Trees without blossom
Male-sterile plants cannot multiply via pollen transfer, but can reproduce via seeds. In order to prevent seeds from forming, the whole flower formation phase must be suppressed. Strategies for achieving this have been developed, particularly in connection with transgenic trees.
The approach is similar to that used to produce pollen-sterile plants, in which a toxin gene (barnase) is used to target and kill off the cells that are involved in the development of the male flower.
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The prerequisite is a suitable "genetic switch" (promoter ), which ensures that the toxin gene is “switched on” only in the targeted cells. During fundamental research into flower development, researchers discovered a whole range of genes that are active at an early stage in the flower precursor cells. The genetic switches for these genes were identified and combined with the barnase gene. After transferring constructs like these, some researchers were able to stop flower formation at an early stage. Efforts to suppress flower formation with the help of the antisense strategy, which is also used to produce sterile plants, have so far been less successful. This strategy can of course be used for biological containment only in crops which are grown for their vegetative parts, such as leaves and wood, rather than for their fruit or seeds. |
It should also be borne in mind that such blossomless trees can no longer be propagated via seed. This means that alternative methods like propagation using cuttings need to be available for poplars.
One aspect that is still problematic is the method’s unreliability: The mechanism for suppressing flower formation does not always work. Isolated intact flowers are frequently formed despite the transgene activity.
The researchers involved in this project therefore want to develop further mechanisms and combine them in the hope that if one system fails, the others will work. A criticism levelled at this containment strategy is that large-scale “blossom-free” tree plantations might have impacts on biodiversity, e.g. on bird and insect populations.
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