Abstract
A gene encoding carotenoid cleavage dioxygenase (CmCCD4a) is specifically expressed in white chrysanthemum (Chrysanthemum morifolium Ramat.) petals and brings about white coloration via the cleavage of carotenoids (Ohmiya et al., 2006). In order to obtain a stable promoter that induces exogenous gene expression specifically in the petals, we isolated and characterized the CmCCD4a promoter. We obtained approximately 3 kb upstream of CmCCD4a by using the TAIL-PCR method. A transient expression assay performed using the particle bombardment transformation system revealed that the 1.2-kb region sufficiently mimicked the promoter activity and that 2 cis-regions, designated cis1 and cis2, were involved in ray petal-specific expression. In addition, we found that chimeric promoters containing a combination of cis1/2 and the 1.2-kb CmCCD4a promoter enhanced both promoter activity and the organ specificity of the original CmCCD4a promoter. We are now growing transformed chrysanthemums harboring chimeric CmCCD4a promoter constructs fused to the beta-glucuronidase (GUS) reporter gene.
