Auronidins are a previously unreported class of flavonoid pigments that challenges when anthocyanin biosynthesis evolved in plants

Significance Anthocyanins are flavonoid plant pigments that may be important for coping with environmental stresses, such as high light, drought, and nutrient deprivation. It has been thought that anthocyanin biosynthesis arose when land plants evolved approximately 450 million y ago, and extant basal plants groups, such as liverworts, have been reported to have “primitive” anthocyanins bound to their cell walls. However, here we report that the red pigments of the liverwort Marchantia are not anthocyanins, but rather a unique class of phenylpropanoids, for which we propose the name “auronidins.” Auronidins have similar colors as anthocyanins but distinct biosynthesis and color properties, and they may contribute to the remarkable ability of liverwort to survive in extreme environments.