Researchers have successfully engineered lettuce and tobacco plants to produce myoglobin, a key animal protein responsible for meat’s red color, savory flavor, and nutritional iron, according to a study published in the journal Frontiers in Plant Science. Led by a team at Imperial College London alongside Kyomei Ltd., the research introduces a potential new method for creating realistic plant-based meat alternatives without relying exclusively on livestock or industrial fermentation vats.
Scientists Engineer Lettuce and Tobacco to Produce Meat Protein
Myoglobin is an abundant molecule found in the heart and skeletal muscle of vertebrates, storing oxygen while delivering heme iron that absorbs more readily than many plant-based iron sources. While companies such as Impossible Foods typically produce similar proteins by inserting genes into bacteria or yeast grown in industrial bioreactors, this latest experiment directly targeted living crops.
Using a Gene Gun to Target Plant Chloroplasts
To incorporate animal genetics into plant cells, the researchers utilized a biolistic particle delivery system, commonly referred to as a “gene gun.” This device fired microscopic metal particles coated with DNA containing pig myoglobin genes directly into the seedlings of tobacco and lettuce plants.
Rather than placing the new genetic material into the plant’s main nuclear DNA, the team directed the genes into the chloroplasts—the cellular structures responsible for converting sunlight into energy via photosynthesis. Because individual plant cells contain numerous chloroplasts with multiple copies of their own circular DNA, this method significantly increases the volume of the target protein a cell can manufacture.
The chloroplast approach vastly outperformed conventional plant engineering techniques. Among 37 plants produced using standard methods, myoglobin accumulation remained at least threefold lower than what the chloroplast approach achieved. The engineered seedlings grew into normal, fertile plants that flowered and successfully passed the transferred pig genes on to their seeds.
Yields, Heme Challenges, and Next Steps
Measurements showed that the mature plants yielded roughly 800 milligrams of myoglobin per kilogram of dry weight in tobacco and 810 milligrams per kilogram in edible lettuce. While these totals remain modest compared to real meat—which typically contains 8,100 to 11,200 milligrams per kilogram—study authors noted that plant cultivation requires far lower water use and produces lower greenhouse gas emissions than livestock production.
However, an important technological hurdle remains. The researchers discovered that only about 35 percent of the plant-produced myoglobin successfully attached its essential iron-carrying heme molecule, compared with roughly 80 percent for myoglobin produced in bacteria. Because heme is necessary to provide meat’s red color and characteristic flavor, a myoglobin protein lacking it is functionally inert.
According to study lead author Alexia Groff, future efforts will focus on boosting the plant’s own heme supply, extracting and purifying the protein using standard industrial methods, and testing additional plant lines. Co-author Dr. Kyoko Morimoto of Kyomei suggested that if the technology gains legislative approval, modified edible lettuce could one day serve as a heme-iron-enriched biofortified food.
