The MYB transcription factor RcMYB1 plays a central role in rose anthocyanin biosynthesis

A Key R2R3-MYB Transcription Factor Activates Anthocyanin Biosynthesis and Leads to Leaf Reddening in Poplar Mutants

Colorful woody plants are highly valued for their ornamental qualities, and are commonly used in garden landscape design. We previously cultivated several ornamental poplar varieties from bud mutants of Populus sp. Linn. '2025' (ZL2025), each with different leaf colors. Based on transcriptome data from these varieties with varying anthocyanin pigmentation, we identified and named an R2R3-MYB gene, PdMYB113. The mRNA of PdMYB113 accumulated in the leaves of the red-leaf mutants 'QHY' and 'LHY', but barely expressed in the leaves of 'ZL2025'. The anthocyanin biosynthesis genes were upregulated, resulting in high levels of red anthocyanins (particularly Peonidin-3-O-rutinoside, Cyanidin-3-O-rutinoside, and Cyanidin-3-O-glucoside) in both OE-PdMYB113 tobacco and poplar plants. This upregulation caused a color change in the tissues from green to red or dark purple. Yeast one-hybrid and luciferase assays demonstrated that PdMYB113 activates the expression of anthocyanin biosynthesis genes, including the early anthocyanin biosynthetic gene PdCHS and the late anthocynin biosynthetic gene PdANS. Consequently, PdMYB113 is identified as a key regulator of red coloration in poplar. Additionally, PdMYB113 does not dwarf transgenic plants under normal lighting conditions. This study elucidates the regulatory mechanisms of color change in ZL2025 and highlights a crucial gene for breeding new varieties of woody plants.

Targeted metabolite and molecular profiling of carotenoids in rose petals: A step forward towards functional food applications

Given the increasing consumer demand for natural and functional foods, rose petals offer a promising novel ingredient for food innovation, especially yellow and orange rose petals rich in carotenoids, making them ideal for food processing and color retention. Despite their potential, the metabolic profile of carotenoids in roses has not yet been fully explored. Therefore, the present study aimed to provide a comprehensive analysis of carotenoid metabolism in rose petals during three developmental stages. The results revealed that orange rose petals had the highest carotenoid content of 488.85 μg/g, with xanthophylls being identified as the primary carotenoid constituents (70.40 %) in roses for the first time. Furthermore, two genes, RhBCH1 and RhCCD4, were identified to be involved in the regulation of carotenoid biosynthesis in roses. Overall, this study demonstrates the enormous potential of rose petals as functional food ingredients, providing a theoretical basis for breeding high-carotenoid rose varieties.

The candidate gene SibHLHA regulates anthocyanin-driven purple pigmentation in Sesamum indicum flowers

Anthocyanins not only serve as critical pigments determining floral hues but also play essential roles in attracting insects for pollination, feeding animals and mitigating abiotic stress. However, the molecular mechanisms underlying the regulation of flower color in sesame has not yet been reported. In this study, an F2 population was constructed by crossing 'Ganzhi 9' (purple-flowered) with 'BS377' (white-flowered). Genetic analysis revealed that purple flower is controlled by a single locus named as SiFC (Sesamum indicum flower color). Using the BSA-seq approach, SiFC was preliminarily identified on chromosome 6, which was further mapped to a 473 kb interval using Kompetitive Allele Specific PCR (KASP) marker analysis. Moreover, functional annotation, expression profiling, and sequence analyses confirmed that the SibHLHA (Sesame10992) was the most likely candidate gene for SiFC. In addition, SibHLHA, highly homologous to AtTT8 (a key regulator in the anthocyanin synthesis pathway), was found to interact with WER-like or TTG1 proteins, enhancing anthocyanin accumulation in tobacco leaves. Furthermore, an SNP in the second exon of Sibhlha (BS377 variant) was found to alter the encoding amino acids, which affected Sibhlha binding to MYB protein and showed low anthocyanin in tobacco leaves compared with SibHLHA binding with WER-like or TTG1 proteins. These findings not only deepen our understanding of the molecular mechanisms controlling sesame corolla color, but also provide valuable insights for developing ornamental and consumable sesame varieties.

