Abstract:A flowering regulated transcription factor SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) homologous gene, NtSOC1, was cloned from the flower bud of Narcissus tazetta var. chinensis using RTPCR and rapid amplification of cDNA ends. NtSOC1 is 1 603 bp in length with an open reading frame 687 bp which is capable of encoding 228 amino acids. Phylogenetic analysis indicated that the amino acid sequence of NtSOC1 is similar with the SOC1s in other species, especially the SOC1 in monocots. NtSOC1 contains a highly conservative SOC1 motif, which indicates that NtSOC1 belongs to the SOC1/TM3 subfamily gene. Fluorescence quantitative PCR analysis showed that the expression level of NtSOC1 in flower bud differentiation stage increased with the differentiation of flower bud and decreased at the end of flower bud differentiation, which indicated that NtSOC1 might be involved in flower bud differentiation of narcissus. The pCAMBIA1302NtSOC1 expression vector was successfully constructed. Recombinant plasmid was introduced into onion epidermal cells by Agrobacterium tumefaciens method. Subcellular localization result showed that the NtSOC1 was localized in the nucleus, which was consistent with the general character of subcellular localization of transcription factors. The results laid a foundation for further study of the function of NtSOC1 gene.