An international team of scientists has genetically engineered tobacco plants (Nicotiana tabacum) with a fungal bioluminescence system. This biological light can be used by scientists for observing the inner workings of plants as well as for practical aesthetic purposes, most notably for creating glowing flowers and other ornamental plants.
Glowing young tobacco plants (Nicotiana tabacum). Image credit: Planta.
“Designing new biological features is more complex than merely moving genetic parts from one organism to another. Like gears in a watch, the newly added parts must metabolically integrate within the host,” explained senior co-author Dr. Ilia Yampolsky and colleagues.
“For most organisms, the parts needed for bioluminescence are not all known. Until recently, a complete part list was available only for bacterial bioluminescence.”
“But past attempts to create glowing plants from these parts have not gone well, largely because bacterial parts typically do not work properly in more complex organisms.”
In 2018, Dr. Yampolsky and co-authors uncovered the parts that sustain bioluminescence in Neonothopanus nambi, a species of poisonous and bioluminescent mushroom.
In this new study, the researchers demonstrated that the fungal bioluminescence works particularly well in tobacco plants. This allowed them to make glowing plants that are at least ten-fold brighter.
“Although fungi are not closely related to plants, their light emission centers on an organic molecule that is also needed in plants for making cell walls. This molecule, called caffeic acid, produces light through a metabolic cycle involving four enzymes,” they explained.
“Two enzymes convert the caffeic acid into a luminescent precursor, which is then oxidized by a third enzyme to produce a photon. The last enzyme converts the oxidized molecule back to caffeic acid to start the cycle again.”
“In plants, caffeic acid is a building block of lignin, which helps provide mechanical strength to the cell walls. It is thus part of the lignocellulose biomass of plants, which is the most abundant renewable resource on Earth.”
“By connecting light production to this pivotal molecule, the glow emitted by the plants provides an internal metabolic indicator.”
“It can reveal the physiological status of the plants and their responses to the environment. For instance, the glow increases dramatically when a ripe banana skin is placed nearby (which emits ethylene).”
“Younger parts of the plants tend to glow most brightly and the flowers are particularly luminous.”
“Flickering patterns or waves of light are often visible, revealing active behaviors within the plants that normally would be hidden.”
The team’s paper was published in the journal Nature Biotechnology.
_____
T. Mitiouchkina et al. Plants with genetically encoded autoluminescence. Nat Biotechnol, published online April 27, 2020; doi: 10.1038/s41587-020-0500-9
