Two key enzyme genes associated with ethylene bio-synthesis, LbACS and LbACO, are involved in the regulation of lily flower senescence

Ethylene plays an important role in regulating the growth and development of flowers and determines the flower life span of ornamental plants. In this study, the lily variety 'Manissa' was used to elucidate the mechanism associated with the regulation of lily senescence by the genes for 1-aminocyclopropane-1-carboxylic acid synthetase (ACS) and 1-aminocyclopropane-1-carboxylic acid oxidase (ACO), which are key enzymes in the ethylene biosynthesis pathway. The results showed that ethylene release increased, the relative water content first increased and then decreased, and relative conductivity continuously increased as lily bud development progressed. LbACS1 transcription was highest at the blooming stage, LbACS7 transcription was highest at the green bud stage, and LbAC03 and LbAC04 levels both peaked at the yellow bud stage and the blooming stage. After treating cut lily flowers with ethephon and ethylene inhibitor 1-methylcyclopropene (1-MCP), the results showed that ethephon promoted the senescence of cut flowers, ethylene release, and the transcription levels of the four Lb genes. 1-MCP treatment also delayed the aging of cut flowers, but reduced ethylene release and inhibited the transcription of LbAC03 and LbAC04 when the treatment was applied during the later stages of bud development. This study provided evidence for the role of ethylene and the functions of LbACS and LbAC0 in the aging process associated with cut lily flowers.