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We analyzed carotenoid composition and the content and expression of genes encoding isoprenoid and carotenoid biosynthetic enzymes in petals and leaves of chrysanthemums. Most of the carotenoids in yellow petals were β,ɛ-carotenoids, lutein and its derivatives, reflecting the high expression levels of lycopene ɛ-cyclase (LCYE). In contrast, the ratio of β,β-carotenoids to total carotenoids in leaves were higher than that of β,ɛ-carotenoids, reflecting the high expression levels of lycopen β-cyclase (LCYB). Petals of the yellow-flowered cultivar Yellow Paragon showed increased accumulation and drastic componential changes of carotenoids as they matured. In petals of the white-flowered cultivar Paragon, carotenoid content was drastically decreased during petal development and became less than the detection limit late in development. Transcript levels of most genes tested increased during petal development in Yellow Paragon. All genes except that for 1-deoxyxylulose 5-phosphate synthase (DXS) showed similar expression patterns in Paragon. Between-cultivar comparison of the expression of these genes in the petals at mid-development showed no distinct differences between petal color. It is possible that the formation of white petal color is due to neither down-regulation nor destruction of the carotenoid biosynthetic pathway. We presume that another factor inhibits carotenoid accumulation in chrysanthemum petals.