Researchers altered a key step in lettuce pigment production, removing its red coloration while subtly reshaping the plant’s internal chemistry.
Red-leaf lettuce may look like a simple salad ingredient, but its deep color is the result of a complex chemical process that scientists are now learning to control.
This vibrant hue comes from anthocyanins, a group of polyphenolic pigments known for their antioxidant properties. In plants, these compounds are produced through a chain of enzyme-driven reactions that begin with the amino acid phenylalanine.
Red-leaf lettuce is a popular leafy vegetable commonly used in salads and fresh dishes, valued for both its mild flavor and its higher levels of health-related compounds compared to many green varieties. Its red coloration is often associated with increased polyphenol content, making it of particular interest for nutrition and plant science research.
As anthocyanins are formed, several related compounds called flavonoids appear along the way. These molecules act as intermediates in the pathway, linking pigment production to a broader network of plant metabolism.
Genome Editing Alters Pigment Production
In this study, researchers used genome editing to switch off the gene responsible for producing dihydroflavonol 4-reductase. This enzyme plays a key role just before anthocyanins are formed in red lettuce. When the gene was disabled, the plants lost their red color.
Further analysis showed that other flavonoids, including quercetin, accumulated at higher levels. This shift suggests that when anthocyanin production is blocked, the plant redirects its internal chemical processes toward other compounds.
Importantly, the modification did not produce any noticeable negative effects on plant growth. This finding indicates that it may be possible to adjust flavonoid composition by encouraging the buildup of precursor compounds while still maintaining normal development and yield.
Although direct comparisons with green lettuce varieties have not yet been completed, red-leaf lettuce is already known for its high polyphenol production. This approach could provide a new strategy for developing lettuce varieties with targeted nutritional properties.
Environmental Influence and Future Applications
Flavonoid production is strongly influenced by environmental factors such as light intensity and temperature.
These results may help support the development of specialized lettuce grown in controlled environments like plant factories, where conditions can be carefully adjusted to optimize both composition and quality.
Reference: “CRISPR/Cas9-mediated knockout of DFR alters pigmentation and shifts flavonoid accumulation in red leaf lettuce without detectable growth penalties” by Ai Nagamine, Masaki Ono, Osuke Sato, Eiji Goto and Hiroshi Ezura, 18 February 2026, Frontiers in Genome Editing.
DOI: 10.3389/fgeed.2026.1755922
The research in the Ezura group is funded by the following grants: Program on Open Innovation Platform with Enterprises, Research Institute and Academia, Japan Science and Technology Agency (JSTOPERA, JPMJOP1851).
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