Induction of two prenyltransferases for the accumulation of coumarin phytoalexins in elicitor-treated Ammi majus cell suspension cultures

Abstract

Two dimethylallyl diphosphate: umbelliferone dimethylallyltransferase (prenyltransferase) activities, catalysing the 6-prenylation and the 7- O-prenylation, respectively, of umbelliferone in the course of phytoalexin synthesis, increased in Ammi majus cell suspension cultures in response to elicitor treatment. Both enzyme activities were dependent on Mg 2+ or Mn 2+ with significant preference for Mg 2+ in the 6-prenylation reaction. Whereas darkgrown cells did not contain these activities, both prenyltransferase activities were induced rapidly by the addition of elicitor reaching a first maximum after 10–14 hr and a second maximum beyond 30 hr. Other coumarin specific, elicitor-induced enzyme activities of A. majus cells, in contrast, showed only one maximum of activity within the 50 hr experimental period, while the pattern of induction of phenylalanine ammonia-lyase activity resembled that of the prenyltransferases with maxima at ca 8 hr and 20–30 hr. Preliminary data suggest that the apparent biphasic induction of these enzyme activities is due to post-translational enzyme modifications.