Regulation Of Anthocyanin Biosynthesis Research Articles

5-Aminolevulinic acid activates the MdWRKY71-MdMADS1 module to enhance anthocyanin biosynthesis in apple

5-Aminolevulinic acid (ALA), as a natural plant growth regulator, is well known for promoting red fruit coloring by enhancing anthocyanin accumulation. However, the underlying mechanisms remain elusive. In this study, we firstly demonstrated that ALA upregulates gene expression of the transcription factor MdMADS1, which in turn directly binds to and activates transcription of the key anthocyanin biosynthetic genes, MdCHS and MdUFGT. Then, we identified a novel WRKY transcription factor, MdWRKY71, that interacts with MdMADS1. Through gene manipulation, we revealed that MdWRKY71 plays a pivotal role in ALA-induced anthocyanin accumulation, highlighting its regulatory significance in this process. Further investigation unveiled that MdWRKY71 not only activates MdMADS1 transcription but also enhances its transcriptional activation on its target genes, MdCHS and MdUFGT. Additionally, we discovered that MdWRKY71 independently binds to and activates the transcription of two other anthocyanin biosynthetic genes, MdANS and MdDFR. The protein–protein interaction between MdWRKY71 and MdMADS1 amplifies the transcriptional activation of these genes by MdWRKY71. These findings delineate a fine and complex regulatory framework where MdWRKY71 and MdMADS1 coordinately regulate anthocyanin biosynthesis in apples, providing new insights into the molecular control of fruit coloration and offering potential target genes for breeding aimed at enhancing fruit quality.

DcWRKY15 positively regulates anthocyanin biosynthesis during petal coloration in Dianthus caryophyllus

Petal pigmentation in carnations is closely associated with the biosynthesis of anthocyanins. This biosynthetic process is tightly regulated by transcription factors, which activate or repress key genes involved in anthocyanin production. Here, we aim to explore the mechanisms involved in the transcriptional regulation of anthocyanin biosynthesis in carnation petals. We identified DcWRKY15 as a critical regulator influencing anthocyanin production in these petals. DcWRKY15 expression showed a strong correlation with the expression levels of genes associated with anthocyanin biosynthesis, peaking during early petal development stages. The findings from the dual-LUC, VIGS, Y1H and EMSA assays demonstrated that DcWRKY15 played a positive regulatory role in anthocyanin biosynthesis. DcWRKY15 achieved this by binding directly to the promoters of DcCHS and DcF3H, thereby enhancing their expression. Additionally, DcWRKY15 interacts with the repressor DcMYB2, which reduces its capacity to enhance anthocyanin biosynthesis, particularly during the later stages of petal development. These findings offer new insights into the molecular mechanisms responsible for petal coloration in carnations, highlighting the complex interplay between activator and repressor transcription factors.

Genome-wide identification of the bHLH gene family and the mechanism regulation of anthocyanin biosynthesis by ChEGL1 in Cerasus humilis.

Cerasus humilis is a fruit tree with enormous potential economic value, and its fruit is rich in various bioactive substances. The basic helix loop helix (bHLH) gene family plays an important role in the biosynthesis of plant anthocyanins. However, there was no research on the ChbHLH gene family in C. humilis. In this study, 114 ChbHLH genes were identified from the C. humilis genome and divided into 17 subgroups. Then, evolutionary relationships, conserved motifs, gene structures, and cis-acting elements were analyzed. By predicting the interaction network between ChbHLH proteins and ChMYB1, it was found that ChbHLH44 (here named as ChEGL1) was located at the core of the interaction network. Further experiments revealed that ChEGL1 and ChMYB1 could interact with each other both in vivo and in vitro. In addition, ChEGL1 significantly increased the anthocyanin content in transgenic tomato plants. This study provides a comprehensive understanding of the ChbHLH gene family and supports further enrichment of the regulation mechanism of anthocyanin biosynthesis in C. humilis fruit.

Two tandem R2R3 MYB transcription factor genes cooperatively regulate anthocyanin accumulation in potato tuber flesh.