The bHLH transcription factor DlbHLH68 positively regulates DlSPS1 expression to promote sucrose biosynthesis in longan

Sucrose is an important factor affecting plant growth and fruit quality, but the molecular regulatory mechanism of sucrose biosynthesis in longan is not yet understood. Here, we characterized a transcription factor, DlbHLH68, positively regulates sucrose accumulation in longan. Subcellular localization and transcriptional activity analysis indicated that DlbHLH68 is a nuclear transcriptional activator. Overexpressing DlbHLH68 in Arabidopsis enhanced sucrose content, plant height, and the relative expression level of sucrose phosphate synthase genes (AtSPS1 and AtSPS2). Yeast one-hybrid and dual-luciferase reporter assays indicated that DlbHLH68 was able to activate the expression of DlSPS1, the homology gene of AtSPS1. As expected, overexpression of DlSPS1 significantly increased the sucrose content in transgenic Arabidopsis and longan fruits. Collectively, this study reveals that DlbHLH68 is a positive regulator in sucrose accumulation by activating DlSPS1 expression to mediate sucrose biosynthesis, which is helpful for understanding the molecular basis of sucrose biosynthesis and accumulation in longan fruit and provides candidate genes for further breeding.

Integrated Transcriptomic and Metabolomic Analysis Revealed Regulatory Mechanisms on Flavonoids Biosynthesis in the Skin of Passion Fruit (Passiflora spp.)

Passion fruit is one of the most famous fruit crops in tropical and subtropical regions due to its high edible, medicinal, and ornamental value. Flavonoids, a class of plant secondary metabolites, have important health-related roles. In this study, a total of 151 flavonoid metabolites were identified, of which 25 key metabolites may be the main contributors to the purple phenotype. Using RNA sequencing, 11,180 differentially expressed genes (DEGs) were identified. Among these, 48 flavonoid biosynthesis genes (PAL, 4CL, C4H, CHS, CHI, F3H, DFR, ANS, and UFGT) and 123 transcription factors were identified. Furthermore, 12 distinct modules were identified through weighted gene coexpression network analysis, of which the brown module displays a robust positive correlation with numerous flavonoid metabolites. Overexpression of PeMYB114 significantly promoted flavonoids accumulation in tobacco leaves. Our study provided a key candidate gene for molecular breeding to improve color traits in passion fruit.

From White to Reddish-Brown: The Anthocyanin Journey in Stropharia rugosoannulata Driven by Auxin and Genetic Regulators

Stropharia rugosoannulata, or wine-cap Stropharia, is a well-known edible mushroom cultivated globally. The pileipellis color is a crucial quality attribute of S. rugosoannulata, exhibiting significant variation throughout its developmental stages. However, the pigment types and regulatory mechanisms behind color variation remain unclear. The metabolome analysis found that the anthocyanin biosynthesis pathway was significantly enriched and anthocyanins accumulated steadily in fruiting bodies during three developmental stages. The pileipellis pigment was extracted, and HPLC-MS confirmed the presence of anthocyanins. Notably, significant differences in anthocyanin content were observed among the various colored varieties. Thus, anthocyanins contribute to the pileipellis color of S. rugosoannulata. Through further investigation, this study elucidated, for the first time, the relationship between the "SrNFYA-SrDRF2" regulatory module and anthocyanin accumulation. Combined multiomics assays and HPLC analysis revealed that auxin functions as a signaling molecule that regulates the accumulation of anthocyanins in the pileipellis. Subsequently, the hub gene of anthranilate synthase for auxin synthesis was identified as SrTRP1, and the transcription factor SrMYB1 was verified as a regulator of SrTRP1, influencing auxin accumulation. These findings provide a valuable resource for the targeted enhancement of the quality of S. rugosoannulata.

MsMYB206-MsMYB450-MsHY5 complex regulates alfalfa tolerance to salt stress via regulating flavonoid biosynthesis during the day and night cycles

Flavonoids are the major secondary metabolites participating in many biological processes of plants. Although flavonoid biosynthesis has been extensively studied, its regulatory mechanisms during the day and night cycles remain poorly understood. In this study, three proteins, MsMYB206, MsMYB450, and MsHY5, were found to interact with each other, in which MsMYB206 directly transactivated two flavonoid biosynthetic genes, MsFLS and MsF3'H. The expression patterns of MsMYB206, MsMYB450, MsFLS, and MsF3'H were fully consistent at regular intervals across day/night cycles that were higher at night than in the daytime. On the contrary, both gene expression levels and protein contents of MsHY5 increased in the daytime but decreased at night, and the lower expression of MsHY5 at night led to strengthened interaction between MsMYB206 and MsMYB450. The MsMYB206-overexpression plants were more salt-tolerant and their flavonoid contents were higher than the WT during the day/night cycles. This study revealed one mechanism interpreting the fluctuating flavonoid contents during day/night cycles regulated by the MsMYB206/MsMYB450/MsHY5-MsFLS/MsF3'H module that also contributed to salt tolerance in alfalfa.

