Abstract:

ACC oxidase（ACO）is a key enzyme in the biosynthesis pathway of ethylene. In order to
explore the characteristics and function of the ACO gene in narcissus，the following work has been done in
this study. Petals of Narcissus tazetta var.‘Yunxiang’were used as experimental materials，a full-length
1 162 bp sequence was obtained by RT-PCR and named as NtACO1（GenBank KX082935）. The open
reading frame（ORF）length of NtACO1 is 939 bp，which encodes 312 amino acids. Amino acid domain
analysis showed that this gene has DIOX_N and 20G-FeⅡ_Oxy domains and was identified as a member
of the ACO protein family. Molecular phylogenetic tree analysis showed that ACO gene of‘Yunxiang’was
closely related to that of Narcissus tazetta var. chinensis. qRT-PCR results showed that the expression of
NtACO1 increased gradually with Narcissus flower development and senescence，and the expression level
in the petals were higher than that in contemporaneous coronas，indicating that the NtACO1 gene may be involved in the flower development and senescence of‘Yunxiang’. We obtained several NtACO1
overexpression transgenic tobacco plants using the Agrobacterium mediated. Compared with wild type，the
vegetative growth stage of transgenic tobaccos was reduced，as well as the transgenic tobaccos showed
early flowering and less leaves. This study lays an experimental foundation for further research on the
function of ACO gene and provide a theoretical basis for the molecular breeding in prolonging plant
florescence of Narcissus.

Key words: Narcissus, gene clone, genetic engineering, prolonged flowering, ACC oxidase