Regulation of anthocyanin biosynthesis in UV-A-irradiated cell cultures of carrot and in organs of intact carrot plants.

Two cell lines of Daucus carota are known to differ with respect to anthocyanin accumulation. cDNA clones encoding enzymes involved in anthocyanidin biosynthesis, namely phenylalanine ammonia-lyase (PAL; EC 4.3.1.5), chalcone synthase (CHS; EC 2.3.1.74), flavanone 3-hydroxylase (F3H; EC 1.14.11.9), dihydroflavonol 4-reductase (DFR; EC 1.1.1.219) and leucoanthocyanidin dioxygenase (LDOX; EC 1.14.11.-), were isolated from libraries derived from cell cultures. Northern blot analysis of anthocyanin-accumulating (DCb) and non-accumulating (DCs) cell cultures of carrot showed that the anthocyanin pathway in these anthocyanin-free DCs cells is blocked. The expression of CHS1, DFR1 and LDOX is not detectable. However, F3H and DFR2 behave differently. In the European wild carrot (Daucus carota ssp. carota) the structural genes coding for the enzymes responsible for anthocyanin biosynthesis are strongly expressed in organs which accumulate anthocyanins. Only the dark-purple coloured petals of the central flowers of the inflorescence and to a certain extent the white flowers and the leaves but not the stems and the roots transcribe these genes. To study the effect of anthocyanins as UV-screens the expression of a protein indispensable for cell proliferation like alpha-tubulin (TUB) was monitored.