MsMYB62-like as a negative regulator of anthocyanin biosynthesis in Malus spectabilis

Crabapple is a valuable tree species in gardens due to its captivating array of flower and leaf colors, rendering it a favored choice in landscaping. The economic and ornamental values of Malus crabapple are closely associated with the biosynthesis of anthocyanin, a pigment responsible for its vibrant hues. The intricate regulation of anthocyanin biosynthesis involves the concerted activity of various genes. However, the specific mechanism governing this process in crabapple warrants in-depth exploration. In this study, we explored the inhibitory role of MsMYB62-like in anthocyanin biosynthesis. We identified MsDFR and MsANS as two downstream target genes of MsMYB62-like. These genes encode enzymes integral to the anthocyanin biosynthetic pathway. The findings demonstrate that MsMYB62-like directly binds to the promoters of MsDFR and MsANS, resulting in the downregulation of their expression levels. Additionally, our observations indicate that the plant hormone cytokinins exert a suppressive effect on the expression levels of MsMYB62-like, while concurrently upregulating MsDFR and MsANS. This study reveals that the MsMYB62-like-MsDFR/MsANS module plays an important role in governing anthocyanin levels in Malus crabapple. Notably, the regulatory interplay is modulated by the plant hormone cytokinins.

Rosa rugosa R2R3-MYB transcription factors RrMYB12 and RrMYB111 regulate the accumulation of flavonols and anthocyanins

Roses (Rosa rugosa) are a famous flower with high ornamental and economic value. But the petals of roses are usually pink and purple, which restricted its application in garden settings. Flavonols and anthocyanins are crucial secondary metabolites related to flower pigmentation in plants. While MYB transcription factors involved in the biosynthesis pathway of anthocyanins have been identified in roses, the functional characterization of the MYB transcription factor regulating flavonol synthesis in R. rugosa remains unexplored. In this study, we isolated and characterized the R2R3-MYB transcription factors RrMYB12 and RrMYB111 involved in regulation of the flavonol biosynthetic pathway from R. rugosa. The bioinformatics analysis indicated that both the RrMYB12 and RrMYB111 belong to the R2R3-MYB subgroup 7 family. qRT-PCR analysis showed that RrMYB12 and RrMYB111 were expressed at low levels in roots and flowers. And transactivation activity assay indicated that RrMYB12 and RrMYB111 were transcriptional activators. The overexpression of RrMYB12 and RrMYB111 in tobacco resulted in an elevation of flavonol levels and a reduction in anthocyanin levels in flowers due to the upregulation of structural genes involved in flavonol synthesis, while the biosynthesis genes for the anthocyanin pathway were significantly downregulated. The transient reporter assay demonstrated that RrMYB12 exhibited strong activation of the promoters of RrCHS and RrFLS in Nicotiana benthamiana leaves following transient transformation. Furthermore, it was observed that RrMYBs displayed binding specificity to the promoter region of CsFLS.The functional characterization of the flavonol synthesis regulatory factors RrMYB12 and RrMYB111 offers a deeper understanding of the regulatory mechanism governing flavonol biosynthesis in roses, while also presenting an effective tool for genetic manipulation aimed at creating new varieties.

TRANSPARENT TESTA 16 collaborates with the MYB-bHLH-WD40 transcriptional complex to produce brown fiber cotton

Naturally colored cotton (NCC; Gossypium spp.) does not require additional chemical dyeing and is an environmentally friendly textile material with great research potential and applications. Our previous study using linkage and association mapping identified TRANSPARENT TESTA 2 (Gh_TT2) as acting on the proanthocyanin synthesis pathway. However, limited information is available about the genetic regulatory network of NCC. Here, we verified the effectiveness of Gh_TT2 and the roles of Gh_TT2 and red foliated mutant gene (Re) in pigment formation and deposition of brown fiber cotton (BFC). Variations in Gh_TT2 derived from interspecific hybridization between Gossypium barbadense acc. Pima 90-53 and Gossypium hirsutum acc. Handan208 resulted in gene expression differences, thereby causing phenotypic variation. Additionally, the MYB-bHLH-WD complex was found to be negatively modulated by TRANSPARENT TESTA 16/ARABIDOPSIS BSISTER (TT16/ABS). RNA-seq suggested that differential expression of homologous genes of key enzymes in the proanthocyanin synthesis pathway strongly contributes to the color rendering of natural dark brown and light brown cotton. Our study proposes a regulatory model in BFC, which will provide theoretical guidance for the genetic improvement of NCC.

