CmMYB#7, an R3 MYB transcription factor, acts as a negative regulator of anthocyanin biosynthesis in chrysanthemum.
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ABSTRACT:
SUBMITTER: Xiang L
PROVIDER: S-EPMC6598077 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The generation of chrysanthemum (Chrysanthemum × morifolium) flower color is mainly attributed to the accumulation of anthocyanins. In the anthocyanin biosynthetic pathway in chrysanthemum, although all of the structural genes have been cloned, the regulatory function of R2R3-MYB transcription factor (TF) genes, which play a crucial role in determining anthocyanin accumulation in many ornamental crops, still remains unclear. In our previous study, four light-induced R2R3-MYB TF genes in chrysanthemum were identified using transcriptomic sequencing. In the present study, we further investigated the regulatory functions of these genes via phylogenetic and alignment analyses of amino acid sequences, which were subsequently verified by phenotypic, pigmental, and structural gene expression analyses in transgenic tobacco lines. As revealed by phylogenetic and alignment analyses, CmMYB4 and CmMYB5 were phenylpropanoid and flavonoid repressor R2R3-MYB genes, respectively, while CmMYB6 was an activator of anthocyanin biosynthesis, and CmMYB7 was involved in regulating flavonol biosynthesis. Compared with wild-type plants, the relative anthocyanin contents in the 35S:CmMYB4 and 35S:CmMYB5 tobacco lines significantly decreased (p < 0.05), while for 35S:CmMYB6 and 35S:CmMYB7, the opposite result was obtained. Both in the 35S:CmMYB4 and 35S:CmMYB5 lines, the relative expression of several anthocyanin biosynthetic genes in tobacco was significantly downregulated (p < 0.05); on the contrary, several genes were upregulated in the 35S:CmMYB6 and 35S:CmMYB7 lines. These results indicate that CmMYB4 and CmMYB5 negatively regulate anthocyanin biosynthesis in chrysanthemum, while CmMYB6 and CmMYB7 play a positive role, which will aid in understanding the complex mechanism regulating floral pigmentation in chrysanthemum and the functional divergence of the R2R3-MYB gene family in higher plants.
| S-EPMC6826627 | biostudies-literature
Project description:Chinese cabbage (Brassica rapa L.) leaves are purple in color due to anthocyanin accumulation and have nutritional and aesthetic value, as well as antioxidant properties. Here, we identified the R3 MYB transcription factor BrMYBL2.1 as a key negative regulator of anthocyanin biosynthesis. A Chinese cabbage cultivar with green leaves harbored a functional BrMYBL2.1 protein, designated BrMYBL2.1-G, with transcriptional repressor activity of anthocyanin biosynthetic genes. By contrast, BrMYBL2.1 from a Chinese cabbage cultivar with purple leaves carried a poly(A) insertion in the third exon of the gene, resulting in the insertion of multiple lysine residues in the predicted protein, designated BrMYBL2.1-P. Although both BrMYBL2.1 variants localized to the nucleus, only BrMYBL2.1-G interacted with its cognate partner BrTT8. Transient infiltration assays in tobacco leaves revealed that BrMYBL2.1-G, but not BrMYBL2.1-P, actively represses pigment accumulation by inhibiting the transcription of anthocyanin biosynthetic genes. Transient promoter activation assay in Arabidopsis protoplasts verified that BrMYBL2.1-G, but not BrMYBL2.1-P, can repress transcriptional activation of BrCHS and BrDFR, which was activated by co-expression with BrPAP1 and BrTT8. We determined that BrMYBL2.1-P may be more prone to degradation than BrMYBL2.1-G via ubiquitination. Taken together, these results demonstrate that BrMYBL2.1-G blocks the activity of the MBW complex and thus represses anthocyanin biosynthesis, whereas the variant BrMYBL2.1-P from purple Chinese cabbage cannot, thus leading to higher anthocyanin accumulation.
