Isolation of a Leucoanthocyanidin Dioxygenase (LDOX) Gene from a Spray-type Chrysanthemum (Dendranthema x grandiflorum) and Its Colored Mutants

A full-length cDNA and genomic DNA of a leucoanthocyanidin dioxygenase (DgLDOX) gene was isolated from the petals of chrysanthemum 'Argus', and comparative features of the gene among three flower color mutants derived from a gamma-ray mutagenesis were characterized. The cDNA coding region of the gene was 1068 bp and was translated into 356 amino acids accordingly. The genomic DNA size was 1346 bp for 'Argus', while three mutants revealed ranges of 1363 to 1374 bp. A single intron between two coding exons for the DgLDOX gene was found, of which size was 112 bp for 'Argus', but 128 or 137 bp for three flower color mutants, indicating that a genomic insertion in the intron occurred during the gamma-ray mutagenesis. DNA blot analysis revealed the DgLDOX gene presenting as a single copy in the chrysanthemum genome. The DgLDOX gene was expressed in both 'Argus' of light-pink color and two purple color mutants (AM1 and AM3) but had very weak expression in only white color mutant (AM2). The results demonstrated that variations in the flower color of the mutants might be associated with changes in the amino acid moieties in the coding exons or fragment insertions in the intron of the DgLDOX gene, which potentially resulted in less expression of the gene in the white colored mutant.