The evaluation of transcription factor binding site prediction tools in human and Arabidopsis genomes

BACKGROUND

The precise prediction of transcription factor binding sites (TFBSs) is pivotal for unraveling the gene regulatory networks underlying biological processes. While numerous tools have emerged for in silico TFBS prediction in recent years, the evolving landscape of computational biology necessitates thorough assessments of tool performance to ensure accuracy and reliability. Only a limited number of studies have been conducted to evaluate the performance of TFBS prediction tools comprehensively. Thus, the present study focused on assessing twelve widely used TFBS prediction tools and four de novo motif discovery tools using a benchmark dataset comprising real, generic, Markov, and negative sequences. TFBSs of Arabidopsis thaliana and Homo sapiens genomes downloaded from the JASPAR database were implanted in these sequences and the performance of tools was evaluated using several statistical parameters at different overlap percentages between the lengths of known and predicted binding sites.

RESULTS

Overall, the Multiple Cluster Alignment and Search Tool (MCAST) emerged as the best TFBS prediction tool, followed by Find Individual Motif Occurrences (FIMO) and MOtif Occurrence Detection Suite (MOODS). In addition, MotEvo and Dinucleotide Weight Tensor Toolbox (DWT-toolbox) demonstrated the highest sensitivity in identifying TFBSs at 90% and 80% overlap. Further, MCAST and DWT-toolbox managed to demonstrate the highest sensitivity across all three data types real, generic, and Markov. Among the de novo motif discovery tools, the Multiple Em for Motif Elicitation (MEME) emerged as the best performer. An analysis of the promoter regions of genes involved in the anthocyanin biosynthesis pathway in plants and the pentose phosphate pathway in humans, using the three best-performing tools, revealed considerable variation among the top 20 motifs identified by these tools.

CONCLUSION

The findings of this study lay a robust groundwork for selecting optimal TFBS prediction tools for future research. Given the variability observed in tool performance, employing multiple tools for identifying TFBSs in a set of sequences is highly recommended. In addition, further studies are recommended to develop an integrated toolbox that incorporates TFBS prediction or motif discovery tools, aiming to streamline result precision and accuracy.

Epigenetic Regulation of Anthocyanin Biosynthesis in Betula pendula 'Purple Rain'

Betula pendula 'Purple Rain' is characterized by its purple leaves and has ornamental applications. A green mutant line NL, which was mutated by line NZ of B. pendula 'Purple Rain' during tissue culture, shows green leaves instead of the typical purple color of B. pendula 'Purple Rain'. This study quantified the leaf color traits of NL and a normal B. pendula 'Purple Rain' line NZ, and uncovered differentially expressed genes involved in flavonoid biosynthesis pathway genes in NL through RNA-Seq analysis. Compared to NZ, reduced levels of six anthocyanins contained in NL were revealed via flavonoids-targeted metabolomics. Sequence mutations in transcription factors that could explain NL's phenotype failed to be screened via whole-genome resequencing, suggesting an epigenetic basis for this variant. Therefore, a key gene, BpMYB113, was identified in NL via the combined analysis of small RNA sequencing, whole-genome methylation sequencing, and transcriptomics. In NL, this gene features a hyper CHH context methylation site and a lower transcription level compared to NZ, disrupting the expression of downstream genes in the phenylalanine metabolism pathway, and thereby reducing flavonoid biosynthesis. Our study elucidates an epigenetic mechanism underlying color variation in variegated trees, providing pivotal insights for the breeding and propagation of colored-leaf tree species.

