ELICITOR INDUCTION OF FURANOCOUMARIN BIOSYNTHETIC-PATHWAY IN CELL-CULTURES OF RUTA-GRAVEOLENS

Treatment with an autoclaved culture homogenate of the yeast Rhodotoru la rubra induces rapid accumulation of acridone epoxides, furoquinolin es and furanocoumarins in cell cultures of Ruta graveolens (L). The in creased accumulation is preceeded by an induction of enzymes of the bi osynthetic pathways. In the case of furanocoumarins induction was show n for phenylalanine ammonia-lyase (PAL), 4-coumarate: CoA ligase (4-CL ) and S-adenosyl-L-methionine: xanthotoxol O-methyltransferase (XOMT). For PAL and 4-CL time courses of induced activity showed an early max imum, 8-12 h after treatment, whereas XOMT was found to reach its maxi mum later, about 36-42 h after treatment. The elicitor dose-response c urve showed saturation at an elicitor concentration of 1%. At any time during the whole culturing period cells responded to elicitiation but the maximum enzyme activities induced were lower at the late stages. Experiments with different suspension culture strains, a shoot teratom a culture and hydrcponically grown sterile photomixotrophic plants wer e performed to assess the influence of differentiation on constitutive activities of these enzymes and their inducibility by elicitation. Co nstitutive furanocoumarin accumulation was positively correlated with the level of differentiation. Although induction of PAL, 4-CL and XOMT activity always accompanied induced furanocoumarin accumulation no ab solute correlation existed between induced enzyme activities and the i nduced product level or relative product increase.