Induction and repression of phenylalanine ammonia‐lyase and chalcone synthase enzyme proteins and mRNAs in carrot cell suspension cultures regulated by 2,4‐D

Abstract

Changes in the amounts of enzyme proteins and mRNAs for phenylalanine ammonia‐lyase (PAL, EC 4.3.1.5) and chalcone synthase (CHS, EC 6.‐.‐.‐) were investigated in suspension cultures of carrot (Daucus carola L. cv. Kurodagosun), in which anthocyanin synthesis was induced and repressed in the absence and presence of 2,4‐dichrolophenoxyaeetic acid (2,4‐D), respectively. The amounts of enzyme proteins were measured using anti‐PAL and anti‐CHS sera. In a medium lacking 2,4‐D, enzyme proteins and mRNAs for both PAL and CHS were induced 5 days after transfer, when the anthocyanin synthesis was induced. They all increased coordinately during days 5‐7 after transfer, when anthocyanin was rapidly synthesized, and then they decreased. In contrast, in a medium containing 2,4‐D, the amount of enzyme protein and mRNA for CHS were below detectable levels throughout the culture time. As regards PAL, however, whether 2,4‐D was present or not, both enzyme protein and mRNA rapidly increased after the transfer of cells to fresh medium, and then decreased and remained at low levels in a medium containing 2,4‐D. The addition of 2,4‐D to cells cultured for 6 days in a medium lacking 2,4‐D caused an immediate decrease in the amounts of enzyme proteins and mRNAs for both PAL and CHS.All the results obtained here indicate that the induction and suppression of the synthesis of PAL and CHS were probably due lo increase and decrease, respectively, in the amounts of their mRNAs. Thus, it is suggested that the induction and suppression of anthocyanin in this system may be regulated at the transcriptional level by 2,4‐D.