INHIBITION AND REGULATION OF SHIKONIN BIOSYNTHESIS IN SUSPENSION-CULTURES OF LITHOSPERMUM

The accumulation of acetylshikonin, p-hydroxybenzoic acid-O-glucoside (PHB-Glc) and rosmarinic acid (RA) was investigated in cell suspension cultures of Lithospermum erythrorhizon under the influence of blue an d white light, of in vivo inhibitors of 3-hydroxy-3-methylglutaryl-coe nzyme A reductase (HMG-CoA reductase) and phenylalanine ammonia lyase (PAL), and of the effecters methyl jasmonate and arsenate. The activit ies of p-hydroxybenzoate geranyltransferase, p-hydroxybenzoate O-gluco syltransferase and HMG-CoA reductase were assayed. 2-Aminoindan-2-phos phonic acid, an inhibitor of PAL, completely suppressed the formation of acetylshikonin, PHB-Glc and RA. Mevinolin, an inhibitor of HMG-CoA reductase specifically blocked the formation of acetylshikonin, thereb y increasing the formation of PHB-Glc. The activity of p-hydroxybenzoa te-O-glucosyltransferase was not regulated by the intracellular concen tration of p-hydroxybenzoate, but directly by light. White light rathe r than blue light induced the activity of this glucosyltransferase, wh ereas PHB geranyltransferase activity was repressed by blue light. The activity of HMG-CoA reductase correlated with the production of acety lshikonin, This suggests a regulatory role for HMG-CoA reductase in th e isoprenoid part of shikonin biosynthesis.