In chrysanthemums, the white petal color is dominant over the yellow and is postulated to arise from a single dominant gene that inhibits carotenoid formation. By differential screening, we identified a gene that is expressed specifically in white petals of chrysanthemum. The gene is highly homologous to Arabidopsis carotenoid cleavage dioxygenase 4 and was designated CmCCD4a. Suppression of CmCCD4a expression by RNAi turns the white petal yellow. In addition, all the carotenogenic genes were expressed in white petals. The results indicate that carotenoids are biosynthesized in white petals but are degraded by CmCCD4a, leading to white petal color. Although CmCCD4a has been shown to catalyze the conversion of beta-carotene to beta-ionone in E. coli, its catalytic product in planta has not been identified yet. Whether the mechanism of white petal color formation found in chrysanthemum is applicable to other plant species will be discussed.

Involvement of CCD4 in white petal color formation

243rd National Meeting (2012)

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