Anthocyanin biosynthesis and accumulation determines the colour of tuber flesh in potato (Solanum tuberosum) and influences nutritional quality. However, the regulatory mechanism behind anthocyanin biosynthesis in potato tuber flesh remains unclear. In this study, we identified the Pigmented tuber flesh (Pf) locus through a genome-wide association study using 135 diploid potato landraces. Genome editing of two tandem R2R3 MYB transcription factor genes, StMYB200 and StMYB210, within the Pf locus demonstrated that both genes are involved in anthocyanin biosynthesis in tuber flesh. Molecular and biochemical assays revealed that StMYB200 promotes StMYB210 transcription by directly binding to a 1.7-kb insertion present in the StMYB210 promoter, while StMYB210 also regulates its own expression. Furthermore, StMYB200 and StMYB210 both activated the expression of the basic helix-loop-helix transcription factor gene StbHLH1 and interacted with StbHLH1 to regulate anthocyanin biosynthesis. An analysis of the StMYB210 promoter in different diploid potato accessions showed that the 1.7-kb insertion is associated with flesh colour in potato. These findings reveal the genetic and molecular mechanism by which the Pf locus regulates anthocyanin accumulation in tuber flesh and provide an important reference for breeding new potato varieties with colourful flesh.

AaMYB61-like and AabHLH137 jointly regulate anthocyanin biosynthesis in Actinidia arguta

BackgroundRed Actinidia arguta has recently become highly popular because of its red appearance resulting from anthocyanin accumulation, and has gradually become an important breeding direction. However, regulators involved in anthocyanin biosynthesis have not been fully characterized in A. arguta.ResultsHere, we demonstrated that a key R2R3-MYB transcription factor, AaMYB61-like, plays a crucial role in A. arguta anthocyanin biosynthesis. The RT-qPCR results revealed that transient overexpression of AaMYB61-like in A. arguta fruit at 90–100 DAFB significantly promoted anthocyanin biosynthesis, as did the gene expression levels of AaCHS, AaCHI, AaF3H, AaLDOX, and AaF3GT, whereas the result of VIGS revealed the opposite results in A. arguta fruit at 105–115 DAFB. A transcriptional activation assay indicated that AaMYB61-like exhibited transcriptional activation activity. Y1H and LUC assays revealed that AaMYB61-like activates the promoters of AaCHS, AaLDOX, and AaF3GT. In addition, AabHLH137 was found to be related to fruit color from the transcriptome data. We demonstrated that AaMYB61-like promotes anthocyanin biosynthesis by interacting with AabHLH137 via Y2H, BiFC, and Agrobacterium-mediated co-transformation.ConclusionsOur study not only reveals the functions of AaMYB61-like and AabHLH137 in anthocyanin regulation, but also broadly enriches color regulation theory, establishing a foundation for clarifying the molecular mechanism of fruit coloration in kiwifruit.

CmBBX28-CmMYB9a Module Regulates Petal Anthocyanin Accumulation in Response to Light in Chrysanthemum.

Light is one of the most important environmental factors that affect plant growth and development. It also stimulates anthocyanin biosynthesis in plants. However, the precise molecular mechanisms through which light regulates anthocyanin biosynthesis, particularly in non-model plant species, remain poorly understood. In this study, we discovered a CmBBX28-CmMYB9a molecular module that is responsive to light and regulates anthocyanin biosynthesis in chrysanthemums. Specifically, CmBBX28 interacts with CmMYB9a, interfering with its binding to the promoters of target genes and reducing the protein abundance of CmMYB9a. This interaction downregulates the transcription of CmMYB9a's downstream anthocyanin-associated genes, CmCHS, CmDFR, and CmUFGT. The expression of CmBBX28 was induced in the dark, and the accumulated CmBBX28 proteins interfered with the activation of CmMYB9a during anthocyanin biosynthesis. Concurrently, darkness also inhibited the expression of CmMYB9a to some extent. In contrast, light significantly induced the expression of CmMYB9a and suppressed the expression of CmBBX28, resulting in increased anthocyanin accumulation in chrysanthemum petals. Our findings reveal the mechanism by which light regulates anthocyanin biosynthesis in chrysanthemum flower petals.

