抄録
The red pigments, anthocyanins and betacyanins have never been demonstrated to occur together in the same plant. Although anthocyanins are widely distributed as flower and fruit pigments in higher plants, betacyanins have replaced anthocyanins in the Caryophyllales. Anthocyanins have not been reported to occur in these betacyanin-producing plants, and the evolutionary gain and loss of the two pigments remain a mystery, as do the molecular bases underlying their mutual exclusion. The accumulation of flavonols in the Caryophyllales suggests that the step (s) of anthocyanin biosynthesis from dihydroflavonols to anthocyanins could be blocked in the Caryophyllales. Some insights can be gained from DFR and ANS, which are involved in the biosynthetic pathway from dihydroflavonols to anthocyanins. The cDNAs encoding DFR and ANS were isolated from Spinacia oleracea and Phytolacca americana, plants that belong to the Caryophyllales. The experiments using recombinant DFR and ANS expressed in Escherichia coli revealed that the Caryophyllales plants posses functional DFR and ANS. The expression profiles showed that DFR and ANS were not expressed in most tissues and organs expect seed in S. oleracea. These result indicated that the suppression or limited expression of the DFR and ANS may cause the luck of anthocyanin in the Caryophyllales.
