Functional analysis of NtMYB15 from Narcissus tazetta var. chinensis in transgenic aromatic plants (Petunia hybrida and Nicotiana tabacum) regulating the colour and aroma of the flowers

R2R3-MYB transcription factors, integral members of the MYB transcription factors (TFs) family, participate in regulating plant secondary metabolite synthesis, developmental processes, and biotic/abiotic stress responses. However, their roles in the biosynthesis of floral volatile organic compounds (VOCs) remain largely unexplored. In this study, we identified an R2R3-MYB TF from the petals of Narcissus tazetta var. chinensis , and named it NtMYB15. It's harboring the conserved R2R3 domain. NtMYB15 belongs to the S3 subgroup of the R2R3-MYB family. Through yeast transcriptional activation activity assays and subcellular localization experiments, we confirmed that NtMYB15 is a nuclear-localized TF with transcriptional activation potential. Additionally, yeast two-hybrid and bimolecular fluorescence complementation assays demonstrated that NtMYB15 can interact with BHLH2 and WD40 proteins, forming the MYB-bHLH-WD40 (MBW) complex. In transgenic Petunia hybrida , overexpression of NtMYB15 led to a significant reduction in the methyl benzoate content of volatile benzenoid/phenylpropanoid compounds (FVBP). Real-time fluorescence quantitative PCR (qPCR) analysis showed that the transcript levels of genes involved in the methyl benzoate biosynthetic pathway were notably downregulated in transgenic P. hybrida . In transgenic tobacco, overexpression of NtMYB15 resulted in lighter flower color, increased flux of FVBP, and enhanced production of volatile terpenes, suggesting that NtMYB15 can regulate both flower aroma and color. qPCR analysis of genes (e.g., DXR , TPS ) showed differential expression patterns between transgenic and non-transgenic tobacco, further validating these findings. Collectively, our results indicate that NtMYB15 is a nuclear-localized transcriptional activator that co-regulates floral VOC biosynthesis and flower color, providing novel insights into the regulatory mechanisms underlying these processes in plants. • The first transcription factor co-regulating color and fragrance in Narcissus. • Dual-phenotype validation of flower color and fragrance. • Protein interaction forms the MBW complex (MYB-bHLH-WD40 complex).