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Leiden discovery evaluated by world-leading breeding companies

Various companies in the plant biotech industry will test a recent Leiden discovery in their crops. The ‘Pol Theta’ technology is developed in Leiden and makes it possible to reduce undesired side effects during genome engineering of plants.

Genetically transform plants

For many years, agro-biotech has exploited the bacterium Agrobacterium to genetically transform plants, for example to control pest insects or to improve drought tolerance. Agrobacterium is a plant pathogen which causes tumor formation in plants by injecting a piece of its tumor-inducing (Ti) plasmid into plant cells. This T(ransferred )–DNA integrates into the genome of the infected host and expression of bacterial genes converts normal cells into tumor cells. This naturally occurring process of genetic modification has become the most common method for plant transformation, as the T-DNA encoded genes can be replaced by any desired sequence. T-DNA integrates at random positions in the plant genome, thus while this method enables users to obtain transgenic plants, it lacks the ability of controlled targeted integration.


In 2016, the research groups of Paul Hooykaas at the Institute of Biology Leiden (IBL) and Marcel Tijsterman at the Leiden University Medical Center (LUMC) discovered that the enzyme polymerase theta is essential for the random integration of Agrobacterium T-DNA. The finding is a breakthrough for the development of more efficient protocols for targeted genome modification, hence facilitating the production of improved, tailor-made crop plants. Hooykaas and Tijsterman introduced this concept in a publication in 2016 in Nature Plants.


The Leiden researchers also decided to apply for patent. The patent describes methods to completely eradicate random integration, thus enabling targeted genome editing and engineering in plants as well as facilitating transient non-integrated expression. The patent covers the envisaged application in various plant species, because of the broad conservation of polymerase theta in plant species including crops such as corn, wheat, rice and soy.


Within the plant biotech industry, a growing number of companies are interested in evaluating and further developing the invention for applications in their crop species. The Leiden technology transfer office now reached evaluation and research agreements with two of the largest seed producers in the world. These agreements allow the Leiden research team to study the process of T-DNA integration and the plant factors involved in more detail, while the companies will assess the efficiency of the Pol Theta technology in crop species.

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