Integrated metabolomic and transcriptomic analysis of anthocyanin metabolism in wheat pericarp

BackgroundWheat seeds display different colors due to the types and contents of anthocyanins, which is closely related to anthocyanin metabolism. In this study, a transcriptomic and metabolomic analysis between white and purple color wheat pericarp aimed to explore some key genes and metabolites involved in anthocyanin metabolism.ResultsTwo wheat cultivars, a white seed cultivar Shiluan02-1 and purple seed cultivar Hengzi151 were used to identify the variations in differentially expressed genes (DEGs) and differentially accumulated flavonoids (DAFs). Based on metabolomic data, 314 metabolites and 191 DAFs were identified. Chalcone, flavonol, pro-anthocyanidin and anthocyanidin were the most differentially accumulated flavonoid compounds in Hengzi151. 2610 up-regulated and 2668 down-regulated DEGs were identified according to transcriptomic data. The results showed that some structural genes in anthocyanin synthesis pathway were prominently activated in Hengzi151, such as PAL, CAD, CHS and so on. Transcription factors (TFs) of MYB, bHLH, WD40 and some other TFs probably involved in regulating anthocyanin biosynthesis were identified. Some genes from hormone synthetic and signaling pathways that may participate in regulating anthocyanin biosynthesis also have been identified.ConclusionsOur results provide valuable information on the candidate genes and metabolites involved in the anthocyanin metabolism in wheat pericarp.

Post-transcriptional and post-translational regulation of anthocyanin biosynthesis in sweetpotato by Ib-miR2111 and IbKFB: Implications for health promotion.

Sweetpotato (Ipomoea batatas (L.) Lam.) is a genetically intricate hexaploid crop. The purple-fleshed variety, enriched with anthocyanin pigments, is an outstanding source for creating high-value functional products. Previous research on anthocyanin biosynthesis has primarily focused on the above-ground plant parts at the transcriptional level. However, the regulatory mechanisms underlying anthocyanin accumulation in underground tuberous roots of sweetpotato remain largely unexplored. This study aimed to elucidate the post-transcriptional and post-translational mechanisms of Ib-miR2111 and its target gene IbKFB in anthocyanin synthesis in sweetpotato. Genetic manipulation techniques were used to validate the function of Ib-miR2111 and IbKFB in anthocyanin biosynthesis in sweetpotato. To investigate how IbKFB works, a series of protein interaction assays, including yeast two-hybrid (Y2H), bimolecular fluorescence complementation (BiFC), GST pull-down, co-immunoprecipitation (Co-IP), and ubiquitination, were conducted. Additionally, the impact of anthocyanin extracts from the genetically modified sweetpotato lines on inflammatory cells morphology, cytokine expression, and cell proliferation were evaluated using in vitro assays. Purple-fleshed sweetpotato (PFSP) varieties exhibited elevated Ib-miR2111 expression compared to white-fleshed sweetpotato (WFSP) varieties, with an inverse expression pattern in IbKFB. Genetic manipulations, including overexpression, CRISPR/Cas9 knockouts, and targeted mutations, confirmed their critical roles in anthocyanin modulation. Furthermore, IbKFB's interactions and ubiquitination with phenylalanine ammonia-lyase 1 (IbPAL1) and glyceraldehyde-3-phosphate dehydrogenase 1 (IbGAPCp1) were elucidated, revealing intricate regulatory mechanisms. Enhanced anthocyanin content showed significant effects on inflammatory cell morphology, cytokine expression, and cell proliferation. This study provides new insights into the regulatory mechanisms of Ib-miR2111 and IbKFB in anthocyanin biosynthesis and suggests potential health benefits of anthocyanin-rich sweetpotatoes.

