Search Results (548)

Anthocyanins, a subclass of flavonoid pigments, impart vivid red, purple, and blue coloration to horticultural plants, playing essential roles in ornamental enhancement, stress resistance, and pollinator attraction. Recent studies have identified B-box (BBX) proteins as a critical class of transcription factors (TFs) involved in anthocyanin biosynthesis. Despite these advances, comprehensive reviews systematically addressing BBX proteins are urgently needed, especially given the complexity and diversity of their roles in regulating anthocyanin production. In this paper, we provide an in-depth overview of the fundamental structures, biological functions, and classification of BBX TFs, along with a detailed description of anthocyanin biosynthetic pathways and bioactivities. Furthermore, we emphasize the diverse molecular mechanisms through which BBX TFs regulate anthocyanin accumulation, including direct activation or repression of target genes, indirect modulation via interacting protein complexes, and co-regulation with other transcriptional regulators. Additionally, we summarize the known upstream regulatory signals and downstream target genes of BBX TFs, highlighting their significance in shaping anthocyanin biosynthesis pathways. Understanding these regulatory networks mediated by BBX proteins will not only advance fundamental horticultural science but also provide valuable insights for enhancing the aesthetic quality, nutritional benefits, and stress adaptability of horticultural crops. Full article

Anthocyanins, crucial water-soluble pigments in plants, determine coloration in floral and fruit tissues, while fulfilling essential physiological roles in terms of plant growth, development, and stress adaptation. The biosynthesis of anthocyanins is transcriptionally regulated by WRKY factors, one of the largest plant-specific transcription factor families. Euscaphis japonica is an East Asian species, prized for its exceptionally persistent butterfly-shaped fruits that undergo pericarp dehiscence, overturning, and a color transition to scarlet red. This species represents an ideal system for studying anthocyanin regulation. However, the mechanisms by which WRKY transcription factors orchestrate anthocyanin accumulation during this process remain unknown. In this study, we identified 87 WRKY genes (EjaWRKYs) from the E. japonica genome. Phylogenetic analysis was used to classify these genes into three primary groups, with five subgroups, revealing conserved gene structures and motif compositions, supported by collinearity and comparative synteny analyses. Crucially, ten EjaWRKYs exhibited peak expression during the mature fruit stages, showing positive correlations with key anthocyanin biosynthesis genes. Functional validation through the use of transient transactivation assays in Nicotiana benthamiana confirmed that the five selected EjaWRKYs bind W-box elements and strongly activate reporter gene expression. Our results reveal EjaWRKYs’ regulation of anthocyanin accumulation in E. japonica fruit, provide the first comprehensive WRKY family characterization of this species, and establish a foundation for manipulating ornamental traits in horticultural breeding. Full article

B-box (BBX) transcription factors are critical regulators of light-mediated anthocyanin biosynthesis, influencing peel coloration in plants. To explore their role in red mango cultivars, we identified 32 BBX genes (MiBBX1–MiBBX32) in the mango (Mangifera indica L.) genome using a genome-wide analysis. Phylogenetic and structural analyses classified these genes into five subfamilies based on conserved domains. A collinearity analysis revealed segmental duplication as the primary mechanism of MiBBX gene family expansion, with purifying selection shaping their evolution. A promoter analysis identified numerous light- and hormone-responsive cis-elements, indicating regulatory roles in the light and hormonal signaling pathways. Expression profiling in the ‘Sensation’ cultivar revealed organ-specific patterns, with several MiBBX genes showing higher expression in the peel than in the flesh. Many of these genes also consistently exhibited elevated expression in the peel of red-skinned cultivars (‘Sensation’ and ‘Guifei’) compared to yellow and green cultivars, suggesting their role in red peel pigmentation. Furthermore, postharvest light treatment of ‘Hongmang No. 6’ fruit significantly upregulated multiple MiBBX genes, suggesting their involvement in light-induced anthocyanin accumulation in red mango peel. These findings provide valuable insights into the molecular mechanisms governing light-regulated peel coloration in mango and establish a foundation for functional studies of MiBBX genes in fruit pigmentation. Full article

