Carotenoid composition and changes in expression of carotenoid biosynthetic genes in tepals of Asiatic hybrid lily

To elucidate the regulatory mechanisms of carotenoid accumulation in tepals of Asiatic hybrid lily (Lilium spp.), the content and composition of carotenoids and transcriptional changes of carotenoid biosynthetic genes were compared between tepals of yellow, red, pink and white flowers. Yellow and red tepal cultivars accumulated high amounts of carotenoids, and cultivars with pink and white tepals accumulated small amounts of carotenoids. Most of the carotenoids in yellow petals were antheraxanthin, (9Z)-violaxanthin, cis-lutein and violaxanthin. Capsanthin was accumulated in red tepals. Transcription of phytoene synthase, phytoene desaturase, zeta-carotene desaturase, carotenoid isomerase and beta-ring hydroxylase in tepals increased as tepals grew. Among yellow and red tepal cultivars, the amounts of carotenoids were well associated with the transcription levels of biosynthetic genes, indicating that transcription levels regulate carotenoid accumulation in these cultivars. However, in pink and white tepals, the transcription levels of biosynthetic genes were similar to those in red tepals, indicating that small amounts of carotenoids are not explained by down-regulation of biosynthetic genes. Another factor should reduce carotenoid amounts in these tepals.