Multiomics analysis reveals the involvement of OnDIVARICATA 3 in controlling dynamic flower coloring of Oncidium hybridum

Flower color is one of the main quality and economic traits of ornamental plants, and a large amount of research on flower color mainly focuses on the differences between varieties, while there were few reports on the change of flower color at different developmental stages. In this study, the metabolome and transcriptome of a new strain 'XM-1' with dynamic color changes of Oncidium were analyzed. The results showed that rutin, quercetin and carotenoids metabolism decreased significantly during the change of color from yellow to white. Analyzing the correlation network between metabolites and differential expressed genes, 25 key structural genes were detected and regulated by multiple MYB-related transcription factors. The MYB-related transcription factor Cluster-100966.1_OnDIVARICATA 3 was selected for further analysis. The phylogenetic tree of DIVARICATA in different species of Orchidaceae and Arabidopsis thaliana was constructed and the most closely related members were selected for sequence comparison. The results showed that OnDIVARICATA 3 contained MYB-like conserved domains. Subcellular localization results showed that OnDIVARICATA 3 was located in the nucleus. In overexpressing OnDIVARICATA 3 transgenic hairy roots, the expression of flower color related genes FLS, ZEP, and CHYB were significantly up-regulated. In summary, this study characterized the key metabolic pathways in the formation of the dynamic flower color of Oncidium hybridum, and constructed the regulatory network of the MYB-related. These results laid a theoretical foundation for the subsequent research on flower color and genetic engineering technology breeding of Oncidium hybridum.

Heterologous Expression of MYB Gene (Rosea1) or bHLH Gene (Delila) from Antirrhinum Increases the Phenolics Pools in Salvia miltiorrhiza

Phenolic acids have health-promoting properties, however, but their low concentrations in Salvia miltiorrhiza limit broader medicinal applications. MYB and bHLH transcription factors activate multiple target genes involved in phenylpropanoid metabolism, thereby enhancing the production of various secondary metabolites. We introduced the MYB transcription factor Antirrhinum Rosea1 (AmROS1) or Delila (AmDEL) into S. miltiorrhiza and observed that antioxidant activity in transgenic plants increased by 1.40 to 1.80-fold. The total content was significantly higher in transformants compared to the controls. Furthermore, heterologous expression of AmROS1 or AmDEL triggered moderate accumulations of rosmarinic acid and salvianolic acid at various growth stages. Levels of total phenolics, total flavonoids, and anthocyanins were significantly elevated. These biological and phytochemical alterations were correlated with the upregulated expression of genes involved in phenolic acid biosynthesis. Our findings demonstrate that AmROS1 and AmDEL function as a transcriptional activator in phenolic acids biosynthesis. This study offers further insights into the heterologous or homologous regulation of phenolics production, potentially enabling its engineering in S. miltiorrhiza.

Synergistic actions of 3 MYB transcription factors underpin blotch formation in tree peony

Blotches in floral organs attract pollinators and promote pollination success. Tree peony (Paeonia suffruticosa Andr.) is an internationally renowned cut flower with extremely high ornamental and economic value. Blotch formation on P. suffruticosa petals is predominantly attributed to anthocyanin accumulation. However, the endogenous regulation of blotch formation in P. suffruticosa remains elusive. Here, we identified the regulatory modules governing anthocyanin-mediated blotch formation in P. suffruticosa petals, which involves the transcription factors PsMYB308, PsMYBPA2, and PsMYB21. PsMYBPA2 activated PsF3H expression to provide sufficient precursor substrate for anthocyanin biosynthesis. PsMYB21 activated both PsF3H and PsFLS expressions and promoted flavonol biosynthesis. The significantly high expression of PsMYB21 in nonblotch regions inhibited blotch formation by competing for anthocyanin biosynthesis substrates, while conversely, its low expression in the blotch region promoted blotch formation. PsMYB308 inhibited PsDFR and PsMYBPA2 expressions to directly prevent anthocyanin-mediated blotch formation. Notably, a smaller blotch area, decreased anthocyanin content, and inhibition of anthocyanin structural gene expression were observed in PsMYBPA2-silenced petals, while the opposite phenotypes were observed in PsMYB308-silenced and PsMYB21-silenced petals. Additionally, PsMYBPA2 and PsMYB308 interacted with PsbHLH1-3, and their regulatory intensity on target genes was synergistically regulated by the PsMYBPA2-PsbHLH1-3 and PsMYB308-PsbHLH1-3 complexes. PsMYB308 also competitively bound to PsbHLH1-3 with PsMYBPA2 to fine-tune the regulatory network to prevent overaccumulation of anthocyanin in blotch regions. Overall, our study uncovers a complex R2R3-MYB transcriptional regulatory network that governs anthocyanin-mediated blotch formation in P. suffruticosa petals, providing insights into the molecular mechanisms underlying blotch formation in P. suffruticosa.

