Red leaf lettuce lost its signature colour in a new genome editing study, but it kept growing and started building up other plant compounds instead.
Researchers at the University of Tsukuba used genome editing to switch off the gene responsible for producing dihydroflavonol 4-reductase, an enzyme involved in a key step just before anthocyanins are formed in red lettuce.
Anthocyanins are the polyphenol pigments behind the red colour of red leaf lettuce. They are produced through a series of enzyme-driven reactions that begin with the amino acid phenylalanine. The pathway also generates a range of flavonoids before some are eventually converted into anthocyanins.
After the gene was disabled, the plants no longer produced their characteristic red pigmentation.
Further analysis showed that levels of several other flavonoids increased, including quercetin.
The researchers said the findings suggest that blocking anthocyanin production redirected the plant’s biochemical activity toward the buildup of other compounds within the flavonoid biosynthesis pathway.
Despite the shift in pigment and flavonoid composition, the modified lettuce showed no meaningful reduction in growth.
The researchers said that suggests it may be possible to alter the balance of flavonoids in lettuce by encouraging the accumulation of precursor compounds instead of anthocyanins, while maintaining normal growth and productivity.
They said red lettuce is already known for its high level of polyphenol production, although they have not yet directly compared the modified plants with conventional green lettuce varieties.
The team also said flavonoid production is highly sensitive to environmental conditions, including light intensity and temperature.
Because plant factories allow growers to carefully control those factors, the findings may help support the development of specialized lettuce varieties for indoor cultivation systems.
The study, “CRISPR/Cas9-mediated knockout of DFR alters pigmentation and shifts flavonoid accumulation in red leaf lettuce without detectable growth penalties,” was published in Frontiers in Genome Editing.
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