| S-EPMC8949199 | biostudies-literature
Project description:The MYB-bHLH-WDR (MBW) complex activates anthocyanin biosynthesis through the transcriptional regulation. RsMYB1 has been identified as a key player in anthocyanin biosynthesis in red radish (Raphanus sativus L.), but its partner bHLH transcription factor (TF) remains to be determined. In this study, we isolated a bHLH TF gene from red radish. Phylogenetic analysis indicated that this gene belongs to the TT8 clade of the IIIF subgroup of bHLH TFs, and we thus designated this gene RsTT8. Subcellular localization analysis showed that RsTT8-sGFP was localized to the nuclei of Arabidopsis thaliana protoplasts harboring the RsTT8-sGFP construct. We evaluated anthocyanin biosynthesis and RsTT8 expression levels in three radish varieties (N, C, and D) that display different red phenotypes in the leaves, root flesh, and root skins. The root flesh of the C variety and the leaves and skins of the D variety exhibit intense red pigmentation; in these tissues, RsTT8 expression showed totally positive association with the expression of RsMYB1 TF and of five of eight tested anthocyanin biosynthesis genes (i.e., RsCHS, RsCHI, RsF3H, RsDFR, and RsANS). Heterologous co-expression of both RsTT8 and RsMYB1 in tobacco leaves dramatically increased the expression of endogenous anthocyanin biosynthesis genes and anthocyanin accumulation. Furthermore, a yeast two-hybrid assay showed that RsTT8 interacts with RsMYB1 at the MYB-interacting region (MIR), and a transient transactivation assay indicated that RsTT8 activates the RsCHS and RsDFR promoters when co-expressed with RsMYB1. Complementation of the Arabidopsis tt8-1 mutant, which lacks red pigmentation in the leaves and seeds, with RsTT8 restored red pigmentation, and resulted in high anthocyanin and proanthocyanidin contents in the leaves and seeds, respectively. Together, these results show that RsTT8 functions as a regulatory partner with RsMYB1 during anthocyanin biosynthesis.
| S-EPMC5682339 | biostudies-literature
Project description:Pyrethrins are a mixture of terpenes, with insecticidal properties, that accumulate in the aboveground parts of the pyrethrum (Tanacetum cinerariifolium). Numerous studies have been published on the positive role of MYB transcription factors (TFs) in terpenoid biosynthesis; however, the role of MYB TFs in pyrethrin biosynthesis remains unknown. Here, we report the isolation and characterization of a T. cinerariifolium MYB gene encoding a R3-MYB protein, TcMYB8, containing a large number of hormone-responsive elements in its promoter. The expression of the TcMYB8 gene showed a downward trend during the development stage of flowers and leaves, and was induced by methyl jasmonate (MeJA), salicylic acid (SA), and abscisic acid (ABA). Transient overexpression of TcMYB8 enhanced the expression of key enzyme-encoding genes, TcCHS and TcGLIP, and increased the content of pyrethrins. By contrast, transient silencing of TcMYB8 decreased pyrethrin contents and downregulated TcCHS and TcGLIP expression. Further analysis indicated that TcMYB8 directly binds to cis-elements in proTcCHS and proTcGLIP to activate their expression, thus regulating pyrethrin biosynthesis. Together, these results highlight the potential application of TcMYB8 for improving the T. cinerariifolium germplasm, and provide insight into the pyrethrin biosynthesis regulation network.
| S-EPMC9602545 | biostudies-literature
Project description:Rose (Rosa hybrida) is one of most famous ornamental plants in the world, and its commodity value largely depends on its flower color. However, the regulatory mechanism underlying rose flower color is still unclear. In this study, we found that a key R2R3-MYB transcription factor, RcMYB1, plays a central role in rose anthocyanin biosynthesis. Overexpression of RcMYB1 significantly promoted anthocyanin accumulation in both white rose petals and tobacco leaves. In 35S:RcMYB1 transgenic lines, a significant accumulation of anthocyanins occurred in leaves and petioles. We further identified two MBW complexes (RcMYB1-RcBHLH42-RcTTG1; RcMYB1-RcEGL1-RcTTG1) associated with anthocyanin accumulation. Yeast one-hybrid and luciferase assays showed that RcMYB1 could active its own gene promoter and those of other EBGs (early anthocyanin biosynthesis genes) and LBGs (late anthocyanin biosynthesis genes). In addition, both of the MBW complexes enhanced the transcriptional activity of RcMYB1 and LBGs. Interestingly, our results also indicate that RcMYB1 is involved in the metabolic regulation of carotenoids and volatile aroma. In summary, we found that RcMYB1 widely participates in the transcriptional regulation of ABGs (anthocyanin biosynthesis genes), indicative of its central role in the regulation of anthocyanin accumulation in rose. Our results provide a theoretical basis for the further improvement of the flower color trait in rose by breeding or genetic modification.