Anthocyanins are important phenolic compounds in grape skins, affecting the color, oxidation resistance, and aging ability of red wine. In recent years, global warming has had a negative effect on anthocyanin biosynthesis in grape berries. Ethylene serves as a crucial phytohormone regulating the development and ripening processes of fruit; however, the specific molecular mechanism and the regulatory network between ethylene signaling and the anthocyanin biosynthesis pathway remain incompletely understood. In this study, 400 mg/L ethephon (ETH) solution was sprayed onto the surface of grape berries at the lag phase (EL-34), and the changes in anthocyanin-related genes and metabolites were explored through transcriptomic and metabolomic analysis. The results showed that ETH treatment increased Brix and pH in mature berries. In total, 35 individual anthocyanins were detected, in which 21 individual anthocyanins were enhanced by ETH treatment. However, the anthocyanin profile was not affected by exogenous ethylene. Transcriptomics analysis showed that there were a total of 825 and 1399 differentially expressed genes (DEGs) 12 h and 24 h after treatment. Moreover, key structural genes in the anthocyanin synthesis pathway were strongly induced, including VvPAL, VvCHS, VvF3H, VvF3′5′H, VvDFR and VvUFGT. At the maturity stage (EL-38), the expression levels of these genes were still higher in EHT-treated berries than in the control. ETH treatment also influenced the expression of genes related to hormone biosynthesis and signal transduction. The ethylene biosynthesis gene (VvACO), ethylene receptor genes (VvETR2, VvERS1 and VvEIN4), ABA biosynthesis gene (VvNCED2), and ABA receptor gene (VvPYL4) were up-regulated by ETH treatment, while the auxin biosynthesis gene (VvTAA3) and seven genes of the auxin-responsive protein were inhibited by exogenous ethylene. Meanwhile, ETH treatment promoted the expression of the sugar transporter gene (VvEDL16) and two sucrose synthase genes (VvSUS2 and VvSUS6). In EHT-treated berries, 19 MYB and 23 ERF genes were expressed differently compared with the control (p < 0.05). This study provides the theoretical foundation and technical support for the regulation of anthocyanin synthesis in non-climacteric fruit. Full article

The establishment of a transient expression system in petals is significant for elucidating gene functions in flowering trees characterized by a prolonged juvenile phase. Genetic improvements in Camellia japonica have been hindered due to the absence of a functional validation platform. In this study, we explored an Agrobacterium-mediated and readily observable transient expression system in camellia petals to systematically optimize four critical factors affecting transformation efficiency. As a result, the bud stage, ‘Banliuxiang’ genotype, OD600 of 1.0, and 1-day co-cultivation achieved the highest intensity of transient expression, and overexpression of the Ruby1 reporter gene induced substantial anthocyanin synthesis, manifested as distinct red pigmentation. Furthermore, the optimized transient expression system revealed that the R2R3-MYB transcription factor CjMYB5, which interacted with CjGL3, promoted anthocyanin biosynthesis in camellia petals by transactivating key DFR structural genes. This transient expression platform not only advances functional genomics studies in ornamental woody species but also lays a foundation for molecular breeding programs in C. japonica. Full article

NAC (NAM, ATAF1/2, CUC1/2) is a plant-specific transcription factor (TF) family that plays important roles in various physiological and biochemical processes of plants. However, the NAC gene family in Lagerstroemia indica and its role in anthocyanin metabolism are still unexplored. In our study, a total of 167 NACs were identified in the L. indica genome via genome-wide analysis and bioinformatics techniques. Amino acid sequence analysis showed that all 167 NAC proteins contained a conserved NAM domain. This domain primarily comprised random coils, extended strands, and alpha helices. Most NACs were found on the nucleus and dispersed over 23 of the 24 plant chromosomes. Based on phylogenetic analysis, the NACs can be categorized into ten subgroups. Furthermore, the promoter homeotropic elements predicted the cis-acting elements in the promoters of these genes related to hormones, development, environmental stress response, and other related responses, demonstrating the diverse regulatory mechanisms underlying gene functions. In addition, a co-expression network was established through RNA sequencing. This network helped identify seven key LiNACs, genes related to anthocyanin expression (CHS) and transcription factors (MYB and bHLH). To identify potential anthocyanin regulatory factors present in L. indica petals, protein interaction prediction was performed, which revealed that LiNACs might participate in anthocyanin regulation by interacting with other proteins, such as MYB, ABF, ABI, bZIP, MYC, etc. Our results provided novel insights and could help in the functional identification of LiNACs in L. indica and the regulation of anthocyanin synthesis. Full article