Unravelling the physiological and molecular mechanisms of leaf color change in Acer griseum through multi-omics analysis

Paperbark maple (Acer griseum), an endemic and endangered wild plant in China, has red-colored autumn leaves of high ornamental and garden application value. Leaf color change serves as a crucial indicator for evaluating garden tree aesthetics; however, research on A. griseum's leaf color change remains limited. This study aims to elucidate the physiological and molecular mechanisms underlying leaf color change in maple leaves through physiological, transcriptional, and metabolic assays. Data analysis encompasses gene expression levels and metabolite changes in three distinct states of maple leaves: green, half-red, and red. The progessive decrease of chlorophyll and carotenoids and the continuous accumulation of anthocyanidins caused a sharp change in leaf coloration, which was most drastic in the green to half-red period. Subsequently, targeted metabolomics analysis was performed, and a total of 71 anthocyanidins were detected, and the content of eight types of anthocyanidins increased significantly in the half-red and red periods, compared with that in the green period; of which the multiplicative difference was the largest for cyanidin-3,5-O diglucoside, delivering the largest multiplicative difference. Thus, it was plausible that cyanidin-3,5-O-diglucoside-dominated compoundswere likely to be the main metabolites associated with leaf reddening. Correlation analysis revealed that 12 key transcription factors (TFs) were significantly correlated with the anthocyanin-related metabolites and structural genes, which play important regulatory roles during the biosynthesis of anthocyanosides in A. griseum. These findings offered useful insights into the molecular basis of leaf color variation in A. griseum; providing valuable information to guide targeted genetic breeding and varietal improvement strategies.

Genome-wide analysis of the R2R3-MYB gene family and identification of candidate genes that regulate isoflavone biosynthesis in red clover (Trifolium pratense)

Red clover (Trifolium pratense) is a perennial legume with high feeding and medicinal value attributed to its abundant isoflavone content. Previous studies reported that R2R3-MYB transcription factors are involved in the biosynthesis of isoflavones; however, their specific role in red clover remains poorly understood. Through comprehensive genome-wide and transcriptome analyses, a total of 138 TpR2R3-MYB genes were identified and classified into 30 distinct subgroups within a phylogenetic tree. Importantly, six of these subgroups showed associations with isoflavone biosynthesis in red clover. The majority of segmental duplication events (Ka/Ks < 1) indicated that the TpR2R3-MYB gene underwent strong purifying selection during evolution. The qRT-PCR analysis demonstrated high expression levels of TpMYB79 and TpMYB53 in Minshan red clover at full flowering stage, consistent with the trend for isoflavone content determination, suggesting that TpMYB79 and TpMYB53 might be important regulators of isoflavone biosynthesis in red clover. Additionally, we observed nucleus and vacuole membrane localization of TpMYB53 and TpMYB79, with TpMYB53 primarily exerting transcriptional activation through its C-terminal activation motifs while TpMYB79 exhibited no transcriptional activity. These findings provided a foundation for the study of the biological function of R2R3-MYB transcription factors in red clover.

Transcriptomic and metabolomic analyses reveal molecular and metabolic regulation of anthocyanin biosynthesis in three varieties of currant

Anthocyanins are natural plant metabolites that are beneficial for human health. In order to study the fruit coloring mechanism mediated by anthocyanin biosynthesis in three currant varieties (white currant, red currant and black currant), we used a combination of transcriptomics and metabolomics analyses. Our comprehensive examination revealed that anthocyanins play a pivotal role in regulating the red and purple hues of black currant and red currant fruits. Specifically, Delphinidin-3-O-rutinoside, Pelargonidin-3-O-rutinoside, Cyanidin-3-O-rutinoside, Cyanidin-3,5-O-diglucoside, Cyanidin-3-O-rutinoside-5-O-glucoside and Petunidin-3-O-glucoside emerged as key anthocyanins in black currant, while Cyanidin-3-O-rutinoside (Keracyanin), Cyanidin-3-O-sambubioside[Cyanidin-3-O-(2″-O-xylosyl)glucoside], Cyanidin-3-O-glucoside (Kuromanin) and Cyanidin-3-O-(2″-O-xylosyl)rutinoside were identified as crucial anthocyanins in red currant. Transcriptomic data showed that the upregulation of dihydroflavonol 4-reductase (DFR), anthocyanin synthase (ANS), and UDP-glucose-flavonoid-3-O-glucosyltransferase (UFGT) genes significantly promoted the purple coloration of black currant fruit, while increased expression of Chalcone synthase (CHS) and flavonoid 3'-hydroxylase (F3'H) genes significantly intensified the red hue of red currant fruit. Furthermore, through weighted gene co-expression network analysis (WGCNA), we identified 11 transcription factors, including 3 bHLH, 2 MYB, 3 bZIP and 3 WRKY genes, which may serve as key regulators of anthocyanin biosynthesis. These findings provide a foundational understanding of the color dynamics in different currant varieties fruits throughout their developmental stages.