CaHY5 Mediates UV-B Induced Anthocyanin Biosynthesis in Purple Pepper

Anthocyanins are important flavonoid compounds in plants that are associated with the color formation and antioxidant activity of flowers, fruits, and other organs. Ultraviolet B radiation (UV-B) is one of the key environmental factors that influence anthocyanin accumulation in plants and HY5 is involved in plant photomorphogenesis. However, the molecular mechanism of the signal network of UV-B regulating anthocyanin biosynthesis in capsicum via HY5 remains unclear. In this study, we identified the transcription factor CaHY5, which mediates UV-B signaling, and demonstrated its regulatory role in anthocyanin biosynthesis in purple pepper (Capsicum annuum L.). The results showed that there were photoresponsive and hormone-responsive elements on the CaHY5 promoter that responded to UV-B, indoleacetic acid, salicylic acid, 6-benzyladenine, abscisic acid, and melatonin treatments. UV-B treatment induced the expression of CaHY5 and anthocyanin structural genes. CaHY5 gene-silenced positive plants showed different degrees of the yellowing phenomenon, which affected the expression of the anthocyanin biosynthesis structural gene. The expression levels of anthocyanin biosynthesis-related genes in CaHY5-silenced positive plants increased considerably. This study provides insights into the role of CaHY5 in UV-B-induced anthocyanin biosynthesis in purple pepper.

Transcriptomic Insights into Higher Anthocyanin Accumulation in 'Summer Black' Table Grapes in Winter Crop Under Double-Cropping Viticulture System.

Anthocyanins are responsible for grape (Vitis vinifera L.) skin color. To obtain a more detailed understanding of the anthocyanin regulatory networks across' the summer and winter seasons in grapes under a double-cropping viticulture system, the transcriptomes of 'Summer Black' grapes were analyzed using RNA sequencing. The average daily temperature during the harvest stage in the summer crop, ranging from 26.18 °C to 32.98 °C, was higher than that in the winter crop, ranging from 11.03 °C to 23.90 °C. Grapes from the winter crop accumulated a greater content of anthocyanins than those from the summer crop, peaking in the harvest stage (E-L38) with 207.51 mg·100 g-1. Among them, malvidin-3-O-glucoside (Mv-3-G) had the highest monomer content, accounting for 32%. The content of Cy-3-G during winter increased by 55% compared to summer. KEGG analysis indicated that the flavonoid biosynthesis and circadian rhythm-plant pathways are involved in the regulation of anthocyanin biosynthesis during fruit development. Pearson's coefficient showed significant positive correlations between anthocyanin content and the VvDFR, VvUFGT, VvOMT, VvMYB, and VvbHLH genes in the winter crop; at full veraison stage, their expressions were 1.34, 1.98, 1.28, 1.17, and 1.34 times greater than in summer, respectively. The higher expression of VvUFGT and VvOMT led to higher contents of Cy-3-G and Mv-3-G in the winter berries, respectively.

Impact of Hormone on Growth and GA3 Regulation of Anthocyanin Biosynthesis in Suspension-Culture Cells of Cyclocarya paliurus.

Hormones are effective in regulating plant metabolism and, therefore, are often used in plant cell culture to increase the yield of target products. This study investigated the effects of hormones on the growth and anthocyanin biosynthesis of suspension-cultured red Cyclocarya paliurus cells. Additionally, the mechanism by which gibberellin induces anthocyanin biosynthesis was explored through multi-omics integrated analysis and the assay of the dynamic changes in signaling molecule concentration. The results showed that the total anthocyanin content and yield of suspension-cultured cells, when induced by 1.0 mg L⁻¹ Gibberellin A3 (GA3), experienced increases of 1.92- and 1.83-fold, respectively. The application of exogenous GA3 activated the synthesis and transduction of four signaling molecules, that is, nitric oxide (NO), hydrogen peroxide (H2O2), salicylic acid (SA), and jasmonic acid (JA), in the cells and altered the expression patterns of transcription factors. The altered expression of transcription factors upregulated the expression of anthocyanin biosynthetic genes such as anthocyanin-3-O-glucosyl transferase and leucoanthocyanidin dioxygenase, while downregulated the expression of anthocyanin reductase and flavonoid 3',5',-hydroxylase, which activated the anthocyanin biosynthesis pathway, ultimately leading to a significant increase in anthocyanin biosynthesis. This research work establishes a foundation for further research on the role of hormones in regulating anthocyanin biosynthesis in suspension-cultured plant cells.

Evolutionary analysis of anthocyanin biosynthetic genes: insights into abiotic stress adaptation.

