<i>NtMYB3</i>, an R2R3-MYB from Narcissus, Regulates Flavonoid Biosynthesis

• Main Authors: Muhammad Anwar, Weijun Yu, Hong Yao, Ping Zhou, Andrew C. Allan, Lihui Zeng
• Format: Article
• Language: English
• Published: MDPI AG 2019-11-01
• Series: International Journal of Molecular Sciences
• Subjects: chinese narcissus; flavonol; r2r3-myb; flavonoid repressor; anthocyanin
• Online Access: https://www.mdpi.com/1422-0067/20/21/5456

R2R3-MYB transcription factors play important roles in the regulation of plant flavonoid metabolites. In the current study, <i>NtMYB3</i>, a novel R2R3-MYB transcriptional factor isolated from Chinese narcissus (<i>Narcissus tazetta</i> L. var. <i>chinensis</i>), was functionally characterized. Phylogenetic analysis indicated that NtMYB3 belongs to the AtMYB4-like clade, which includes repressor MYBs involved in the regulation of flavonoid biosynthesis. Transient assays showed that <i>NtMYB3</i> significantly reduced red pigmentation induced by the potato anthocyanin activator <i>StMYB-AN1</i> in agro-infiltrated leaves of tobacco. Over-expression of <i>NtMYB3</i> decreased the red color of transgenic tobacco flowers, with qRT-PCR analysis showing that <i>NtMYB3</i> repressed the expression levels of genes involved in anthocyanin and flavonol biosynthesis. However, the proanthocyanin content in flowers of transgenic tobacco increased as compared to wild type. <i>NtMYB3</i> showed expression in all examined narcissus tissues; the expression level in basal plates of the bulb was highest. A 968 bp promoter fragment of narcissus <i>FLS</i> (<i>NtFLS</i>) was cloned, and transient expression and dual luciferase assays showed <i>NtMYB3</i> repressed the promoter activity. These results reveal that <i>NtMYB3</i> is involved in the regulation of flavonoid biosynthesis in narcissus by repressing the biosynthesis of flavonols, and this leads to proanthocyanin accumulation in the basal plate of narcissus.