Deletion of carotenoid cleavage dioxygenase 4a (CmCCD4a) and global up-regulation of plastid protein-coding genes in a mutant chrysanthemum cultivar producing yellow petals

- Transcriptomes of chrysanthemum cultivars with white or yellow petals were compared.
- CmCCD4a was absent in the genome of the chrysanthemum cultivar with yellow petals.
- Numerous plastid protein-coding genes were up-regulated in the cmCCD4a mutant.

In addition to attracting pollinators and protecting plants from photooxidative damages, carotenoids play important roles in signaling related to plant development and physiological changes through their cleaved derivatives, apocarotenoids. Yellow chrysanthemum flower petals [Chrysanthemum morifolium (Ramat.)] are the result of a deleted or suppressed carotenoid cleavage dioxygenase gene (CmCCD4a). Therefore, investigating the global gene expression patterns in chrysanthemum mutants producing yellow petals represents an appropriate strategy to analyze the effects of signaling mediated by carotenoid derivatives. We compared the transcriptomes of chrysanthemum cultivars producing white petals with purple stripes ('Noble Wine') and its mutant producing yellow petals with purple stripes ('ARTI-Yellow Star'). Read mapping and polymerase chain reaction analysis revealed that CmCCD4a is absent in the ARTI-Yellow Star genome, while at least three CmCCD4a gene family members are actively transcribed in 'Noble Wine' plants. These results indicate that the deletion of CmCCD4a may be responsible for the development of yellow petals in ARTI-Yellow Star flowers. During comparisons of gene expression patterns between Noble Wine and ARTI-Yellow Star, we detected numerous significantly up-regulated plastid protein-coding genes as well as significantly or mildly up-regulated carotenoid biosynthesis genes in ARTI-Yellow Star plants. The up-regulated plastid protein-coding genes belong to a broad range of functional categories related to translation, photosynthesis, reactive oxygen species scavenging, oxidative phosphorylation, transcription, processing, terpenoid metabolism, and chlorophyll metabolism. Our results present a possible relationship between CmCCD4a and regulation of plastid protein-coding genes.