Red lettuce gets its color from natural pigments called anthocyanins. These pigments are made inside the plant from an amino acid called phenylalanine.
Scientists used a tool called genome editing to turn off a gene that makes an enzyme named dihydroflavonol 4‑reductase. This enzyme works just before the plant makes anthocyanins. When the gene was switched off, the lettuce stopped producing the red color.
When the red pigment stopped, the plant made more of other flavonoids, such as quercetin. This shows that blocking one pathway can push the plant to build other helpful chemicals.
Plant growth stayed normal
Even though the lettuce looked different and had more flavonoids, it grew just as well as normal lettuce. This means we might be able to change the mix of healthy compounds in lettuce without hurting its yield.
Red lettuce already contains many good polyphenols. By tweaking the genes, growers could create lettuce with a custom mix of nutrients.
Flavonoid levels can change with light and temperature. Because indoor farms can control these conditions, the new method could help make special lettuce varieties for such farms.
This work was funded by the Japan Science and Technology Agency.