INHIBITION OF POTATO (SOLANUM-TUBEROSUM) SPROUT GROWTH BY THE MONOTERPENE S-CARVONE - REDUCTION OF 3-HYDROXY-3-METHYLGLUTARYL COENZYME A REDUCTASE-ACTIVITY WITHOUT EFFECT ON ITS MESSENGER-RNA LEVEL

The effect of the monoterpene S-carvone on potato (Solanum tuberosum cv. Bintje) sprout growth was studied in a semi in vivo system using potato eye pieces. S-carvone inhibited sprout growth within 2 days. An extensive loss of the activity of 3-hydroxy-3-methylglutaryl Coenzyme A reductase (HMGR, E.C. 1.1.1.34), a key-enzyme in the mevalonate pathway, occurred concomitantly with the inhibition of sprout growth. The enzyme activity decreased to less than 3 % of the control after 4 days of treatment. The loss of HMGR activity could not be attributed to a direct effect of S-carvone on the enzyme nor to an effect on in vitro translation processes. Northern analysis of the mRNA population at various time intervals during the treatment, using a specific HMGR potato probe, revealed a considerable hybridization signal after 4 days of treatment. This indicated that the effect of S-carvone on the activity of HMGR in potato sprouts is not regulated by transcriptional events, but by as yet unknown mechanisms.