Bio-Engineered Plant to Shine Bright

The glowing greenhouse theory is now perhaps a reality that ever before with scientists having genetically engineered a plant with both visible and self-sustaining glow that’ll last till the end of the plant’s life cycle.
It is visibly brighter and longer than previously engineered tobacco glowing plants and doesn’t require constant chemical maintenance in order to preserve its glow.

The notion of ‘Avatar’ based lighting may still be out of hand though but the glowing greenery would most certainly help us understand the plants responds to the world around them.
Two specific tobacco plant species were selected and experimented on and unlike previous glowing plants, which was based on bioluminescent bacteria or firefly DNA, these plants were engineered using the DNA of bioluminescent fungi.

“Although bacterial bioluminescence genes can be targeted to plastids to engineer autoluminescence, it is technically cumbersome and fails to produce sufficient light,” the researchers wrote in their paper.
“The caffeic acid cycle, which is a metabolic pathway responsible for luminescence in fungi, was recently characterised. We report light emission in Nicotiana tabacum and Nicotiana benthamiana plants without the addition of any exogenous substrate by engineering fungal bioluminescence genes into the plant nuclear genome.”

Source: ScienceAlert.com

It was in 2018 that a research paper was published on the biosynthesis of fungal luciferin, a compound that produces a glow in luminescent fungi.

According to Science Alert, the fungi synthesise luciferin from a compound called caffeic acid, worked upon by four enzymes. Two enzymes work to transform caffeic acid into a luminescent precursor; a third enzyme oxidises this precursor to produce a photon. The fourth enzyme then converts the molecule back to caffeic acid, which can be recycled through the same process.
The caffeic acid found in all plants, which is key to the biosynthesis of lignin, the wood polymer that gives plant cell walls rigidity and strength.

The scientists, therefore, surmised it could be possible to genetically engineer plants to reallocate some of their caffeic acid to the biosynthesis of luciferin, as seen in bioluminescent fungi.
The tobacco plant was initially spliced with four fungus genes associated with bioluminescence, and carefully cultivated them. Subsequently, the plants glowed with a radiant light visible to the naked eye when matured.
“The overall phenotype, chlorophyll and carotenoid content, flowering time and seed germination did not differ from wild-type tobacco in the greenhouse, with the exception of a 12 percent increase in median height of transgenic plants,” the researchers wrote in their paper.

“This suggests that, unlike the expression of bacterial bioluminescence, expression of caffeic acid cycle is not toxic in plants and does not impose an obvious burden on plant growth, at least in the greenhouse.”
Younger parts of the plants were mostly visible with the flowers being the brightest of all. These produced around a billion photons per minute according to the researchers.

Despite it being about 10 times brighter than the previous experiments, the researchers said. It’s not the brightest plant produced; that honour belongs to watercress produced by scientists at MIT using a technique called plant nanobionics, which produced a glow of around a trillion photons per second… but it only lasted 3.5 hours.
This long-term, self-sustaining glow could act as an indicator of how the plant responds to their external environment.

“By enabling autonomous light emission, dynamic processes in plants can be monitored, including development and pathogenesis, responses to environmental conditions and effects of chemical treatment,” the researchers wrote in their paper.

“By removing the need for exogenous addition of luciferin or other substrates, these luminescent capabilities should be particularly useful for experiments with plants grown in the soil.”
The team in the meantime is working on expanding the research. They have genetically modified popular flowering plants such as periwinkles, petunias, and roses. They are also trying to produce an even brighter glow and different colours.

“Although caffeic acid is not native to animals, autonomous luminescence could also be enabled in animals,” they wrote.

The research has been published in Nature Biotechnology.