lead to misinterpretation of the results due to the occurrence of polylinker sequences of varying length. Furthermore, accurate and efficient detection of at least P-35S may require the use of more than one primer pair. The minimum detectable amount of DNA was 0.078 pg per screening element or 0.39 pg of total screening element DNA in all categories of dairy products examined. Absence of the GMO screening elements in the dairy products examined has been verified.

INTRODUCTION

Among the different analytical procedures that have been described for GMO detection, DNA-based ones are favored and polymerase chain reaction (PCR) is widely applied, since DNA is more process resistant as a molecule and PCR-based methods are characterized by enhanced sensitivity and flexibility (1). The target sequence as well as the methodology applied, may vary according to the aim of the study; if the aim of the study is quantitative detection of genetically modified (GM) content, then real time PCR protocols should be applied, such as in the study by Samson et al. (2), in which the quantitative detection of Roundup Ready^® soybean event GTS 40-3-2 in food was achieved through real time PCR using TaqMan^® minor groove binder-non-fluorescent quencher (MGB-NFQ) chemistry. On the other hand, when the purpose of the study is qualitative screening, then PCR aims to amplify the most common genetic elements present in GM constructs, referred to as screening elements. Specific promoters and terminators such as the 35S promoter from cauliflower mosaic virus (P-35S) and the terminator from the nopaline synthetase gene of Agr ...