COUMARINS AND OTHER PHENYLPROPANOID COMPOUNDS IN THE DEFENSE RESPONSE OF PLANT-CELLS

Cultured cells of the Apiaceae, e.g. Petroselinum crispum and Ammi majus, produce large quantities of coumarin phytoalexins upon treatment with fungal elicitors and concomitantly reinforce their cell walls by ferulic ester incorporation. In these reactions, the cells mimic the disease resistance response commonly expressed in plants following infection by phytopathogenic fungi. Both coumarins and ferulic esters are derived from the general phenylpropanoid pathway. The elicited Apiaceae cell cultures have therefore served as model systems for the investigation of the biosynthetic and regulatory mechanisms involved in phenylpropanoid accumulation. The results of these studies suggest an unconventional pathway for umbelliferone biosynthesis and demonstrate both the transcriptional and post-transcriptional control of a novel pathway to feruloyl-CoA. They underline the enormous contribution of such model systems to the present knowledge on regulatory patterns and DNA coding in secondary metabolism.