Expression of CCD4 gene involved in carotenoid degradation in yellow-flowered Petunia × hybrida

Abstract Petunia is a popular commercial bedding plant that comes in many colors, but there are no petunia cultivars with deep yellow petals. The carotenoid degradation gene carotenoid cleavage dioxygenase (CCD4) was isolated from white and yellow-flowered petunia and we found the 226-bp insertion of a non-autonomous transposable element tourist-like miniature-inverted repeat (MITE) in the coding region of CCD4 only in yellow cultivars. The insertion interrupts gene expression because of a premature stop codon after the TE insertion and could form secondary structures in hairpin RNA that could then be processed into a mature miRNA. Here, the normal function of CCD4 isolated from a white cultivar was introduced to a yellow cultivar. The transformants showed more fading pale-yellow flowers and carotenoid content was decreased. These results indicate that transformed CCD4 expression promoted carotenoid degradation and the lack of CCD4 expression results in more carotenoid accumulation in wild-type yellow-flowered petunia.