MOLECULAR-CLONING AND EXPRESSION ANALYSIS OF DIHYDROFLAVONOL 4-REDUCTASE GENE IN FLOWER ORGANS OF FORSYTHIA X INTERMEDIA

The expression, during flower development, of the gene encoding the an thocyanin pathway key enzyme dihydroflavonol 4-reductase (DFR) was inv estigated in floral organs of Forsythia x intermedia cv. 'Spring Glory '. Full-length DFR and partial chalcone synthase (CHS) cDNAs, the gene of interest and a flavonoid pathway control gene respectively, were o btained from petal RNA by reverse transcription PCR. Whereas for CHS n orthern blot analysis enabled the study of its expression pattern, com petitive PCR assays were necessary to quantify DFR mRNA levels in wild -type plants and in petals of 2 transgenic clones containing a CaMV 35 S promoter-driven DFR gene of Antirrhinum majus. Results indicated a p eak of CHS and DFR transcript levels in petals at the very early stage s of anthesis, and different expression patterns in anthers and sepals . In comparison to wild-type plants, transformants showed a more inten se anthocyanin pigmentation of some vegetative organs, and a dramatic increase in DFR transcript concentration and enzymatic activity in pet als. However, petals of transformed plants did not accumulate any anth ocyanins. These results indicate that other genes and/or regulatory fa ctors should be considered responsible for the lack of anthocyanin pro duction in Forsythia petals.