The biochemical and molecular investigation of flower color and scent sheds lights on further genetic modification of ornamental traits in Clivia miniata

Clivia miniata is renowned for its evergreen and strap-like leaves, whereas its floral color and scent are lacking diversity. Here, anthocyanin, volatile terpene, and carotenoid metabolisms were integrally investigated in C. miniata flowers. The results showed that pelargonidins and lutein might cooperate to confer orange or yellow color to C. miniata flowers, but only a trace amount of (+)-limonene was detected. The expression levels of CmF3'H and CmDFR appeared to be responsible for the ratio of cyanidin and pelargonidin derivatives in C. miniata, and the low expression of CmF3'H was responsible for the lack of cyanidins in flowers. Moreover, the CmF3'H promoter could not be activated by CmMYBAs, suggesting that it was controlled by novel regulators. Only two CmTPSs were functional, with CmTPS2 responsible for (+)-limonene synthesis, contributing to the monotonous flower volatile terpenes of C. miniata. CmCCD1a and CmCCD1b were able to cleave carotenoids at the 5,6 (5',6'), and 9,10 (9',10') positions to generate volatile apocarotenoids, whereas the substrates found in low-quantities or specific subcellular localizations of CmCCD1s might constrain volatile apocarotenoid release. Consequently, activating F3'H and introducing novel F'5'H or versatile TPS may be effective ways to modify the floral color and scent, respectively. Alternatively, modifying the carotenoid flux or CCD1 localization might affect floral color and scent simultaneously. Taking these results together, the present study provides a preliminary deciphering of the genetic constraints underlying flower color and scent development, and proposes possible schemes for further genetic modification of ornamental traits in C. miniata and other plants.