Flavonoids play a crucial role in plant development, resistance, and the pigmentation of fruits and flowers. This study aimed to uncover the mechanism of flavonoid biosynthesis and fruit coloring in muscadine grapes. Two muscadine genotypes (Paulk and Supreme) were investigated via metabolomic and transcriptomic analysis during three developmental stages (bunch closure, veraison stage, and ripening stage). A total of 314 flavonoids were identified, with flavones and flavonols being the primary constituents. The contents of many differentially accumulated metabolites (DAMs) were higher at the veraison stage. The total anthocyanin content was upregulated during berry development, with the dominant type of anthocyanidin-3,5-O-diglucoside. Proanthocyanins accumulated higher levels in the ripening stage of Paulk than Supreme. Transcriptomic analyses revealed that over 46% of the DEGs exhibited higher expression levels in the bunch closure stage. Moreover, phenylalanine ammonia-lyase (PAL), cinnamyl 4-hydroxylase (C4H), and coumaryl CoA ligase (4CL) genes were upregulated during berry development, suggesting they promote second metabolites biosynthesis. The upregulation of dihydroflavonol 4-reductase (DFR) and leucoanthocyanin reductase (LAR) may related to the higher levels of PA in Paulk. Anthocyanidin synthase (ANS) and UDP-glucose:flavonoid-3-O-glucosyltransferase (UFGT) showed higher expression levels in the ripening stage, which may relate to the accumulation of anthocyanidins. This study provides comprehensive insights into flavonoid metabolism and berry coloration in Vitis rotundifolia. Full article

The occurrence of anthocyanins in rice (Oryza sativa) and barley (Hordeum vulgare) varies among cultivars, with pigmented varieties (e.g., black rice and purple barley) accumulating higher concentrations due to genetic and environmental factors. The biosynthesis of anthocyanins is regulated by a complex network of structural and regulatory genes. Key enzymes in the pathway include chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3-hydroxylase (F3H), dihydroflavonol 4-reductase (DFR), anthocyanidin synthase (ANS), and UDP-glucose flavonoid 3-O-glucosyltransferase (UFGT). These genes are tightly controlled by transcription factors (TFs) from the MYB, bHLH (basic helix–loop–helix), and WD40 repeat families, which form the MBW (MYB-bHLH-WD40) regulatory complex. In rice, OsMYB transcription factors such as OsMYB3, OsC1, and OsPL (Purple Leaf) interact with OsbHLH partners (e.g., OsB1, OsB2) to activate anthocyanin biosynthesis. Similarly, in barley, HvMYB genes (e.g., HvMYB10) coordinate with HvbHLH TFs to regulate pigment accumulation. Environmental cues, such as light, temperature, and nutrient availability, further modulate these TFs, influencing the production of anthocyanin. Understanding the genetic and molecular mechanisms behind the biosynthesis of anthocyanins in rice and barley provides opportunities for the development of biofortification strategies that enhance their nutritional value. Full article

Flavonoids are an important type of bioactive substance contained in jujubes. Flavonol synthase (FLS) is a key enzyme for the synthesis of flavonoids such as flavonols and anthocyanins. To study the biological functions of FLS in jujubes, we cloned the ZjFLS gene; analyzed its physicochemical properties and evolutionary relationships; and then conducted an expression characteristic analysis, subcellular localization, prokaryotic expression and heterologous overexpression in Arabidopsis thaliana. The results showed that the length of ZjFLS is 951 bp, and it encodes 316 amino acids. A sequence analysis revealed that ZjFLS exhibited a high degree of conservation in evolution. The results of a qRT-PCR analysis indicated that the ZjFLS gene could be expressed in different tissues of jujube: the expression level was the highest in the leaves, followed by the flowers, and the lowest was in the fruits. Within these expression levels, it was higher in young leaves than in mature leaves and higher in the white-ripe-stage fruits than in the semi-red-stage fruits. Subcellular localization indicated that the ZjFLS gene was located in the nucleus, cytoplasmic matrix, and cytoplasmic membrane. Our research findings show that the ZjFLS protein can be induced and obtained in the prokaryotic expression system and successfully purified. It mainly exists in the form of inclusion bodies and has a relatively low content in the soluble supernatant. The total flavonoid content of Arabidopsis thaliana strains with a heterologous overexpression of the ZjFLS gene was significantly higher than that of the wild type, confirming that the ZjFLS gene can promote the biosynthesis of flavonoid substances. Full article

