Molecular characterization of the flavonoid biosynthetic pathway and flower color modification of Nierembergia sp
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<i>Nierembergia</i> sp., a popular floricultural species, only has violet and white flower color and lacks pink to red. To elucidate the reason, we analyzed its flavonoids. Its major anthocyanin was determined to be delphinidin 3-<i>O</i>-(6-<i>O</i>-(4-<i>O</i>-(4-<i>O</i>-(6-<i>O</i>-caffeoyl-β-D-glucopyranosyl)-<i>p</i>-coumaroyl)-α-L-rhamnosyl)-β-D-glucopyranosyl)-5-<i>O</i>-β-D-glucopyranoside. The petals rarely contained cyanidin and pelargonidin, and they contained more flavonols than anthocyanins. We also characterized the biosynthetic pathway by cloning the cDNAs encoding enzymes involved in the flavonoid biosynthesis pathway: chalcone synthase (CHS), flavanone 3-hydroxylase (F3H), flavonoid 3′-hydroxylase (F3′H), flavonoid 3′,5′-hydroxylase (F3′5′H), dihydroflavonol 4-reductase (DFR), flavonol synthase (FLS), and UDP-rhamnose: anthocyanidin 3-glucoside rhamnosyltransferase (3RT). Northern blot analysis revealed that the expressions of <i>CHS</i>, <i>F3′5′H</i>, <i>DFR</i>, and <i>3RT</i> genes were coordinately regulated in parallel with anthocyanin accumulation in the petals, indicating that anthocyanin biosynthesis is transcriptionally regulated; on the other hand, the transcripts of the <i>F3′H</i> gene were rarely detected. Antisense suppression of the <i>F3′5′H</i> gene decreased the amount of <i>F3′5′H</i> transcripts and that of delphinidin. It was noteworthy that the color of the transgenic flower changed from violet to white rather than to reddish, which was the expectation.
- Plant tissue culture letters
Plant tissue culture letters 23(1), 19-24, 2006-03-01
Japanese Society for Plant Cell and Molecular Biology