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Gene Technology Helps Plants Defy Drought

Hereditary factors make plants more resistant to aridity

Scientists from the University of Bonn have identified a gene which makes plants more resistant to a shortage of water. They have constructed a variety in which the drought gene was frequently deployed. The gratifying result is that the genetically modified version can withstand aridity appreciably longer than its cousin in the wild. The results have been published in the latest edition of The Plant Journal (vol. 35 issue 4 pp. 452-464). On a long-term basis they may contribute to developing crops which are resistant to drought.

The resurrection plant is well named: in droughts this South African plant shrivels up into an unsightly brownish mass, but when at last, after weeks or months, the long-awaited rain comes, what looked like dead leaves become green again within a few hours as if by magic. The plant can lose up to 95 per cent of its water reserves without being harmed. It enters a deep sleep phase in which it winds down its metabolism almost to zero.

The resurrection plant\'s emergency plan is genetically programmed: a whole series of genes is only used in drought periods, with others being shut down completely. "By looking at which genetic features are mainly active during periods of drought we are attempting to understand which molecular processes make the plant so hardy," Professor Dorothea Bartels of the University of Bonn\'s Botanical Institute explains. In this way her team was able to identify a hereditary feature which is deployed much more frequently during drought than under normal conditions. To their surprise the researchers found a gene which is very similar to that of the resurrection plant\'s in mouse-ear cress, which is indigenous to Germany - \'a really lucky find\', Prof. Bartels adds. The mouse-ear cress (its scientific name is Arabidopsis thaliana) is the plant geneticists\' equivalent of the laboratory mouse, since it is a model organism which is simple to breed and genetically easy to modify, whose genetic pattern has been completely sequenced.

The drought gene ensures that the plant can cope better with specific toxins which increase when the plant is hit by drought stress. It contains the structural plan for the detoxification enzyme aldehyde dehydrogenase (ALDH). The Bonn scientists supplied the ALDH gene of the mouse-ear cress with a kind of turbocharger which ensures that it kicks in considerably more frequently. And it worked: the genetically modified plants not only produced appreciably more ALDH, they also survived substantially longer droughts. Only after 16 days without water were they completely desiccated - their cousins in the wild only survived 12 days without the life-giving water. Even where the salt concentration was higher than normal - a frequent occurrence in the soils of arid regions - the plants with the turbocharger coped better.

On a long-term basis findings like these might contribute towards developing drought-resistant varieties of maize, wheat or soya. There is certainly enough demand: according to a study by the International Water Management Institute, by 2025 one third of the world\'s population will be living in arid regions. Tragically, it is the poorest of the poor who are hardest hit, because they rely on the yields of their fields in order to survive. However, even the industrialised countries are no strangers to this development: in the US half of the entire maize and one third of the soya bean crop were destroyed by the 1983 drought alone. And in view of this year\'s extreme drought German farmers estimate that they could lose up to 80 per cent of their crops.

Contact person:
Professor Dorothea Bartels
Botanical Institute of the University of Bonn
Tel.: ++49-228-732070
Fax: ++49-228-732689
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