Earth is illuminated by bioluminescence but, for many of us, seeing the natural phenomenon is a rare treat: Catching the glow of a firefly or witnessing a dolphin gliding through electric-blue waters is a thrill.
Researchers are currently manufacturing glowing flowers and ornamental plants that can cast a green aura onto our living rooms. Eyeballing a plant's health via its glow can be a way to quickly measure its health, and the side-effect is anybody who wants a healthy glowing plant in their living room can have one.
A study published Monday in Nature Biotechnology demonstrates that this goal is well on its way to being a reality.
The study authors announce they’ve created a method that causes plants to glow much brighter, and for a longer period of time, than previous efforts. Plants tweaked by this method should be available for purchase within a few years.
The research was conducted through a collaboration between three scientific institutions and Planta, a biotech startup in Moscow. Light Bio is the company that hopes to sell these plants in partnership with Planta; it’s led by a scientist named Keith Wood who, 30 years ago, created the first luminescent plant using a gene from fireflies.
The issues with previous glowing plant experiments, however, were that these plants were very expensive to modify, and their glow didn’t last for long. Previously, scientists focused on inserting luciferin into plants via nanoparticles. Luciferins are chemicals that, when they oxidize with enzymes, emit a light. For many bioluminescent creatures, like jellyfish and sea stars, luciferin underlies the chemical reaction that allows them to glow.
But a discovery made in 2018 in conjunction with bioluminescent fungi allowed scientists to change their approach. When this team examined the Neonothopanus nambi, a poisonous mushroom, they discovered that a molecule called caffeic acid is responsible for its bioluminescence.
During a metabolic cycle involving four key enzymes, caffeic acid is converted into a “luminescent precursor,” oxidized, produces a photon, and then converted back into caffeic acid. The byproduct of this process is that the fungi emit light.
In this new study, the team harnessed that information and inserted those four enzymes — which are specific to the mushroom — into the DNA of tobacco plants. In turn, the enzymes were able to interact with the caffeic acid in the tobacco plants, and cause them to globe both in the dark and in the daylight. When it’s not involved with bioluminescence, caffeic acid helps strengthen cell walls and is involved in driving the colors and fragrances of plants.
This method, the scientists claim, made the plants 10 times brighter than previous efforts and the sustained light production didn’t harm the health of the plants. The plants in this study can produce over a billion photons per minute.
The team recorded the green glow with just regular cameras and smartphones — the light emitting from stems, roots, flowers, and leaves.
Interestingly, the luminescence decreased as the leaves aged — but it also increased when the leaves were damaged. In turn, the team suggests this method could also help other researchers monitor plant responses to various stressors and changes in the environment. If a drought, or a hungry herbivore, is harming a plant, bioluminescence could warn of this damage before it’s too late.
The team hopes to create even brighter plants in the future, and reports they are currently experimenting with glowing periwinkles, petunias, and roses.
Abstract: Autoluminescent plants engineered to express a bacterial bioluminescence gene cluster in plastids have not been widely adopted because of low light output. We engineered tobacco plants with a fungal bioluminescence system that converts caffeic acid (present in all plants) into luciferin and report self-sustained luminescence that is visible to the naked eye. Our findings could underpin the development of a suite of imaging tools for plants.