Cloning and Expression of cDNAs for Biosynthesis of Very-long-chain Fatty Acids, the Precursors for Cuticular Wax Formation, in Carnation (Dianthus caryophyllus L.) Petals

Abstract

The cuticle, composed of cutin and associated waxes, probably acts as a barrier against water evaporation from the epidermal surface of flower petals. Cuticle formation begins with the biosynthesis of very-long-chain fatty acids (VLCFAs), catalyzed by a fatty acid elongase complex in epidermal cells. In the present study, cDNAs were cloned and analyzed for three enzymes (DcKCR1, DcHCD1, and DcECR1). Combined with the previously obtained cDNA for DcKCS1, the present study completes the identification of cDNAs for the fatty acid elongase complex in ‘Light Pink Barbara’ carnation for the first time. DcKCS1 transcripts were accumulated at flower opening stage (Os) 2 through Os 6 (full opening stage) with slight changes, but decreased markedly at senescence stage (Ss) 2 and Ss 4. Also, transcripts for DcKCR1, DcHCD1, and DcECR1 were present in considerable amounts during flower opening stages from Os 2 to Os 6. These findings suggested that the expressions of four genes are active during flower opening stage, which is concomitant with the expansion growth in petals requiring rapid formation of a waxy cuticle. Cut flowers of ‘Miracle Rouge’ carnation have an extremely long vase-life of about three weeks. The cuticle layer on the epidermal cells of ‘Miracle Rouge’ petals was thinner than that of ‘Light Pink Barbara’ petals, and ‘Miracle Rouge’ flowers had a depressed expression of DcKCS1, DcKCR1, and DcHCD1 in petals. These findings suggested that the prolonged vase-life of ‘Miracle Rouge’ flowers is not related to cuticle formation.