Abstract: A R2R3-MYB-like gene，named NtMYB5，was selected from transcriptome of Narcissus tazetta var. chinensis and was cloned in order to study its function in flavonoid metabolic pathway. Multiple alignments showed that NtMYB5 contained R2-domain and R3-domain. A pdLNLD/ELxiG/S motif was also found near the C-terminal. Phylogenetic tree analysis indicated that NtMYB5 was closely related to negative regulators of anthocyain biosynthesis. The expression level of NtMYB5 was higher in perianth and corona，and increased during the process of flowering. The accumulation of anthocyanin activated by StMYB was suppressed by NtMYB5 in the transient expression of tobacco. Transgenic tobacco plants were obtained and the flower colour of transgenic plants became lighter. The results of quantitative real-time PCR indicated that most structural genes involved in the anthocyanin pathway were down-regulated by NtMYB5. This study suggests that NtMYB5 is a repressor of anthocyanin biosynthesis in Chinese narcissus.

Key words: Narcissus tazetta var. chinensis, R2R3-MYB, repressor gene of anthocyain biosynthesis, expression of structural genes