Carotenoids and apocarotenoids are essential for biological functions in plants, animals and humans. Different apocarotenoids are produced from cleavage of carotenoids at specific bond positions by the family of carotenoid cleavage dioxygenases (CCDs). The plant CCD4 enzymes have been reported to be expressed in flower tissues and preferentially cleave linear carotenoids. We hypothesized that CCD4 may be the gene that controls the flower color phenotype (white versus yellow) in Brassica (fast plant). Our results indicated that white flower color is dominant over yellow in petals of fast plants and is controlled by a single gene. qRT-PCR analysis showed much high expression of CCD4b in white flower compared to yellow flowers. Nucleotide sequences of CCD4a and CCD4b from fast plants were 99% identical and the genes are intron-less. The predicted amino acid sequences of CCD4 contained ~600 aa with chloroplast signal peptide in their N-terminus as well as several conserved histidine residues. Functional complementation of CCD4a and CCD4b in E.coli revealed significant [beta]-carotene degradation and [beta]-ionone release from cell extracts expressing both white and yellow CCD4b. Partial or low [beta]-carotene cleavage was observed in E.coli harboring the CCD4a constructs. However, the carotenoid level and [beta]-ionone release could not explain the petal color phenotype when analyzed through HPLC and GC-MS. Further experiments on molecular genetics (e.g. linkage analysis) may conclude the biological role of CCD4 in controlling petal color. i