Grow-in-the-Dark Plants Could Spark the Next Green Revolution
WHY YOU SHOULD CARE
Because researchers want to feed a booming population by tricking plants into ignoring space constraints and even seasons.
The new Green Revolution might look a little like this: peach orchards heavy with fruit in mid-January, dense rows of corn flourishing in sandbox-sized plots and grocers stocking persimmons in the heat of summer.
We hope to create a toolkit of phytochromes that can eventually be used to control … how plants grow…
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. Now they hope to insert these modified phytochromes into plants to trick them into growing and bearing 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 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.
It might be several more years before phytochrome kits make their way into farmers’ hands. Vierstra and his colleagues have only just begun making these mutants and inserting them into the sprightly mustard weed Arabidopsis thaliana, and not yet into any other plants.
Still, the idea is tantalizing. 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 — a farm the size of South Africa — while drought and desertification might render an area twice that size barren in the meantime. Vierstra’s research could help maximize the 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. Under full sun, phytochromes absorb red light, which prompts them to switch to an active form that in turn tells them to make seeds and fruit. Plants shaded by neighbors sense only the “leftover,” far-red light; their phytochromes switch to an inactive form that grows “more stems instead of making the seeds you want.”
Plants don’t like cramped conditions. Manipulating phytochromes is about engineering them so they do.
That’s why farmers often fail to increase yields by planting more seeds per acre. They might not harvest more coveted seeds or fruit, Vierstra said. Plants just don’t like cramped conditions. Manipulating phytochromes is really about “engineer[ing] plants so they do like being grown that way.”
We can theoretically grow spinach year-round by changing the flowering signals that come from phytochromes.
To manipulate the phytochrome’s on/off switch, Vierstra and other UW-Madison researchers first needed to know its structure. They used a 3-D imaging technique called crystallography to map a phytochrome from A. thaliana. What they found surprised them. Scientists had long believed that the light-sensing part of the phytochrome, the chromophore, rested on the molecule’s surface. But crystallography revealed that the chromophore was buried inside the molecule. That suggested that the activation process relied on different amino acids than originally thought.
To confirm that hypothesis, Vierstra mutated the amino acids thought to be crucial to activation. When he did, 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 proportion of light to dark hours, indicating the time of year, which, in turn, tells plants when to sprout, flower, fruit or go to seed. In the summer, for instance, spinach grows only flowers, not leaves. But with mutant phytochromes that stay active all year, “We can theoretically grow spinach year-round by changing the flowering signals that come from phytochromes,” Vierstra said.
Vierstra isn’t the 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. The natural coolness of mines lessened the need to ventilate the heat generated by lamps, while the high carbon dioxide levels promoted plant growth. And an 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.