Induction of Furano-terpene Production and Formation of the Enzyme System from Mevalonate to Isopentenyl Pyrophosphate in Sweet Potato Root Tissue Injured by Ceratocystis fimbriata and by Toxic Chemicals.

When sweet potato (Ipomoea batatas) root tissue was infected by Ceratocystis fimbriata, activity of the enzyme system from mevalonate to isopentenyl pyrophosphate, especially of pyrophosphomevalonate decarboxylase (EC 4.1.1.33), was increased in the noninfected tissue adjacent to the infected region, preceding the furano-terpene production in the infected region. Cutting and incubation of sweet potato slices did not produce furano-terpenes, and only slightly increased the activity of the enzyme system from mevalonate to isopentenyl pyrophosphate. The enzymic activity in diseased tissue was localized in the soluble fraction, and was higher in the tissue from the surface to a depth of about 5 mm with gradual decrease toward the inner part.Mercuric chloride (0.1%, w/v) and sodium dodecyl sulfate (1.0%, w/v) were utilized as model inducers of furano-terpenes and pyrophosphomevalonate decarboxylase. The mercuric chloride- or sodium dodecyl sulfate-induced response was inhibited by administration of cycloheximide to the discs together with the inducer immediately after disc preparation. When cycloheximide or blasticidin S was applied together with the inducer, to the discs 9 hours or more after disc preparation, the induction was not inhibited but rather stimulated.