Cloning and Functional Analysis of NtMYB9 in ‘Jinzhanyintai’ of Narcissus tazetta var. chinensis

Abstract

Narcissus tazetta var. chinensis M.Roem. (Chinese Narcissus) is a traditional and famous flower in China, and its corona shows a transition from green to yellow with the opening of flowers, which is of great ornamental value. To investigate the molecular mechanism of the corona color-forming in the Chinese Narcissus, in this study, a MYB gene was screened from the transcriptome of the corona by bioinformatics analysis methods, named NtMYB9. The expression level of the NtMYB9 gene was significantly higher in the corona than in the tepal, filament, ovary and leaf, and reached the highest level at the fourth period of complete coloration of the corona. The full-length sequence of the NtMYB9 coding region was cloned using the corona cDNA as a template. Sequence analysis revealed that NtMYB9 protein contained R2 and R3 domains, phylogenetic tree analysis showed that the NtMYB9 protein was most closely related to flavonol activators. Subcellular localization showed that NtMYB9 was localized in the nucleus. The overexpression of NtMYB9 gene into tobacco leaves and the expression level of seven enzyme genes related to the flavonoid biosynthesis pathway were significantly up-regulated. The transient transformation of Petunia × hybrida (Petunia) and Phalaenopsis aphrodite (Phalaenopsis) significantly revealed that the NtMYB9 gene could turn flowers yellow. These results suggest that the NtMYB9 gene is involved in the positive regulation of flavonoid biosynthesis in the Chinese Narcissus and may promote the synthesis of flavonols. In conclusion, these findings provide a valuable resource for further studies on the regulatory mechanism of the flavonoid biosynthesis pathway, and they are also beneficial to the molecular breeding of Chinese Narcissus.