The R2R3-MYB Transcriptional Repressor TgMYB4 Negatively Regulates Anthocyanin Biosynthesis in Tulips (Tulipa gesneriana L.)

Abstract

Anthocyanins play a paramount role in color variation and significantly contribute to the economic value of ornamental plants. The conserved activation complex MYB-bHLH-WD40 (MBW; MYB: v-myb avian myeloblastosis viral oncogene homolog; bHLH: basic helix–loop–helix protein; WD40:WD-repeat protein) involved in anthocyanin biosynthesis has been thoroughly researched, but there have been limited investigations into the function of repressor factors. In this study, we characterized TgMYB4, an R2R3-MYB transcriptional repressor which is highly expressed during petal coloration in red petal cultivars. TgMYB4-overexpressing tobaccos exhibited white or light pink petals with less anthocyanin accumulation compared to control plants. TgMYB4 was found to inhibit the transcription of ANTHOCYANIDIN SYNTHASE (TfANS1) and DIHYDRO-FLAVONOL-4-REDUCTASE (AtDFR), although it did not bind to their promoters. Moreover, the TgMYB4 protein was able to compete with the MYB activator to bind to the :bHLHprotein, thereby suppressing the function of the activator MBW complex. These findings demonstrate that TgMYB4 plays a suppressive role in the regulation of anthocyanin synthesis during flower pigmentation.

Integrated Transcriptome and Metabolome Analyses Reveal Bamboo Culm Color Formation Mechanisms Involved in Anthocyanin Biosynthetic in Phyllostachys nigra

“…These transcription factors are capable of forming the MBW complex, which has been shown to play a critical role in anthocyanin synthesis in a wide range of plant species [44,45]. The regulation of anthocyanins by MYB has been studied in Arabidopsis [46], Rosa rugose [47], Tulipa gesneriana [48], etc. According to the phylogenetic tree, PnMYB1 is grouped in the same subgroup as AtMYB3 and exhibits a comparable role in restricting anthocyanin synthesis by repressing phenylalanine metabolism [28].…”

Genome-Wide Identification and Expression Analysis of the MYB Transcription Factor Family in Salvia nemorosa

“…As a result, our future investigations will involve analyzing the selected genes, including SnMYB90, SnMYB6, and SnMYB75, through stable overexpression, gene-editing, and silencing experiments. Additionally, transient expression system, yeast one-hybrid, and EMSA experiments will be utilized to evaluate the transcriptional regulatory function of the MYB transcription factor for downstream anthocyanin biosynthetic enzyme genes [57,58].…”