Grow-in-the-dark plants could spark the next Green Revolution
The new Green Revolution might look a little like this: peach orchards heavy with fruit in the middle of January, dense rows of corn flourishing in sandbox-sized plots, and grocers stocking persimmons in the heat of summer.
And it might start with the phytochrome – a crucial light-sensing molecule that tells plants when to germinate, grow, make food, flower and age. Scientists have mapped and manipulated the phytochrome's structure, aiming to alter the conditions under which plants grow and develop. Eventually, they want to insert these modified phytochromes into plants to trick them into growing, and bearing seeds and fruit – even when they're not supposed to.
"We hope to create a toolkit of phytochromes that can eventually be used to control agriculture – how plants grow, when they flower, when they die," said Richard Vierstra, a plant geneticist at the University of Wisconsin-Madison, who described the phytochrome's structure in the June 30 edition of the Proceedings of the National Academy of Sciences. He and his colleagues "want to pack more plants per acre" and even grow seasonal crops year-round – possibly saving space and other resources, as well as increasing food security.
Do you know where your flowers grow?
Sweeter veggies come in from the cold
How to keep your plants alive — with an app
But it might be several more years before phytochrome kits make their way to farmers' hands. Vierstra and his colleagues have only just begun making these mutants and inserting them into the sprightly mustard weed, Arabidopsis thaliana – not into any other plants.
Still, the idea is a tantalizing one. Boosting crop density could help feed a global population set to surge by about 1 billion over the next decade or so. The resulting increase in food demand could require an additional 120 million hectares of agricultural land by 2030 – or a farm the size of South Africa. But drought and desertification might render an area twice that size barren in the meantime. Vierstra's research could help maximize the precious arable land we have left. It "has the potential to provide plants with superior capacity for food and biofuel productivity," said Peter Quail, director of the Plant Gene Expression Center at UC Berkeley.
Phytochromes, like eyes, convert light into chemical signals. "Plants use the molecule to sense… whether they are above, next to or under other plants," Vierstra said. Phytochromes in plants under full sun absorb red light, switching to an active form that tells them to make seeds and fruit, while those shaded by their neighbors sense only the "leftover," far-red light, switching their phytochromes to an inactive form that directs them toward the sun. They grow "more stems instead of making the seeds you want."
That means even though farmers often try to increase crop yield by planting more seeds per acre, they might not harvest much more of the coveted seeds or fruit, Vierstra said. Plants "don't like" cramped conditions. "We have to engineer plants so they do like being grown that way…. There really is a need to re-engineer the phytochrome system."
To that end, he and other UW-Madison researchers set out to determine the structure of a phytochrome from A. thaliana using a 3-D imaging technique called crystallography. For years, scientists believed that the light-sensing part of the phytochrome – known as the chromophore – rested on the molecule's surface, triggering a structural change to an active form when it absorbs light. But crystallography revealed that the chromophore was buried inside the molecule, which Vierstra predicted would result in an entirely different change than had been predicted if the chromophore were on the surface. He needed to know how the phytochrome's structure actually changed in order to manipulate its on/off switch.
To confirm that his model was correct, Vierstra mutated the amino acids thought to be crucial to initiating the change. Sure enough, the phytochromes remained in an active form – even in pitch darkness. The researchers then made various mutant phytochromes, tricking them to stay active for longer or shorter periods of time than normal. Now they're trying to generate a catalog of mutants that they can insert back into A. thaliana plants, and then observe how they behave.
Scientists could even trick phytochromes into ignoring growing seasons. The ratio of active to inactive phytochromes reflects the hours of day and night, indicating the time of year, which, in turn, tells plants when to sprout, flower, fruit or go to seed. But researchers could, for example, insert plants with phytochromes that stay active all year. Take spinach, which grocers don't sell in the summer, when it doesn't grow leaves, only flowers. "We can theoretically grow spinach year-round by changing the flowering signals that come from phytochromes," Vierstra said.
But Vierstra isn't only scientist tackling dwindling agricultural lands. University of Illinois researchers are identifying genes that allow corn to tolerate high densities, while Purdue University researchers have proposed a more out-there solution: growing corn underground. They found that corn thrived in an abandoned limestone mine installed with insulation and heat lamps, where growth conditions were tightly controlled. The natural coolness of mines lessens the need to ventilate the heat generated by lamps, while the high carbon dioxide levels promote plant growth. And the enclosed space could prevent genetically modified pollen and seed from escaping into the ecosystem.
Like Vierstra's research, it sounds so crazy it just might work. But when contending with a swelling population and shrinking arable lands, a no-holds barred approach might be exactly what's needed.
Ozy.com is a Paste BN content partner providing general news, commentary and coverage from around the Web. Its content is produced independently of Paste BN.