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Conventional PCR tests for GMOs only test for one GMO at a time. With more and more GMOs being developed, tests for will only be getting more expensive. The need for multiplex GMO tests, which would detect many GMOs at the same time, is therefore acute. Co-Extra researchers are now working on ways to detect the presence of many GMOs at once. Although multiplex detection is within reach, simultaneously determining their quantities remains a great technical challenge.

The first concern with developing multiplex PCR methods is identifying the gene sequences that the test will target. Research are compiling an ongoing list of genetic sequences that are characteristic for certain crops and GMOs.

The genetic sequences that can be targeted include the sequences of specific transferred genes or sequences for the commonly used genetic building blocks that often accompany transgenes. Other useful gene sequences are those that code for genes specific to a certain crop. That way, a test can determine if a food contains unexpected traces of crops like soybeans, barley, or rice.

Flourescent probes are used in quantitative PCR to track how fast a gene of interest is being copied. To simultaneously measure the amounts of different certain genes in a single sample, Co-Extra researchers are tagging target genes with different coloured fluorescent probes. That way, signals coming from different target genes can be isolated to find out exactly which of the GMOs have been found.

To start, researchers are taking genes specific to barley or wheat and are measuring their quantities in duplex - which means measuring the quantity of two genes simultaneously.

A list of genetic sequences suitable for targeting for multiplex testing has been compiled and made available. The document is open to additions as more suitable target sequenes are determined.

As a step toward multiplex tests for different GMOs, researchers have developed a method of simultaneously testing for the presence and quantity of what and barley in unknown samples. One set of targeting primers can amplify a homologous, single-copy gene found both crops. Flourescent probes with different colours are used to quanitfy the genes from the respective crops, with each color being specific to one of the cereals. This technique could be used to target several similar, but slightly different transgenes, permitting for example the multiplex analysis of several of the most prevelent transgenes.

Recent publication: 
Novel reference gene, PKABA1, used in a duplex real-time polymerase chain reaction for detection and quantitation of wheat- and barley-derived DNA (Ronning SB, Berdal KG, Andersen CB, Holst-Jensen A.).