Published online 26 November 2007 | Nature | doi:10.1038/news.2007.289

Genetically modified tobacco doesn't bite the dust.

Heidi Ledford

Researchers have created drought-resistant tobacco plants, which can
withstand prolonged dry periods and thrive on 70% less water than
ordinary tobacco plants.

The finding could be important for creating other drought-resistant
crops, says Jeffrey Leung, a plant biologist at France's National
Centre for Scientific Research in Gif-sur-Yvette, who was not
affiliated with the study.

Thus far, the researchers — led by plant biologist Eduardo Blumwald
of the University of California, Davis — have focused on tobacco,
which is easy to genetically manipulate. They are now trying the same
approach in tomatoes, rice and wheat.

Drought is the major culprit behind crop losses worldwide, and water
shortages are expected to become still more important as climate
change alters rainfall patterns and increases the proportion of arid
land in some key agricultural regions (see Return of the dust bowl?).
In many parts of the world, water is already as expensive as
fertilizer, says Blumwald.

As absent-minded gardeners know all too well, water-starved plants
often cope with the stress by wilting and shedding their leaves.
That’s believed to be a key part of their survival strategy: they
sacrifice older leaves to stay alive just long enough to make seeds.

That approach may boost long-term survival in the wild, but it can be
devastating to crop yields, says Blumwald. “Crops adopt the same
strategy that those plants in the wild use,” he says. “If things go
wrong, they put out some seeds and die. But we do not grow crops for
that.”
A tale of two hormones

In looking at the issue, Blumwald suspected that the drought-induced
leaf shedding was genetically programmed, and reasoned that one way
to circumvent that programming would be to boost a plant hormone
called cytokinin. Cytokinins promote cell division and are found in
actively growing plant tissues. Dying tissues, on the other hand, do
not make the hormone.

So Blumwald and his colleagues created transgenic tobacco plants that
produce a protein that makes cytokinin in stressed tissues. Although
ordinary tobacco plants shed their leaves and died if not watered for
two weeks, the transgenic plants kept their foliage and revived when
watering resumed.

The transgenic plants also suffered only a 12% reduction in yield
when watered with 70% less water than normally used. The findings are
published this week in Proceedings of the National Academy of
Sciences of the USA 1.

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References
1. Rivero, R.M. et al. Proc. Natl Acad. Sci. USA 104,
19631-19636 (2007).