The AP2/ERF transcription factor ABSCISIC ACID INSENSITIVE 4 (ABI4) plays diverse roles in plant development and responses to abiotic stress. However, its potential involvement in regulating anthocyanin biosynthesis is not fully understood. In this study, three different loss-of-function abi4 alleles (abi4-1, abi4-2, and abi4-101) were employed to investigate the role of ABI4 in the regulation of anthocyanin accumulation in Arabidopsis seedlings. These abi4 mutants exhibited significantly increased anthocyanin accumulation, which was associated with elevated expression of genes involved in anthocyanin biosynthesis. HY5 (LONG HYPOCOTYL 5), a central component of photomorphogenesis, acts as a key light-regulated molecular switch. Further analysis revealed that ABI4 requires HY5 to function as a negative regulator of anthocyanin biosynthesis. Additionally, loss of ABI4 resulted in heightened light sensitivity, leading to increased light-induced chlorophyll accumulation and chloroplast development, along with upregulation of photosynthesis-related genes. Interestingly, the light-hypersensitive phenotype of abi4 mutants was partially rescued by the loss of HY5 function. Taken together, these findings demonstrate that ABI4 negatively regulates anthocyanin accumulation in Arabidopsis seedlings through a HY5-dependent light signaling pathway. Full article

Phalaenopsis pulcherrima are known for their captivating floral morphology and diverse colors, demonstrate exceptional resilience to adverse environmental conditions, and exhibit significant potential for hybrid breeding. However, current research on flower coloration is still limited. The data from this study indicates that variations in anthocyanin levels are the primary determinants of the difference between white and purple colors. Through RNA-seq, we identified 469 genes that were differentially expressed. Furthermore, our bioinformatics exploration uncovered two potential transcription factors, PpMYB1 and PpbHLH1, which play regulatory roles in anthocyanin accumulation. Y2H assays demonstrated that these two TFs could form heterodimers and interact with each other. Afterwards, transient expression assays were conducted for the first time in P. pulcherrima flowers, revealing that overexpression of PpMYB1 alone or in combination with PpbHLH1 resulted in purple petal pigmentation. Overexpressing PpMYB1 in tobacco resulted in more purple-colored corollas, stamens, pistils, and pods compared to control plants. Y1H and dual-luciferase assays provided further evidence that PpMYB1 and PpbHLH1 interact with the promoters of the structural genes PpF3H, PpDFR, and PpANS in the anthocyanin biosynthesis pathway, thereby driving their robust expression. This study not only enhances our understanding of the molecular mechanisms underlying anthocyanin synthesis but also holds significant practical implications for advancing plant hybrid breeding and genetic engineering applications in flower color regulation. Full article

