Air pollution gets up your noseHow do plants decide when to produce flowers? John Innes Centre scientists on the Norwich Research Park are using a common garden weed to understand the biology that regulates the timing of flower production. They hope their work with thale cress (Arabidopsis thaliana ) will ultimately help plant breeders to develop new seasonally-adapted crop varieties. Plants keep in tune with the passing seasons to control flower production. “Winter” varieties (sown in the autumn) need the low temperatures during winter to trigger flowering when the weather warms up. This is vernalisation. “Spring” varieties don’t need this chilling period, so can be sown in the spring for harvest in late summer. This underlying difference between spring and winter varieties extends the geographical range in which various crops can be grown. So how are spring and winter varieties different? Why don’t spring varieties need vernalising before flowering? Which environmental signals do plants use to decide when to flower? And how do they detect these signals and activate flower production? Conventional cross-breeding has revealed genetic differences between winter and spring crop varieties. And temperature and day length seem to be important environmental signals affecting flowering time. So the challenge is to identify the plant genes that sense changes in temperature or day length and trigger flowering. In crop plants, this is an immense task. On average, plant DNA contains around 80,000 genes, so pinpointing specific ones is extremely difficult. Also, over 50 different genes are thought to be involved in a plant’s decision to flower. So scientists worldwide have turned to thale cress - a garden weed which has proved an ideal “model” for research. It has fewer genes than most other plants, which helps narrow the search for individual genes. Also, thale cress plants are small, so lots can be grown in a limited laboratory space. Best of all, the plant produces flowers within just 6 weeks of sowing. This means the results of cross-pollination experiments are available sooner than in crop plants, which takes several months. Many types of thale cress varieties are similar to some crop varieties in that they need vernalising before they will flower. So the JIC scientists compared the genetic information (DNA) of naturally-occurring spring and winter varieties of thale cress. They found that the need for a vernalisation treatment could be traced to a single gene in the winter variety. Closer investigation showed that all winter varieties tested have an intact version of this gene. But a variety that makes flowers without vernalisation (a “spring” variety) has a mistake in its version of the same gene. When an intact copy of the gene was put into the spring variety, the plant needed vernalising in order to flower. This makes it very likely that the JIC scientists have identified a gene that is crucial in determining seasonal adaptation. Having found this gene in thale cress, they now know what to look
for in important crop species. The aim is to see if control of flowering
in crops such as wheat, barley, sugar beet and brassicas involves
the same gene. As well as opening up the possibility of new crop
species, this work should also give the JIC scientists a better
understanding of how plants sense, and respond to their environment. © Dr Belinda Clarke 2001 This Article originally appeared as part of the "Science on your Doorstep" series, published in the Eastern Daily Press 17th February 2001
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