Publications

• Yellow flowers generated by expression of the aurone biosynthetic pathway.

  Ono E., Fukuchi-Mizutani M., Nakamura N., Fukui Y., Yonekura-Sakakibara K., Yamaguchi M., Nakayama T., Tanaka T., Kusumi T., Tanaka Y.

  Flower color is most often conferred by colored flavonoid pigments. Aurone flavonoids confer a bright yellow color on flowers such as snapdragon (Antirrhinum majus) and dahlia (Dahlia variabilis). A. majus aureusidin synthase (AmAS1) was identified as the key enzyme that catalyzes aurone biosynthe ... >> More

  Flower color is most often conferred by colored flavonoid pigments. Aurone flavonoids confer a bright yellow color on flowers such as snapdragon (Antirrhinum majus) and dahlia (Dahlia variabilis). A. majus aureusidin synthase (AmAS1) was identified as the key enzyme that catalyzes aurone biosynthesis from chalcones, but transgenic flowers overexpressing AmAS1 gene failed to produce aurones. Here, we report that chalcone 4'-O-glucosyltransferase (4'CGT) is essential for aurone biosynthesis and yellow coloration in vivo. Coexpression of the Am4'CGT and AmAS1 genes was sufficient for the accumulation of aureusidin 6-O-glucoside in transgenic flowers (Torenia hybrida). Furthermore, their coexpression combined with down-regulation of anthocyanin biosynthesis by RNA interference (RNAi) resulted in yellow flowers. An Am4'CGT-GFP chimeric protein localized in the cytoplasm, whereas the AmAS1(N1-60)-RFP chimeric protein was localized to the vacuole. We therefore conclude that chalcones are 4'-O-glucosylated in the cytoplasm, their 4'-O-glucosides transported to the vacuole, and therein enzymatically converted to aurone 6-O-glucosides. This metabolic pathway is unique among the known examples of flavonoid, including anthocyanin biosynthesis because, for all other compounds, the carbon backbone is completed before transport to the vacuole. Our findings herein not only demonstrate the biochemical basis of aurone biosynthesis but also open the way to engineering yellow flowers for major ornamental species lacking this color variant. << Less

  Proc. Natl. Acad. Sci. U.S.A. 103:11075-11080(2006) [PubMed] [EuropePMC]

  This publication is cited by 4 other entries.

• Specificity analysis and mechanism of aurone synthesis catalyzed by aureusidin synthase, a polyphenol oxidase homolog responsible for flower coloration.

  Nakayama T., Sato T., Fukui Y., Yonekura-Sakakibara K., Hayashi H., Tanaka Y., Kusumi T., Nishino T.

  Aureusidin synthase, which plays a key role in the yellow coloration of snapdragon flowers, is a homolog of plant polyphenol oxidase (PPO). The enzyme specifically acted on chalcones with a 4-monohydroxy or 3,4-dihydroxy B-ring to produce aurones, for whose production the oxidative cyclization of ... >> More

  Aureusidin synthase, which plays a key role in the yellow coloration of snapdragon flowers, is a homolog of plant polyphenol oxidase (PPO). The enzyme specifically acted on chalcones with a 4-monohydroxy or 3,4-dihydroxy B-ring to produce aurones, for whose production the oxidative cyclization of chalcones must be preceded by 3-oxygenation. However, it exhibited virtually no PPO activity toward non-chalcone phenolics. The enzyme was competitively inhibited by phenylthiourea, a specific PPO inhibitor. These results led us to propose a mechanism of aurone synthesis by aureusidin synthase on the basis of known PPO-catalyzed reactions and conclude that the enzyme is a chalcone-specific PPO specialized for aurone biosynthesis. << Less

  FEBS Lett. 499:107-111(2001) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Enzymatic formation of aurones in the extracts of yellow snapdragon flowers.

  Sato T., Nakayama T., Kikuchi S., Fukui Y., Yonekura-Sakakibara K., Ueda T., Nishino T., Tanaka Y., Kusumi T.

  The yellow coloration of snapdragon (Antirrhinum majus) flowers is mainly provided by the 6-glucosides of aureusidin and bracteatin. However, the biochemical mechanism of aurone biosynthesis is not well understood. In this study, we have identified aurone-biosynthesizing activity in the extracts o ... >> More

  The yellow coloration of snapdragon (Antirrhinum majus) flowers is mainly provided by the 6-glucosides of aureusidin and bracteatin. However, the biochemical mechanism of aurone biosynthesis is not well understood. In this study, we have identified aurone-biosynthesizing activity in the extracts of yellow snapdragon flowers. Incubation of 2',4',6',4-tetrahydroxychalcone (THC) with an enzyme preparation in the presence of H(2)O(2) caused the enzymatic formation of a single product, aureusidin, without the formation of a previously proposed 2-(alpha-hydroxybenzyl)coumaranone intermediate. The formation of aureusidin from THC was specifically observed with yellow flowers as well as aurone-accumulating flowers of other colors. The pH optimum for the enzymatic formation of aureusidin was around 5.4. Stoichiometric studies showed that one mole of aureusidin formation was accompanied by the consumption of one mole of oxygen with no detectable consumption of H(2)O(2), which may work as an enzyme activator. The oxidative formation of aureusidin from THC could be explained in terms of the action of a single enzyme, an internal monooxygenase catalyzing the 3-hydroxylation and oxidative cyclization of THC. Incubation of 2',4',6',3,4-pentahydroxychalcone (PHC) with an enzyme yielded both aureusidin and bracteatin at an approximate molar ratio of 6:1. In this case, H(2)O(2) was not required for enzyme activity but rather inhibited the reaction. The 4'-glucosides of THC and PHC could also act as substrates for the formation of the 6-glucosides of aurones. These results suggest that aureusidin can be produced from either THC or PHC, whereas bracteatin is not produced through the 5'-hydroxylation of aureusidin but arise solely from PHC. << Less

  Plant Sci 160:229-236(2001) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Aureusidin synthase: a polyphenol oxidase homolog responsible for flower coloration.

  Nakayama T., Yonekura-Sakakibara K., Sato T., Kikuchi S., Fukui Y., Fukuchi-Mizutani M., Ueda T., Nakao M., Tanaka Y., Kusumi T., Nishino T.

  Aurones are plant flavonoids that provide yellow color to the flowers of some popular ornamental plants, such as snapdragon and cosmos. In this study, we have identified an enzyme responsible for the synthesis of aurone from chalcones in the yellow snapdragon flower. The enzyme (aureusidin synthas ... >> More

  Aurones are plant flavonoids that provide yellow color to the flowers of some popular ornamental plants, such as snapdragon and cosmos. In this study, we have identified an enzyme responsible for the synthesis of aurone from chalcones in the yellow snapdragon flower. The enzyme (aureusidin synthase) is a 39-kilodalton, copper-containing glycoprotein catalyzing the hydroxylation and/or oxidative cyclization of the precursor chalcones, 2',4',6',4-tetrahydroxychalcone and 2',4',6',3,4-pentahydroxychalcone. The complementary DNA encoding aureusidin synthase is expressed in the petals of aurone-containing varieties. DNA sequence analysis revealed that aureusidin synthase belongs to the plant polyphenol oxidase family, providing an unequivocal example of the function of the polyphenol oxidase homolog in plants, i.e., flower coloration. << Less

  Science 290:1163-1166(2000) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.