The transition to ripening in non-climacteric species is governed by several signals, including hormones that enhance or counteract the abscisic acid (ABA)-promoting effect. The SQUAMOSA Promoter-binding protein-Like (SPL) transcription factors are involved in ripening through the modulation of anthocyanin biosynthesis. In sweet cherry fruits, several miR156-targeted PavSPLs are expressed before and during ripening. Recently, some PavSPLs were found in the transition from development to ripening in cultivars contrasting in maturity time. Additionally, several forms of miR156 were expressed in sweet cherry seeds of an early-season cultivar. In this work, we addressed the relevance of endocarp lignification and PavSPLs expression for the transition to ripening. First, we characterized early- and late-season sweet cherry cultivars, ‘Celeste’ and ‘Regina’, focusing on fruit and seed development, endocarp lignification, and PavSPL expression profile. Fruit growth dynamics revealed an earlier onset of color development and lignification in ‘Celeste’, while ‘Regina’ exhibited a prolonged lag phase and delayed embryo development. Transcript profiling at the light green stage showed a higher expression of PavSPL genes in fruits and identified cultivar-specific expressions, especially between ‘Regina’ and ‘Celeste’ seeds. Co-expression networks linked PavSPLs to genes involved in lignin and anthocyanin biosynthesis. We focused on PavSPL2 and PavSPL9, which were targeted by mtr-miR156a and gma-miR156f. Both PavSPLs and miRNAs were expressed in fruits and seeds at the yellow stage, an advanced point in the transition to ripening in sweet cherry. Exogenous application of auxin-related compounds in the mid-season cultivar ‘Lapins’ modulated endocarp lignification and pigmentation. Notably, p-IBA treatment, which enzymatically targets the lignin pathway, transiently increased anthocyanin accumulation and reduced lignin deposition, effects that correlated with the downregulation of PavSPL gene expression. These findings highlight the interplay between lignification, color evolution, and pigment biosynthesis during the transition from development to ripening in sweet cherry fruits, and suggest a role for PavSPL genes in this transition. Full article

The basic leucine zipper (bZIP) gene family constitutes one of the most abundant and conserved transcription factor families in plants, which participates in diverse physiological processes including response to abiotic stress, anthocyanin accumulation, and the regulation of plant growth and development. Although bZIP genes play an important role in plants, comparable studies in mulberry are lacking, particularly regarding their response under abiotic stress conditions. In this study, we identified 56 mulberry bZIP transcription factors and divided these members into 12 groups by phylogenetic analysis. The coding genes of these bZIPs harbor a large number of segmental duplications and are unevenly distributed on 12 chromosomes. We further identified numerous stress responsive elements in the promoter regions of bZIP genes. Furthermore, by analysis of the expression profiles from RNA-seq data, we identified MabZIP43 and MabZIP24 that respond to heat, salt–alkaline, and high light stress. We also found that the gene expression of MabZIP16 was closely related to anthocyanin biosynthesis. As described, we systematically explored the structures and functions of the bZIP gene family in Morus alba. The results imply that the bZIP gene family plays significant roles in stress response and anthocyanin biosynthesis. Three bZIP candidate genes are suggested for genetic engineering to improve the resistance of mulberry to stress and for high-anthocyanin-producing lines. Full article

Flavonoids are a class of secondary metabolites synthesized by plants, characterized by a C6-C3-C6 carbon skeleton and derived from the phenylpropane metabolism pathway. They play crucial biological roles, not only in plant pigment production and responses to biotic and abiotic stresses but also in medicinal applications. Consequently, the biosynthesis and regulatory mechanisms of flavonoids have been a focal point in plant transcription and gene expression research. The biosynthetic pathways of flavonoids include branches such as isoflavones, flavones, flavonols, anthocyanins, and proanthocyanidins, with some pathways and key enzymes already well-characterized. Studies indicate that plant flavonoids are regulated by various factors, including transcription factors, non-coding endogenous small RNAs (miRNAs), and plant hormones. This review systematically summarizes the structure and classification of plant flavonoids, their biosynthetic and regulatory mechanisms, and the factors influencing flavonoid synthesis. By discussing the regulation of flavonoid-related gene expression in plants, this work provides valuable insights and a theoretical foundation for future research and applications of flavonoids. Full article

Fruit color is a key indicator of appearance quality. Anthocyanins are flavonoids that not only give plants their rich colors but also contribute to human health due to their antioxidant properties, such as preventing cardiovascular disease. As a result, fruits with high anthocyanin content are becoming increasingly popular in the market. Anthocyanin biosynthesis is regulated by various genetic, developmental, and environmental factors, primarily through physiological and biochemical metabolism, as well as the expression of structural and regulatory genes. This review explores how environmental factors and phytohormones jointly regulate anthocyanin biosynthesis, thereby providing strategies to produce high quality fruits. Focusing on major environmental factors and hormonal signaling, this review summarizes current knowledge on the transcriptional networks that regulate anthocyanin biosynthesis, with particular emphasis on the crosstalk between these regulatory factors. Full article