Anthocyanin regulation can be fruitfully explored from a diverse perspective by studying distantly related model organisms. Land plants pioneers faced a huge evolutionary leap, involving substantial physiological and genetic changes. Anthocyanins have evolved alongside these changes, becoming versatile compounds capable of mitigating terrestrial challenges such as drought, salinity, extreme temperatures and high radiation. With the accessibility of whole-genome sequences from ancient plant lineages, deeper insights into the evolution of key metabolic pathways like phenylpropanoids have emerged. Despite understanding the function of anthocyanins under stress, gaps remain in uncovering the precise metabolic and regulatory mechanisms driving their overproduction under stressful conditions. For example, the regulatory effect of reactive oxygen species (ROS) on well-known transcription factors like MYBs is not fully elucidated. This manuscript presents an evolutionary analysis of the anthocyanin biosynthetic pathway to elucidate key genes. CINNAMATE 4-HYDROXYLASE (C4H) and CHALCONE ISOMERASE (CHI2) received particular attention. C4H exposes remarkable differences between aquatic and land plants, while CHI2 demonstrates substantial variation in gene copy number and sequence similarity across species. The role of transcription factors, such as MYB, and the involvement of ROS in the regulation of anthocyanin biosynthesis are discussed. Complementary gene expression analyses under abiotic stress in Arabidopsis thaliana, Selaginella moellendorffii, and Marchantia polymorpha reveal intriguing gene-stress relationships. This study highlights evolutionary trends and the regulatory complexity of anthocyanin production under abiotic stress, providing insights and opening avenues for future research.

A novel bHLH transcription factor LlbHLH12 negatively regulates anthocyanin biosynthesis during Lycoris longituba petal development

A novel bHLH transcription factor LlbHLH12 negatively regulates anthocyanin biosynthesis during Lycoris longituba petal development

Integrated Transcriptome and Metabolome Analysis Revealed Mechanism Underlying Anthocyanin Biosynthesis During Flower Color Formation in Lagerstroemia indica

Lagerstroemia indica is a widely used ornamental woody plant known for its summer flowering and significant ornamental and economic value. While L. indica boasts a variety of rich flower colors, the molecular mechanisms underlying this color formation remain unclear. In this study, we selected three different flower colors of L. indica—white (W), red (R), and purple (P)—for transcriptome and metabolome analysis. The metabolome analysis identified 538 flavonoids, with 22 anthocyanins highly accumulated in the red and purple flowers. RNA-seq analysis annotated a total of 35,505 genes. Furthermore, we identified 42 differentially expressed genes (DEGs) involved in anthocyanin biosynthesis, with their expression levels aligning with anthocyanin content. Correlation analysis revealed that 19 MYB and 11 bHLH transcription factors are likely involved in anthocyanin biosynthesis. Additionally, we identified 59 auxin biosynthesis and signaling-related genes that are positively correlated with anthocyanin-related genes and metabolites, suggesting that auxin may play a role in regulating anthocyanin biosynthesis in L. indica. This study provides valuable insights into the regulatory mechanisms underlying anthocyanin accumulation and color formation in L. indica petals and identifies several potential genes, laying the groundwork for further research on regulatory mechanisms and genetic improvement of L. indica.

Overexpression of MYB transcription factor LrAN2 from Lycium ruthenicum activated the anthocyanin biosynthesis in the leaf and fruit of Lycium barbarum

AN2 was thought to be the key gene inducing the fruit color differentiation of Lycium barbarum and Lycium ruthenicum, but there was no direct evidence. In this study, AN2 from L. ruhtenicum was overexpressed in L. barbarum to conform its function in regulating anthocyanin biosynthesis. The results showed that the stems, leaves, and fruits of transgenic plants were purple and contained significantly higher anthocyanin levels compared to the wild-type plants. Transcriptome analysis of leaf and fruit identified 5,832 differentially expressed genes (DEGs) in leaves and 2,029 DEGs in fruits, with 910 genes common to both tissues. GO and KEGG pathway enrichment analyses indicated a significant impact of LrAN2 on flavonoid biosynthesis and anthocyanin biosynthesis. The structural genes involved in the anthocyanin pathway, such as 4CL, CHS, F3H, F3’5’H, DFR, ANS, and UFGT, were up-regulated in transgenic lines, while the expression of transcription factors bHLH and WD40 were remained unchanged. These findings confirm the role of LrAN2 in the color differentiation of L. barbarum and L. ruthenicum and highlight its potential for the genetic enhancement of anthocyanin content in L. barbarum and other Solanaceae species.

