Red-leaf lettuce is red owing to anthocyanins, a class of polyphenolic pigments widely studied for their antioxidant properties. In plants, anthocyanins are synthesized through enzymatic reactions originating from the amino acid phenylalanine. Along this biosynthetic pathway, multiple flavonoids—an umbrella term for diverse plant secondary metabolites—are produced as intermediates and ultimately converted into anthocyanins.
In this study, the researchers used genome editing to inactivate the gene encoding dihydroflavonol 4-reductase, which catalyzes a key step immediately upstream of anthocyanin production in red lettuce. Disruption of this gene eliminated red pigmentation. Metabolite analyses also revealed increased accumulation of other flavonoids, including quercetin, indicating a redirection of metabolic flux within the flavonoid biosynthesis pathway.
Notably, no significant negative effects on lettuce growth were observed following this genetic modification, highlighting the potential to control flavonoid composition by favoring precursor accumulation rather than anthocyanin production while maintaining normal growth and yield. Although direct comparisons with green lettuce cultivars remain to be performed, red lettuce is known to exhibit high polyphenol biosynthetic activity. Therefore, the researchers’ approach represents a promising strategy for developing lettuce cultivars with tailored functional components. Moreover, because flavonoid biosynthesis is strongly influenced by environmental factors such as light intensity and temperature, these findings may support the establishment of functional lettuce varieties optimized for plant factories, where growth conditions can be precisely controlled.
Read the paper: Frontiers in Genome Editing
Article source: University of Tsukuba via EurekAlert
Image: Genome-edited lettuce (right) in which the genes involved in flavonoid biosynthesis in the original red-leaf lettuce variety (left) were modified, resulting in green leaves and altered flavonoid composition. Credit: University of Tsukuba
