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Interviewee: Julian Schroeder,
A Don’t-Waste-Water Gene
Sleep with your jaw hanging open, and you’ll wake up to a dry mouth. Plant biologist Julian Schroeder says that when plants keep open the tiny breathing holes on the undersurface of their leaves, they experience a similar phenomenon. Without rain to replenish the lost water, plants wither and perish.
Now, Schroeder and an international team of researchers from Finland, Estonia, the United Kingdom, and the US have discovered a gene, called SLAC1, that helps plants shut their microscopic leaf pores and therefore conserve water. For certain plants, the gene kicks into gear under drought conditions, so it’s a potential target for researchers looking to design more drought-resistant plants.
“The $64 billion question,” says Schroeder, “is can you use this gene as one of the toolbox of genes that we need to engineer improved drought tolerance in plants? And we’re very excited that now in our research, we can analyze this kind of question and move forward now that we have the gene in hand.”
If he and colleagues can use the SLAC1 gene to engineer heartier plants, you might be able to scratch off “water the lawn” from your chore list. But the goals of drought resistance engineering go very far beyond backyard gardening.
The staggering effects of this year’s global food shortages make the project of drought tolerance engineering particularly pressing.
“If a plant could survive a week or ten days longer through a prolonged drought, that could mean a big difference in yield to a farmer,” Schroeder says. “In the dry regions of the world, over 80 to 90 percent of fresh water is used for agriculture. We need to use that water because the people of the world need to grow food to eat,” he says.
Further research may illuminate which plants already have the SLAC1 gene and whether it can be triggered.
An Open-and-Shut Case
Plant breathing pores, also known as stoma, consist of two special cells called guard cells. Over a decade ago, Schroeder’s team discovered a protein that lets electrical charges flow in and out of the guard cells, causing them to inflate and open the pore, or deflate and close the pore. That provided a clue that this protein could be important to how plants save water during drought.
Finding the protein was an important step, but Schroeder says it’s taken years to find the SLAC1 gene that encodes that protein. “Before you have found the gene, you don’t really have the ultimate proof of the theory. Now that we found the gene, we can say for sure it is responsible for the drought stress response of the plants,” he says.
As he and colleagues described in the journal Nature, they tested the function of SLAC1 by shutting it off in some plants and seeing how the mutant plants fared under drought conditions. In plants that lacked the functioning gene, the breathing pores tended to remain open. “Because they do not close, the plant loses much more water through the leaf breathing pores during drought stress,” says Schroeder. That’s bad news for those experimental plants, but provides evidence that the gene is crucial for effective guard cell functioning.
“These breathing pores in the leaves are the major pathway through which plants lose water. They lose over ninety percent of their water by evaporation through the breathing pores,” Schroeder says. Keeping these breathing pores shut, then, is a major goal of future drought-resistance engineering.
“We’re living in a world today with six billion people, projected to grow to over eight billion people. And we require increasing amounts of fresh water for life, to grow crops, to grow the foods that we need, and to produce oxygen,” says Schroeder. Taking shorter showers is one way for us to save water. Now, with the discovery of the SLAC1 gene, we may be able to teach plants some water conservation tricks of their own.
This research was published in the journal Nature and funded by the Academy of Finland Centre of Excellence, Helsinki University Environmental Research Centre, Estonian Science Foundation, University of Tartu, NIH, NSF, DOE, and the Leverhulme Trust.
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