Combined transcriptomic, metabolomic and physiological analysis reveals the key role of nitrogen, but not phosphate and potassium in regulating anthocyanin biosynthesis induced by nutrient deficiency in Eucalyptus

Anthocyanin biosynthesis in Eucalyptus plants can be flexibly and rapidly modulated in response to hormones or environmental stimuli, including nutrient deprivation (ND). However, the underlying mechanism of ND in inducing anthocyanin biosynthesis in plants remains largely elusive. In this study, we discovered that anthocyanin levels in leaves and stems could well reflect nitrogen availability in Eucalyptus. Supplementation with nitrogen, but not with phosphate or potassium, effectively inhibited ND-induced anthocyanin biosynthesis. To further investigate how nitrogen regulates this process, comprehensive time-resolved transcriptomic and targeted metabolomic analyses were conducted. The results revealed that 3405, 2706, and 3153 genes were differentially regulated by nitrogen treatment at 1, 2, and 3 d, respectively. Pathway analysis indicated the majority of the enriched KEGG pathways were associated with cellular metabolism, such as amino acid and flavonoid biosynthesis. Moreover, metabolomic analysis showed that the most abundantly accumulated anthocyanins, cyanidin-3-O-galactoside and cyanidin-3-O-glucoside, along with key intermediates in the flavonoid pathway, were downregulated by nitrogen treatment. Furthermore, nitrogen-responsive MYB-bHLH-WDR complex genes were identified, including six EgrMYB113 family members. Overexpression of one of the EgrMYB113-like genes induced anthocyanin biosynthesis in the transgenic hairy roots of Eucalyptus. Interestingly, mutation of AtMYB113 inhibited nitrogen deficiency-induced anthocyanin biosynthesis in Arabidopsis, suggesting that MYB113 is a novel N-responsive MYB transcriptional regulator of anthocyanin biosynthesis. Additionally, nitrogen treatment upregulated a few GA biosynthesis genes while simultaneously downregulated the expression of several GA2ox genes. Exogenous application of GA3 decreased ND-induced anthocyanin biosynthesis. Conclusively, this study provides novel insights into the molecular mechanism of nitrogen in the regulation of anthocyanin biosynthesis in Eucalyptus.

MYB-1 regulates anthocyanin biosynthesis in Magnolia wufengensis

Anthocyanin is an essential pigment in all major horticultural crops especially in ornamental trees. Magnolia wufengensis (new species of Magnolia) with red color flower was recently found as a popular species for ornamental use, but anthocyanin synthesis and regulation in M. wufengensis are poorly understood. Herein, transcriptome analysis was used to decipher the gene network associated with anthocyanin biosynthesis. An R2R3-like MwMYB-1 transcription factor was found. MwMYB-1 overexpression resulted in anthocyanin accumulation in tobacco and Arabidopsis. MwMYB-1 worked independently rather than forming a protein complex with bHLH or WD40 protein. According to MwMYB-1 DAP-seq analysis in Arabidopsis, the MwMYB-1 transcription factor preferred to bind the “AAGAGAG” motif (DREME-5) in the third exon of the AtMYB75 gene. The yeast one hybrid assay and transcription activity assay further confirmed this. Thus, MwMYB-1 activated AtMYB75 gene expression and conducted cascade amplification of anthocyanin biosynthesis. Taken together, our findings provide a novel understanding of anthocyanin biosynthesis regulation in M. wufengensis and can be used to promote agronomic trait improvement in tree species.

PbRVE6 Promotes Anthocyanins Accumulation in Pear Fruit Peel by Regulating Key Biosynthetic Genes.

