Gene discovery may aid in development of drought-tolerant crops

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Parts of the Southeastern U.S (where I live) have been experiencing severe drought conditions for months. Droughts can have significant environmental and economic impacts on a community.

According to this press release, aridity is on the increase across the globe, as is the world population, and it is important that increasingly dry areas should be taken into cultivation to ensure food production.

Researchers from the University of Helsinki and the University of California in San Diego have discovered a plant gene that could help in the development of drought-tolerant crops.

Here's a little background information:

It has been proposed that guard cell anion channels function as important regulators of stomatal closure (stomata are tiny pores on the plant leaf surface) and are essential in mediating stomatal responses to physiological and stress stimuli. However, the genes encoding membrane proteins that mediate guard cell anion efflux have, until this study, not been identified.

Stomatal pores, formed by two surrounding guard cells in the epidermis of plant leaves, allow influx of atmospheric carbon dioxide in exchange for transpirational water loss. Stomata also restrict the entry of ozone - an important air pollutant that has an increasingly negative impact on crop yields, and thus global carbon fixation and climate change. The aperture of stomatal pores is regulated by the transport of osmotically active ions and metabolites across guard cell membranes. Despite the vital role of guard cells in controlling plant water loss, ozone sensitivity and carbon dioxide supply, the genes encoding some of the main regulators of stomatal movements remain unknown.

Overview of the experimental process:
1.During a screen for plant mutants sensitive to ozone, they identified a gene called SLAC1 (slow anion channel-associated 1) that appeared to be insensitive to increased ozone and carbon dioxide levels. In other words, this plant mutant did not react to high ozone or carbon dioxide concentrations by closing its stomata like a normal plant.

2.They found that the SLAC1 protein was essential for stomatal closure in response to environmental and physiological stresses because when they put normal SLAC1 back into the mutant plants they now functioned like normal plants.

3.However, SLAC1 mutants appeared to be similar to normal plants in other ways:
a.They had similar number of stomata
b.They had similar gene expression patterns

4.The researchers then hypothesized that these differences must be due to stomatal malfunction.

5.On further examination of the SLAC1 gene they determined that it encoded a predicted membrane protein.

6.They expressed a version of SLAC1 fused to a green fluorescent protein (GFP) and showed that it localized to the plasma membrane of guard cells.

7.Finally, they showed that SLAC1 is part of an S-type anion channel because mutations in SLAC1 only impaired S-type anion channel currents but did not affect other types of channels.

So, why is it important that they identified an anion channel involved in stomatal function?

The regulation of stomata is an intensively-studied topic and several ion channel types that control their activity have been discovered earlier. However, this is the first time an anion channel, which is of central importance in the regulation of stomatal activity has been discovered.

Research like this that addresses the mechanisms by which plants evaporate moisture will be central to developing new species of drought-resistant plants.

The research findings are available on Nature's Advance Online Publication site.
Image credit: Brian Fuchs, National Drought Mitigation Center
Excerpts taken from Vahisalu et al., 2008

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Just curious, do you think that modifying plants in this fashion is a good idea? I'm very ambivalent about the issue. On the one hand, plants that would survive tougher climate conditions would be nice, especially considering that the climate is likely to get more unpredictable in the coming years. However, a monoculture would be very susceptible if the wrong plant virus/fungi/bacteria happened by. Crop dynamics are very interesting.

The drought problem in Georgia is partly due to rainfall, and partly due to the hodgepodge of local, state and federal water rights usage laws. Of course, if you live here you know this already (remember Sunny's prayer for rain on the capitol steps?).

Off topic: I'm in Emory GMB, are you in BCDB? How close to finished, can you see the light at the end of the tunnel yet?

Hi Eric,
You are right that cultivating large areas with plants that lack genetic diversity would make them more susceptible to mass destruction from a single element.

I think farmers would have to use a combination of different drought tolerating methods including the use of various (genetically diverse) drought-tolerating species. Other drought-tolerant target genes that have been identified include the ERA1 gene, for example.

Yes, I'm in BCDB and yes I can see a light at the end of the tunnel-I'm aiming for this summer and actively seeking a job :)

You have a nice blog. Are you aware of the newly formed Science Writers Association of Emory (SWAE)? Maybe I'll see you around.
Take care

By Karen Ventii (not verified) on 18 Mar 2008 #permalink