Nov 18, 2009

Research Confinement

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New research projects

Biological confinement of new genes

Between 2008 and 2011, a number of different research projects are developing and checking methods for containing the spread of genetically modified plants (confinement).

A confinementstrategy makes sense when plants are being used for the production of functional foods or for producing industrial or pharmaceutical substances, where any outcrossing or spreading of these plants would be undesirable. A range of very different research approaches are currently being tried on model plants in an attempt to implement confinement strategies. For instance, researchers are testing whether male-sterile plants, plants with transgene-free pollen and plants that fertilize themselves within closed flowers meet the requirements of a confinement system.

Sterility concept: Plants without pollen

Male-sterile plants are not able to produce functional pollen. The use of naturally-occurring sterile plants as source material for genetic modifications could be a suitable method of biological confinement. However, naturally-occurring male sterility can be reversed by the activity of certain genes or by extreme environmental conditions. At the Julius Kühn Institute in Quedlinburg a team is investigating the stability of this trait on various male-sterile maize varieties under different environmental conditions.

At the Johann Heinrich von Thünen-Institut (vTI - the Federal Research Institute for Rural Areas, Forestry and Fisheries) in Großhansdorf, researchers are using genetically modified poplars to test a sterility concept in which the anthers produce a cytotoxin that prevents pollen formation.

Transgene-free pollen

Several research projects are looking at new plant-breeding approaches for producing plants with transgene-free pollen. There are two different strategies:

• Plastid transformation as an alternative to transformation of the nuclear genome
• Removal of the transgene during pollen formation with the help of special enzymes

In plastid transformation, transgenes are ferried into the plastid DNA instead of into the DNA of the cell nucleus, as they are in nuclear transformation. Plastids are self-contained units in the cell plasma of green plants that have their own small genome. Most agricultural crop plants inherit plastids maternally, i.e. not via pollen. By producing and cultivating transplastomic plant lines it may be possible to prevent, or at least restrict, the spread of the transgenes via outcrossing.

A number of research projects at the Max Planck Institute in Potsdam and at the Universities of Munich and Rostock, are developing plastid transformation for maize and oilseed rape. Field trials are being conducted to test the reliability of plastid transformation as a confinement strategy. Since transplastomic oilseed rape and maize lines will not be available until part-way through the research project, the field trials in the first two years are being conducted with the model plants petunia and Arabidopsis.

A new approach involves the targeted removal of the transgene during pollen formation. This process makes use of recombinases – special enzymes that can cut DNA segments out of the genome at the site of specific recognition sequences. The resulting pollen is then transgene free. This method is being developed on maize at the University of Hamburg and on poplars at the Institute for Forest Genetics, Johann Heinrich von Thünen Institute (vTI).

Self-pollination

Plants that pollinate and fertilize themselves inside closed flowers are called cleistogamic. This severely restricts pollen-mediated gene transfer to neighbouring plants. Using a transgenic cleistogamic oilseed rape line, the Julius Kühn Institute (JKI) in Quedlinburg is testing whether cleistogamy, which occurs fairly infrequently in nature, can be used as a biological confinement strategy.

Inhibiting germination

Potatoes propagate via tubers which germinate after a period of dormancy. If potato tubers are left on the field after harvesting, they can lead to unwanted volunteer plants appearing in the following crop. A research project at Friedrich-Alexander University Erlangen-Nuremberg aims to inhibit the germination process through a targeted genetic modification, in order to prevent potatoes spreading through the emergence of volunteer plants.