The red color of lettuce comes from anthocyanins, a group of polyphenol pigments that have attracted attention for their antioxidant properties. Plants produce anthocyanins through a series of enzymatic reactions that begin with the amino acid phenylalanine. Along the way, the pathway generates a variety of flavonoids, a broad class of plant compounds that serve many functions before some of them are eventually converted into anthocyanins.
In the new study, the researchers used genome editing to turn off the gene responsible for the production of dihydroflavonol 4-reductase, an enzyme involved in a critical step before anthocyanin formation in red lettuce. Once this gene is inactivated, the plants no longer produce their distinctive red pigment.
Further analysis of lettuce revealed another important change. Levels of several other flavonoids, including quercetin, increased. The results indicate that blocking anthocyanin production redirected the plant’s biochemical activity toward the accumulation of these other compounds within the flavonoid biosynthesis pathway.
There is no significant effect on plant growth
Despite significant changes in pigment and flavonoid composition, the modified lettuce showed no significant growth reduction. This result suggests that it may be possible to alter the balance of flavonoids in lettuce by promoting the accumulation of precursor compounds rather than anthocyanins, while maintaining normal growth and productivity.
Although researchers have not yet made a direct comparison between the modified plants and traditional green lettuce varieties, red lettuce is already known for its high level of polyphenol production. As a result, this strategy could offer a promising way to develop lettuce cultivars with tailored functional components.
The researchers also noted that flavonoid production is highly sensitive to environmental conditions, including light intensity and temperature. Because plant factories allow growers to precisely control these factors, the findings may help support the development of specialty lettuce varieties optimized for indoor growing systems.
Research in the Ezura group is funded by the following grants: Open Innovation Platform Program with Companies and the Institute for Research and Academia, Japan Science and Technology Agency (JSTOPERA, JPMJOP1851).
