Mr Mittendorf, how should one imagine the current situation in the control laboratories? A sample – for example, from a shipload of maize gluten from the USA – must be checked for GMO. How is it done?
You begin with a qualitative screening. That means that you use a PCR test to search for typical DNA elements that are found in the majority of “events” [i.e., specific GM plant – Ed.] that are known worldwide. Normally, samples are tested for the 35-S promoter and the nos terminator. If the probe shows a negative result, you don’t do any further tests, generally. If you find GMO in the probe, then you need to find out its identity. Ultimately, you want to know if these “events” are approved in the EU and, therefore, if the product is suitable for the market. At this point, the GMO analysis can become complex.
What does “complex” mean in this context?
The subsequent PCR analyses are called “construct-specific” or “event-specific” analyses. You can use them to check more precisely which combinations of new DNA elements are contained in the GMO. It’s a process of elimination. You conduct a variety of tests in series until only one specific “event” is in question. In end effect, this means that most often you have to perform a great number of PCR analyses, one after the other, until you get to the end. This is time-consuming.
Can the procedure of GMO detection be simplified by using the DualChip GMO?
Yes. With the new test system, a micro-array, we want to reduce the number of steps towards GMO identification drastically. With DualChip GMO, we can screen one sample with one test for a variety of events. That saves time, and it’s a way to keep step with the increasing number of different “events” world-wide.
What does the rising number of different GMOs that can be found in a sample mean in a practical sense for laboratories?
A few years ago, only exceptional samples contained GMO. Only very rarely did you have to test further after the first screening. At least, this was the case for food, since European industry operates largely without raw materials that potentially might contain a portion of GMO. For example, soybean oil has been replaced by sunflower oil in a lot of products over the past years. However, we’re seeing a tendency now towards more and more positive samples. This means that event-specific tests must be carried out more often. And in practice, this also means that GMO analysis is becoming more and more complicated.
Which GMO can DualChip detect today?
With the GMO chip, we want to broaden GMO analysis, so to speak. With the first version of this test, we could already prove about sixty per cent of the commercial GMO available world-wide. Twenty-four of the GM plants approved in the EU can be definitely identified by the test. Right now, we’re working on an expansion of the chip so that all commercially cultivated GM plants world-wide can be identified in one step. That revolutionises GMO screening from the ground up.
Certainly. But the question remains whether such a test system also catches GMOs that are completely unknown. I’m thinking of the illegal import of Bt 10 maize or LL601 rice from the USA in the past.
Traditional screening strategies can’t pick up many unapproved or completely unknown GMO fragments. When these GMO don’t display the genetic elements that can be found by the first, unspecific screening, then the probe is inconspicuous and is declared GMO-free. So the test can only look straight ahead. But a microarray with numerous GMO-specific features can look left and right, so to speak. This is hardly possible with traditional methods. So when the microarray finds, for example, a combination of GMO marker sequences that is unusual, then this can also mean that an unknown GMO is present in the sample. You can then expand the analysis and start searching more specifically. To answer the question as briefly as I can: one hundred per cent security isn’t possible, even with the DualChip GMO. But the successes are certainly higher.
Mr Mittendorf, thank you very much for the interview.