REGULATION OF ANTHOCYANIN BIOSYNTHESIS IN CELL-SUSPENSION CULTURES OFVITIS IN RELATION TO CELL-DIVISION

Cell suspension cultures of Vitis produce anthocyanin in the dark afte r cessation of cell division. Production of anthocyanin was associated with increasing activities of phenylalanine ammonia-lyase (PAL) and c halcone synthase (CHS) which followed transcript amounts. The level of endogenous phenylalanine, a precursor of anthocyanin, was also elevat ed before anthocyanin accumulated. Addition of phosphate to the medium at the early stationary phase induced cell division and completely in hibited the biosynthesis of anthocyanin. Activities of PAL and CHS did not increase in the stationary phase when phosphate was again added t o the medium. The amount of phenylalanine decreased significantly afte r addition of phosphate. In contrast, when cells were inoculated into medium lacking phosphate, accumulation of anthocyanin was detected on day 2 and activities of PAL and CHS increased. The level of endogenous phenylalanine reached a maximum just before the initiation of anthocy anin synthesis. When phenylalanine was added to the medium in mid-loga rithmic phase when the phenylalanine pool was lowest, the level of phe nylalanine was immediately elevated and accumulation of anthocyanin wa s initiated. Enzymatic activity of CHS also increased by the addition of phenylalanine. Transcript level increased synchronously with change s in the amount of phenylalanine, after its addition. We conclude that the induction of anthocyanin biosynthesis in cell suspension cultures of Vitis is triggered by high levels of endogenous phenylalanine foll owing the cessation of cell division. Under these conditions, phenylal anine may be a signal that promotes transcription of genes of the anth ocyanin biosynthetic pathway.