“I think there’s just a sense of intrinsic excitement about things that glow in the dark,” says Sarkisyan, a synthetic biologist at Imperial College London and one of the engineers behind the petunias. He is also cofounder of the Idaho-based biotech company Light Bio, which this month got permission from the US Department of Agriculture to sell its glowing petunias in the United States. The company is planning to start shipping the plants in early 2024.
The genetically engineered plants produce a neon green hue, thanks to the addition of DNA from a type of bioluminescent mushroom called Neonothopanus nambi. “We’re using a natural system taken from a fungus that is usually found in tropical forests and transferring it to plants,” Sarkisyan says. During the day, N. nambi is an unremarkable brown color. At night, it glows a ghostly green.
There are about 1,500 known bioluminescent species, including bacteria, fish, jellyfish, worms, amphibians, arthropods, and mushrooms. Bioluminescence is produced naturally when oxygen reacts with a substance called luciferin, with the help of an enzyme called luciferase, to produce energy in the form of light. The process is poorly understood in most organisms except bacteria.
In 2018, Sarkisyan was part of an international team of scientists that identified the enzymes in N. nambi that allow it to emit light. Two years later, they described inserting the genes for those enzymes into tobacco plants, which were used because they’re easy to breed and they grow rapidly. The resulting plants gave off green illumination in their leaves, stems, roots, and flowers.
Sarkisyan founded Light Bio with Keith Wood, a chemist who in 1986 was among a group of scientists that created the first genetically engineered glowing plant using a gene from fireflies. The team, from the University of California, San Diego, published their discovery in the journal Science. Though the glow was dim, “it was really a novel thing back then,” Wood says.
But the plants couldn’t glow on their own. Rather, they had to be sprayed with a specialized chemical needed to produce the bioluminescence—luciferin from fireflies.
Decades later, researchers at MIT also produced plants with this chemical by packaging the firefly enzymes into tiny materials called nanoparticles that are used as delivery systems. They suspended the particles in a solution, then submerged the plants in that liquid. It made the plants glow for a few hours. Wood says the idea hasn’t caught on commercially, though, because “people want plants that glow brightly without any unusual treatments or requirements.”
In 2010, scientists at Stony Brook University used genes from bioluminescent marine bacteria to produce a self-glowing plant, but the light it produced was dull. Piggybacking on that discovery, entrepreneur Antony Evans launched a Kickstarter campaign in 2013 to create “glowing plants with no electricity” using a different type of bacteria. Anyone who donated was promised seeds to grow their own glowing plants. The project raised nearly half a million dollars on Kickstarter—and sparked concerns about a potential large-scale release of genetically engineered plants that could become invasive pests.
After years of tinkering, Evans’ company, Taxa Biotechnologies, couldn’t deliver on its promise. It turns out that getting plants to glow on their own was more difficult than it initially seemed. Designing a plant with new features isn’t as simple as adding new genetic parts; those parts must actually integrate within the host. The firefly and bacterial genes just didn’t work well in plants.
Sarkisyan and Wood think they’ve solved that problem. They say the fungal bioluminescence pathway they’ve discovered can be coordinated with the plant’s own metabolic system to produce light. The process involves a molecule called caffeic acid, which is abundant in plants to make cell walls. It’s also present in fungus, where it’s converted into luciferin by four different enzymes. Light Bio’s plant is engineered with the genes that make those enzymes.
They claim the resulting plants glow more brightly than any previous plants. The petunias emit light throughout the plant’s entire life cycle, but the flowers are particularly luminous. “The light lets you see almost into the spiritual core of these plants,” Wood says.
While more than a dozen genetically modified foods are available around the world, only a few ornamental plants have made it to the market, including a blue rose and several hues of purple carnations.
In the US, the government reviews applications from companies wanting to introduce new genetically modified plants or crops. In the case of Light Bio’s petunia, the USDA determined that it was not likely to create pest or disease problems for agriculture compared to regular cultivated petunias and could be safely grown and bred outside of a lab setting.
Jennifer Kuzma, codirector of the Genetic Engineering and Society Center at North Carolina State University, says she’s concerned that the agency didn’t conduct a more formal assessment of the plant’s potential environmental and ecological risks. Even though bioluminescence occurs naturally, glowing plants could affect the behavior of insects and animals that aren’t accustomed to it. “It depends on how widely these are grown and whether they were to establish more wildly,” she says.
In its application to the USDA, Light Bio addressed this concern, saying that petunias are normally grown in people’s homes, businesses, or botanical gardens, where “nighttime illumination due to artificial lighting far exceeds light emission from the auto-luminescent petunias.”
Wood says Light Bio is ramping up commercial production, and customers can now sign up to reserve a plant. More than 10,000 people are already on the waiting list. Wood says the company initially plans to sell the plants online in a limited release next spring before expanding to nurseries and gardening centers. Wood and Sarkisyan want to make more types of ornamental plants, and they are working on making them even brighter.
Drew Endy, an associate professor of bioengineering at Stanford University, has seen some of the company’s early prototypes and is excited that Light Bio has revived the idea of bioluminescent plants. He says the number of people who contributed to the failed Kickstarter project a decade ago shows that there’s interest from the public. “People wished for the whimsical and the sublime, and they wanted to be part of something,” he says.
Critics might wonder what the point of a glowing houseplant is. Endy can imagine utilitarian uses, like as replacements for harsh artificial lighting. (A startup in Paris is genetically engineering what is arguably a more functional houseplant with superior air purification properties.) But he thinks the fact that the plants are just plain cool is a better answer. “They invite people to experience biotechnology from a position of wonder,” he says.
If the company is successful in bringing its product to the market, Endy anticipates a bigger societal discussion about this kind of biotechnology: “What’s it going to be like when your neighbor has glowing petunias in their garden, or when kindergartners are watering their bioluminescent petunias?”