Light-enhanced caffeic acid derivatives biosynthesis in hairy root cultures of Echinacea purpurea

Light plays an important role in almost all plant developmental processes and provides the fundamental building blocks for growth, development, primary and secondary metabolism. The effects of light on growth rate and caffeic acid derivative (CADs) biosynthesis in hairy root cultures of Echinacea purpurea (Moench) were assessed. Light-grown hairy roots accumulated increased levels of anthocyanins, which became visible in outer cell layer of the cortex as a ring of purple color. The light-grown root cultures also had radially thickened morphology compared with the dark-grown controls. The growth rate and cell viability of the hairy root cultures in light did not show obvious difference in comparison with those in dark. However, biosynthesis of CADs including cichoric acid, caftaric acid, chlorogenic acid and caffeic acid was significantly increased in hairy root cultures grown in the light. The enhanced accumulation of CADs and anthocyanins in E. purpurea hairy root cultures was correlated to an observed light-stimulated activity of phenylalanine ammonium lyase (PAL).