Red peel color, a desirable trait in pears, is determined by anthocyanin accumulation. While REVEILLE (RVEs) transcription factors regulate anthocyanin biosynthesis in some plant species, their role in pear peel has not been well-studied. This study investigates the function of RVEs in anthocyanin biosynthesis in 'Zaosu' (low anthocyanin content) and its red bud mutant, 'Red Zaosu' (high anthocyanin content) fruit peel. Consistent with higher anthocyanin content, 'Red Zaosu' pears exhibited increased PbRVE6 expression compared to 'Zaosu', while PbRVE3a and PbRVE3b levels remained unchanged. Additionally, PbRVE6 was localized to the nucleus. Overexpression of PbRVE6 in 'Zaosu' pear pericarp significantly increased anthocyanin content and upregulated key anthocyanin pathway genes PbANS and PbUFGT. Conversely, VIGS silencing of PbRVE6 in 'Red Palacer' pears led to decreased expression of PbANS and PbUFGT and a slight reduction in anthocyanin content. Yeast one-hybrid and dual-luciferase assays confirmed that PbRVE6 can bind and activate the promoters of PbANS and PbUFGT. These findings demonstrate that PbRVE6 promotes anthocyanin accumulation in pear peel by directly regulating PbANS and PbUFGT expression. This study provides a valuable foundation for understanding the regulatory network of anthocyanins in pear peels, and offers potential genetic resources for the production of new pear germplasm.

A R2R3-MYB transcription factor, FeR2R3-MYB, positively regulates anthocyanin biosynthesis and drought tolerance in common buckwheat (Fagopyrum esculentum)

The R2R3-MYB transcription factors (TFs) play a crucial role in regulating plant secondary metabolism and abiotic stress responses, yet they are still poorly understood in common buckwheat (Fagopyrum esculentum), a valuable minor grain crop resource. In this study, a candidate gene, FeR2R3-MYB, was cloned from the anthocyanin-rich common buckwheat variety ‘QZZTQ’. FeR2R3-MYB was found to contain two MYB DNA-binding domains and be located at the nucleus with transcriptional activation activity. Molecular analysis indicated that FeR2R3-MYB is predominantly expressed in flowering tissue and is highly responsive to environmental factors such as light, drought, and cold. In addition, the promoter of FeR2R3-MYB showed a positive correlation with fragment length. Further functional analysis suggested that FeR2R3-MYB not only participates in the anthocyanin biosynthetic pathway by interacting with leucoanthocyanidin reductase (FeLAR), but also enhances drought tolerance in common buckwheat. To sum up, FeR2R3-MYB exhibits positive effects on both pigment production (e.g., anthocyanin) and abiotic stress resistance, providing valuable insights for future research in buckwheat molecular breeding and resource development.

R2R3-MYB repressor, BrMYB32, regulates anthocyanin biosynthesis in Chinese cabbage.

Anthocyanin-enriched Chinese cabbage has health-enhancing antioxidant properties. Although various regulators of anthocyanin biosynthesis have been identified, the role of individual repressors in this process remains underexplored. This study identifies and characterizes the R2R3-MYB BrMYB32 in Chinese cabbage (Brassica rapa), which acts as a repressor in anthocyanin biosynthesis. BrMYB32 expression is significantly upregulated under anthocyanin inductive conditions, such as sucrose and high light treatment. Transgenic tobacco plants overexpressing BrMYB32 show decreased anthocyanin levels and downregulation of anthocyanin biosynthesis genes in flowers, highlighting BrMYB32's repressive role. Located in the nucleus, BrMYB32 interacts with the TRANSPARENT TESTA 8 (BrTT8), a basic helix-loop-helix protein, but no interaction was detected with the R2R3-MYB protein PRODUCTION OF ANTHOCYANIN PIGMENT 1 (BrPAP1). Functional assays in Chinese cabbage cotyledons and tobacco leaves demonstrate that BrMYB32 represses the transcript level of anthocyanin biosynthesis genes, thereby inhibiting pigment accumulation. Promoter activation assays further reveal that BrMYB32 inhibits the transactivation of CHALCONE SYNTHASE and DIHYDROFLAVONOL REDUCTASE through the C1 and C2 motifs. Notably, BrMYB32 expression is induced by BrPAP1, either alone or in co-expression with BrTT8, and subsequently regulates the expression of these activators. It verifies that BrMYB32 not only interferes with the formation of an active MYB-bHLH-WD40 complex but also downregulates the transcript levels of anthocyanin biosynthesis genes, thereby fine-tuning anthocyanin biosynthesis. Our findings suggest a model in which anthocyanin biosynthesis in Chinese cabbage is precisely regulated by the interplay between activators and repressors.