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A new technique capable of identifying unregistered GMOs

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News of 19/02/2021

Thanks to a technique developed by the ANSES Plant Health Laboratory, at the site in Angers, it is now easier to identify an unregistered DNA sequence in a genetically modified organism (GMO).

The genetic modification of organisms by transgenesis consists in introducing one or more genes from another species into their genome. GMOs are generally detected by searching for DNA sequences frequently used to obtain them. These sequences enable the cells of the modified organism to correctly express the inserted gene. This is the case, for example, of the 35S promoter (p35S), which signifies the start of a gene.  It is commonly used to produce GM plants. Its detection indicates the presence of a GMO but does not provide information about which gene was introduced or what its function is. To learn more, it is necessary to screen for genes known as being used in transgenesis. But what if no listed genes are found? The new identification strategy developed by ANSES's Plant Health Laboratory eliminates the need for the tedious techniques that previously had to be used.

Reference activity for genetically modified plants
The Bacteriology, Virology & GMO (BVO) Unit of ANSES's Plant Health Laboratory, based in Angers, has a mandate as National Reference Laboratory for the detection of GMOs. In this capacity, it is responsible for developing and validating official analytical methods. 

Finding without knowing what to look for

The developed technique is able to rapidly identify an unknown gene sequence. To that end, the organism's DNA is broken down into fragments of around 6000 DNA base pairs (the genome of a plant can contain several million base pairs). These originally linear fragments are circularised; this step is important for the method's success. They are then amplified using the inverse polymerase chain reaction (PCR) technique. For this amplification, a known start point is required; here it is the p35S promoter. Only DNA pieces containing it will be amplified. An end point is also necessary, and this is where the circular fragments become relevant: amplification stops at the start point, enabling the entire fragment to be duplicated. Since the p35S promoter is followed by the targeted transgene, its sequence can be obtained by simply sequencing the amplified DNA.

An effective technique for all GMOs

The method was successfully tested on a transgenic petunia. The results were published in Scientific Reports. The technique is relatively inexpensive and can sequence a new GMO within two days. It applies to all types of genetically modified organisms, including plants, animals and bacteria. There may be other applications as well, especially in the medical sector. Small gene sequences, called transposable elements, change positions in the genome and sometimes cause disease. This identification technique could be used to determine where they are inserted and understand how their location influences the occurrence of disease.

 
Did you know? 
No open-field cultivation of genetically modified organisms is authorised in France; however, such GMOs can be imported. Animal feed frequently contains GM plants. Trace levels of GMOs are found in human food; labelling is required for any foods containing more than 1%. GMO producers allowed to market their products in Europe must specify the transgene sequences used. This enables them to be detected when identifying a GMO. An unregistered GMO is prohibited by definition.