PhAN2 regulated Ph3GT silencing changes the flower color and anthocyanin content in petunias

Anthocyanins are important secondary metabolites in plants. After the formation of anthocyanidins, Flavonoid 3-O-glucosyltransferase (3GT) mediated glycosylation first occurs at the C-3 site, forming a stable anthocyanin 3-O-glucoside. Several studies have investigated the function of 3GT using biochemical methods. However, it is necessary to provide further genetic evidence for the role of Ph3GT in petunia (Petunia hybrida). In addition, there is no information regarding the subcellular localization of Ph3GT and the regulation of transcription factors on Ph3GT. In this study, the full-length Ph3GT gene from petunia (Petunia hybrida) was isolated. We found that Ph3GT is localized in the cytoplasm. Ph3GT exhibited high expression levels in the corollas during the coloring period of petunia flowers. VIGS-mediated Ph3GT silencing resulted in a lighter corolla color and a significant decrease in the anthocyanin content in six petunia cultivars. The silencing of Ph3GT affected the expression levels of eight key genes in the anthocyanin synthesis pathway. Additionally, dual luciferase and yeast one-hybrid assays showed that R2R3-MYB transcription factor PhAN2 directly regulates the transcript of Ph3GT.

Transcription factor NtMYB59 targets NtMYB12 to negatively regulate the biosynthesis of polyphenols in Nicotiana tabacum

MYB12 is a key regulator that has been shown to promote the accumulation of various phenylpropanoid compounds in plants. However, the regulation of MYB12 gene is largely unknown. In this study, we found that overexpression of the NtMYB59 gene significantly inhibited the accumulation of chlorogenic acid (CGA), flavonols, and anthocyanins in tobacco, while knock-down and knock-out of NtMYB59 significantly increased the contents of these polyphenol compounds. Transcriptome analysis between WT and NtMYB59-OE plants revealed several differentially expressed genes (DEGs) encoding crucial enzymes in the phenylpropanoid pathway and the transcription factor NtMYB12. ChIP-seq assay further indicated that NtMYB12 might be a direct target of NtMYB59. Subsequent yeast one-hybrid, electrophoretic mobility shift assay, and Dual-Luciferase assays confirmed that NtMYB59 directly binds to the promoter of NtMYB12 to inhibit its expression. Moreover, loss-function of NtMYB59 significantly promoted the accumulation of flavonols and anthocyanins in ntmyb59, but their contents in ntmyb59/ntmyb12 double mutants were significantly lower than that of WT and ntmyb59 plants, indicating that the regulation of NtMYB59 on flavonoids biosynthesis depends on the activity of NtMYB12. Our study revealed that NtMYB59 regulates the expression of NtMYB12, and provided new potential strategies for modulating phenylpropanoids biosynthesis in tobacco.

AcMYB96 promotes anthocyanin accumulation in onion (Allium cepa L) without forming the MBW complex

Anthocyanins are major flavonoid compounds with established health benefits. Although the molecular mechanisms of MYB transcription factors (TFs) within the MYB-basic helix-loop-helix (bHLH)-WD-repeat protein (MBW) complex in anthocyanin biosynthesis have been revealed, the functions of other MYB TFs that are unable to form the MBW complex in this process remain unclear. In this study, we uncovered and extensively characterized an R2R3-MYB TF in onion (Allium cepa L.), named AcMYB96, which was identified as a potential anthocyanin activator. AcMYB96 was classified into subgroup 1 of the R2R3-MYB TF family and lacked the conserved sequences required for interactions with bHLH IIIf TFs. Consistently, yeast two-hybrid assays showed that AcMYB96 did not interact with any bHLH IIIf TFs examined, including AcB2 and AtTT8. The transcription pattern of AcMYB96 correlated with the level of anthocyanin accumulation, and its role in activating anthocyanin biosynthesis was confirmed through overexpression in the epithelial cells of onion bulbs and Arabidopsis. Yeast one-hybrid, electrophoretic mobility shift, and promoter transactivation assays further demonstrated that AcMYB96 promoted anthocyanin biosynthesis by binding to the promoters of the chalcone synthase (AcCHS1), anthocyanidin synthase (AcANS), and UDP-glucose-flavonoid 3-O-glucosyltransferase (AcUFGT) genes, thereby activating their expression independent of bHLH IIIf TFs. These results demonstrate that AcMYB96 activates anthocyanin biosynthesis without forming the MBW complex, providing a theoretical foundation to further enrich the gene resources for promoting anthocyanin accumulation and breeding red onions with high anthocyanin content.

