Isolation of genes determining the flower color traits in Asiatic hybrid lily and their characterization by RNAi

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Because anthocyanin pigmentation in tepals of Asiatic hybrid lily is controlled by a single dominant gene and anthocyanin biosynthetic genes are expressed coordinately in tepals, some transcription factor is expected to control the presence or absence of anthocyanin pigment. In this study, two genes, LhbHLH1 and LhbHLH2 were isolated, which had homologies with PhJAF13 and PhAN1, respectively. LhbHLH1 and LhbHLH2 were expressed in tepals and leaves. When lily buds were exposed to light, anthocyanin pigment accumulated in leaves, which nearly disappeared 8 days after light exposure. Expression of LhbHLH2 was strongly affected by light, which peaked at 2 days after light exposure and decreased after that. This expressional change was nearly parallel with the change of anthocyanin content. Similar result was observed in tepals, that is, both anthocyanin content and LhbHLH2 expression were decreased by the dark treatment. These results suggest that the two bHLH genes, especially LhbHLH2, ar … More e correlating to anthocyanin biosynthesis. Next, carotenoid composition and the expression of genes encoding carotenoid biosynthetic enzymes were analyzed. Most of the carotenoids in yellow petals were antheraxanthin, 9Z-violaxanthin, cis-lutein and violaxanthin, and the major carotenoid in red petal was capsantin. Tepals of yellow and red flowered cultivars showed increased accumulation of carotenoids, whereas carotenoid content was decreased in those of white and pink flowered cultivars. Carotenoid biosynthesizing genes, PSY, PDS, ZDS, CRTISO, LCYB, HYB and LCYE, were isolated and their expression was examined. Transcription of PSY, PDS, ZDS, CRTISO, and HYB increased as tepals grew and peaked at the 6-7 cm tepal-length stage. On the contrary, transcription of LCYB and LCYE were constant and decreased, respectively, during tepal development. Transcription patterns of these genes were basically the same among yellow, red, pink and white colored tepals although carotenoid contents were very different among them, indicating that carotenoid accumulation in tepals is not explained by the transcription of biosynthetic genes. Less