Light-induced Synthesis of Anthocyanin in Carrot Cells in Suspension: II EFFECTS OF LIGHT AND 2, 4-D ON INDUCTION AND REDUCTION OF ENZYME ACTIVITIES RELATED TO ANTHOCYANIN SYNTHESIS

Time-courses of light-induced activities of enzymes relatingto anthocyanin formation were studied. Phenylalanine ammonia-lyase(PAL), 4-cumarate CoA ligase (4CL) and cinnamate-4-hydroxylase(C4H) (group 1 enzymes) and chalcone synthase (CHS) and chalcone-flavanoneisomerase (CHFI) (group 2 enzymes), were studied in carrot suspensioncells which were irradiated 5 d after transfer to a 2,4-dichlorophenoxyaceticacid (2,4-D)-free medium in the dark. Time-courses of group1 enzymes showed two peaks (fast and slow) with the slow peakincreasing almost parallel to anthocyanin accumulation. Time-coursesof group 2 enzymes showed one peak corresponding to the slowpeak of group 1. From the inhibitor experiment, the fast peakalso corresponded to the activity of the newly synthesized enzyme.From the initial phase of the time-courses, enzymes belongingto group 1 always induced more rapidly than those of group 2,and their induction was co-operative. However, once anthocyanin synthesis was induced by light, neitheraddition of 2,4-D nor transfer to darkness could prohibit anthocyaninsynthesis completely. Addition of 2,4-D in the dark completelysuppressed anthocyanin synthesis within 1 d and the activityof CHS also disappeared within 1 d. These results are explainedby a previous hypothesis (Takeda, 1988) that 2,4-D induces thestate change of cells. Key words: Anthocyanin, co-ordinate induction, Daucus carota, 2,4-dichlorophenoxyacetic acid, light-triggered