| S-EPMC10261888 | biostudies-literature
Project description:Paeonia qiui is a wild tree peony native to China. Its leaves show a clear purple-red color from the germination to the flowering stage, and it has high leaf-viewing value. A MYB transcription factor gene, designated as PqMYB4, was isolated from leaves of P. qiui based on transcriptome datas. The full-length cDNA of PqMYB4 was 693 bp, encoding 230 amino acids. Sequence alignment and phylogenetic analysis revealed that PqMYB4 was a R2R3-MYB transcription factor clustered with AtMYB4 in Arabidopsis thaliana. Moreover, it contained a C1 motif, an EAR repression motif and a TLLLFR motif in the C-terminal domains, which were unique in transcription repression MYB. Subcellular location analysis showed that PqMYB4 was located in the cell nucleus. PqMYB4 was highly expressed in the late stage of leaf development, and was negatively correlated with the anthocyanin content. The petiole of wild-type Arabidopsis seedlings was deeper in color than the transgenic lines of PqMYB4 and showed a little purple-red color. The seed coat color of Arabidopsis seeds that overexpressed PqMYB4 gene was significantly lighter than that of wild-type seeds. In transgenic Arabidopsis, the expression level of AtCHS, AtCHI, AtDFR and AtANS were down-regulated significantly. These results showed that PqMYB4 was involved in the negative regulation of anthocyanin biosynthesis in tree peony leaves, which can control the anthocyanin pathway genes. Together, these findings provide a valuable resource with which to further study the regulatory mechanism of anthocyanin biosynthesis in the leaf of P. qiui. They also benefit the molecular breeding of tree peony cultivars with colored leaf.
| S-EPMC7461502 | biostudies-literature
Project description:Chrysanthemums (Chrysanthemum morifolium Ramat.) exhibit a variety of flower colors due to their differing abilities to accumulate anthocyanins. One MYB member, CmMYB6, has been verified as a transcription regulator of chrysanthemum genes involved in anthocyanin biosynthesis; however, the co-regulators for CmMYB6 remain unclear in chrysanthemum. Here, the expression pattern of CmbHLH2, which is clustered in the IIIf bHLH subgroup, was shown to be positively correlated with the anthocyanin content of cultivars with red, pink and yellow flower colors, respectively. CmbHLH2 significantly upregulated the CmDFR promoter and triggered anthocyanin accumulation when co-expressed with CmMYB6. Yeast one-hybrid analyses indicated that CmbHLH2 was able to bind directly to the CmDFR promoter. Moreover, yeast two-hybrid assays indicated protein-protein interaction between CmbHLH2 and CmMYB6. These results suggest that CmbHLH2 is the essential partner for CmMYB6 in regulating anthocyanin biosynthesis in chrysanthemum.
