FLAVONOID BIOSYNTHESIS IN FLOWER PETALS OF 5 LINES OF LISIANTHUS (EUSTOMA-GRANDIFLORUM GRISE)

The biosynthesis of flavonoid pigments during petal development was in vestigated in five lines of lisianthus (Eustoma grandiflorum Grise.), with purple, pink, mauve or white flowers (W42 and W84). Flavonols wer e found at high levels at all stages of petal development, but peaked just prior to flower opening. In the cyanic lines, anthocyanins were f irst detected in opening flowers, increasing in amounts thereafter. Th e polymerase chain reaction was used to generate cDNAs from lisianthus petal RNA for phenylalanine ammonia-lyase (PAL), chalcone synthase (C HS), chalcone isomerase (CHI) and dihydroflavonol 4-reductase (DFR), a nd expression of their corresponding mRNAs during petal development in vestigated. In the cyanic lines, PAL, CHS and CHI transcripts were pre sent throughout petal development, with peak expression in young, acya nic buds. DFR expression was low in young buds and peaked immediately preceding anthocyanin synthesis. Thus, the activity of the biosyntheti c genes correlated closely with the flavonoid content of the petals, w ith the synthesis of flavonols being temporally separated from that of anthocyanins. Transcripts for all four genes examined were detected i n both white-flowered lines, although line W42 had only low levels for DFR. Neither white-flowered line could synthesize anthocyanins when p etal tissue was fed with leucopelargonidin and leucocyanidin (fed to W 42 only), products of the DFR enzyme. Thus, line W42 may lack activity for a regulatory factor that controls the expression of the genes of the later part of the flavonoid biosynthetic pathway, while W84 may co ntain a block in the conversion of leucoanthocyanidin to anthocyanin.