The pentacyclic biosynthetic precursor of jasmonic acid, 12-oxo-phytodienoic acid, was found to induce synthesis of the major flavonoid, apiin. in cell suspension cultures of Petroselinum crispum. The accumulation of apiin was preceded by an increase in the relative levels of poly (A)* RNAs that code for the flavonoid biosynthetic enzymes phenylalanine ammonia lyase, 4-coumarate:CoA ligase and chalcone synthase, Poly (A)* RNAs reached maximal levels at approximately 4–6 h after the addition of elicitor while flavonoids continued to accumulate in the cultures for at least 6 days. 12-Oxo-phytodienoic acid is the first pentacyclic precursor in the jasmonic acid biosynthetic chain which functions as a signal transducer for phytoalexin induction.