| S-EPMC4664390 | biostudies-literature
Project description:BackgroundChinese cherry [Cerasus pseudocerasus (Lindl.) G.Don] (syn. Prunus pseudocerasus Lindl.) is an economically important fruiting cherry species with a diverse range of attractive colors, spanning from the lightest yellow to the darkest black purple. However, the MYB transcription factors involved in anthocyanin biosynthesis underlying fruit color variation in Chinese cherry remain unknown.ResultsIn this study, we characterized the R2R3-MYB gene family of Chinese cherry by genome-wide identification and compared it with those of 10 Rosaceae relatives and Arabidopsis thaliana. A total of 1490 R2R3-MYBs were classified into 43 subfamilies, which included 29 subfamilies containing both Rosaceae MYBs and AtMYBs. One subfamily (S45) contained only Rosaceae MYBs, while three subfamilies (S12, S75, and S77) contained only AtMYBs. The variation in gene numbers within identical subfamilies among different species and the absence of certain subfamilies in some species indicated the species-specific expansion within MYB gene family in Chinese cherry and its relatives. Segmental and tandem duplication events primarily contributed to the expansion of Chinese cherry R2R3-CpMYBs. The duplicated gene pairs underwent purifying selection during evolution after duplication events. Phylogenetic relationships and transcript profiling revealed that CpMYB10 and CpMYB4 are involved in the regulation of anthocyanin biosynthesis in Chinese cherry fruits. Expression patterns, transient overexpression and VIGS results confirmed that CpMYB10 promotes anthocyanin accumulation in the fruit skin, while CpMYB4 acts as a repressor, inhibiting anthocyanin biosynthesis of Chinese cherry.ConclusionsThis study provides a comprehensive and systematic analysis of R2R3-MYB gene family in Chinese cherry and Rosaceae relatives, and identifies two regulators, CpMYB10 and CpMYB4, involved in anthocyanin biosynthesis in Chinese cherry. These results help to develop and utilize the potential functions of anthocyanins in Chinese cherry.
| S-EPMC11323479 | biostudies-literature
Project description:BackgroundR2R3-MYB transcription factors (TFs) play important roles in plant growth and development, and response to biotic and abiotic stresses. However, their regulatory mechanisms in wound-induced anthocyanin biosynthesis in woody plants are largely unknown.ResultsIn this work, we report that expression of anthocyanin biosynthesis genes (ABGs) were activated by PdMYB118, a MYB TF encoding gene from Populus deltoids, and the activation of PdMYB118 was significantly enhanced by PdTT8, a bHLH protein, through its direct interaction with PdMYB118. PdMYB118 and some ABGs were evidently induced by wound induction and methyl jasmonate (MeJA) treatment. Overexpression of PdMYB118 promoted anthocyanin accumulation in transgenic poplar upon wound induction. Furthermore, a poplar JASMONATE ZIM-domain (JAZ) protein, PtrJAZ1, repressed the transcriptional function of PdMYB118/PdTT8 complex by binding to PdTT8, and wound stimulated the biosynthesis of jasmonic acid (JA) and the degradation of PtrJAZ1.ConclusionsBased on these observations, we proposed that PtrJAZ1 degradation triggered the expression of ABGs, leading to increased biosynthesis of anthocyanins in the wounded leaves of transgenic poplar. Therefore, our findings not only illustrate the crucial role of PdMYB118 in wound-induced anthocyanin biosynthesis in poplar, but also provide a molecular basis for the genetic engineering of colorful tree species.
| S-EPMC7168848 | biostudies-literature
Project description:Artemisinin is a secondary metabolite extracted from Artemisia annua. As an effective antimalarial component certified by WHO, artemisinin has extensive economical values. Numerous studies about transcription factors positively regulating artemisinin biosynthesis have been published while negative regulators are rarely reported. In the present study, we identified AaMYB15 as the first R2R3-MYB that negatively regulates artemisinin biosynthesis in A. annua. Experimental evidences showed that AaMYB15 is a transcription factor within nucleus and predominantly expressed in glandular secretory trichomes (GSTs) in A. annua where artemisinin is synthesized and accumulated. The expression of AaMYB15 was induced by dark and JA treatment. Overexpression of AaMYB15 led to a significant decline in the expression levels of key enzyme genes ADS, CYP, DBR2, and ALDH1 and a significant decrease in the artemisinin contents of transgenic A. annua. AaMYB15 directly bound to the promoter of AaORA, a reported positive regulator of artemisinin biosynthesis in JA signaling pathway, to repress its transcriptional activity, thus downregulating the expression levels of downstream key enzyme genes and negatively regulating the artemisinin biosynthesis. Our study provides candidate gene for improvement of A. annua germplasm and new insights into the artemisinin biosynthesis regulation network mediated by light and JA.
| S-EPMC8174473 | biostudies-literature