Characterization of key genes in anthocyanin and flavonoid biosynthesis during floral development in Rosa canina L

This study investigates the transition of Rosa canina L. petals from pink to white, driven by genetic and biochemical factors. It characterizes the expression of ten key genes involved in anthocyanin and flavonoid biosynthesis across five developmental stages, correlating gene expression with flavonoid and anthocyanin concentrations and colorimetric changes. Initially, the petals exhibit a rich flavonoid profile, dominated by Rutin and Kaempferol derivatives. The peak anthocyanin concentration, corresponding to the deepest color saturation, occurs in the subsequent stage. Advanced chromatographic analyses identify key flavonoids persisting into the final white petal stage. Notably, the ANS gene shows a dramatic 137.82-fold increase in expression at the final stage, indicating its crucial role in petal color maturation despite the absence of visible pigmentation. The study provides a comprehensive characterization of the genetic and biochemical mechanisms underlying petal pigmentation, suggesting that reduced anthocyanin synthesis and increased flavonol concentration led to white petals. It also highlights the roles of other genes such as PAL, CCD1, FLS, CHI, CHS, UFGT, F3H, DFR, and RhMYB1, indicating that post-translational modifications and other regulatory mechanisms may influence anthocyanin stability and degradation.

Genome-wide identification of R2R3-MYB transcription factor subfamily genes involved in salt stress in rice (Oryza sativa L.)

BACKGROUND

R2R3-MYB transcription factors belong to one of the largest gene subfamilies in plants, and they are involved in diverse biological processes. However, the role of R2R3-MYB transcription factor subfamily genes in the response of rice (Oryza sativa L.) to salt stress has been rarely reported.

RESULTS

In this study, we performed a genome-wide characterization and expression identification of rice R2R3-MYB transcription factor subfamily genes. We identified a total of 117 R2R3-MYB genes in rice and characterized their gene structure, chromosomal location, and cis-regulatory elements. According to the phylogenetic relationships and amino acid sequence homologies, the R2R3-MYB genes were divided into four groups. qRT-PCR of the R2R3-MYB genes showed that the expression levels of 10 genes significantly increased after 3 days of 0.8% NaCl treatment. We selected a high expression gene OsMYB2-115 for further analysis. OsMYB2-115 was highly expressed in the roots, stem, leaf, and leaf sheath. OsMYB2-115 was found to be localized in the nucleus, and the yeast hybrid assay showed that OsMYB2-115 has transcriptional activation activity.

CONCLUSION

This result provides important information for the functional analyses of rice R2R3-MYB transcription factor subfamily genes related to the salt stress response and reveals that OsMYB2-115 may be an important gene associated with salt tolerance in rice.

Integrated Metabolomics and Transcriptomics Reveal the Key Role of Flavonoids in the Cold Tolerance of Chrysanthemum

Chrysanthemum (Chrysanthemum morifolium, ground-cover Chrysanthemums), one of the important garden flowers, has a high ornamental and economic value. However, its ornamental value is significantly diminished by the low temperature experienced in northeastern China. Here, metabolomics and transcriptomics were performed on three Chrysanthemum cultivars before and after a low temperature to investigate the dynamic metabolite changes and the molecular regulatory mechanisms. The results showed that 1324 annotated metabolites were detected, among which 327 were identified as flavonoids derived from Chrysanthemum. The accumulation of metabolites and gene expression related to the flavonoid biosynthesis pathway significantly increased in the three cultivars under the low temperature, indicating flavonoid metabolism actively participates in the Chrysanthemum cold response. Specifically, the content of cyanidin and pelargonidin derivatives and the expression of anthocyanin biosynthesis genes significantly increases in XHBF, providing a reasonable explanation for the change in petal color from white to purple under the low temperature. Six candidate UDP-glycosyltransferase genes involved in the glycosylation of flavonoids were identified through correlation networks and phylogenetic analysis. CmNAC1, CmbZIP3, and other transcription factors potentially regulating flavonoid metabolism and responding to low temperatures were discovered by correlation analysis and weighted gene co-expression network analysis (WGCNA). In conclusion, this study elucidated the specific response of flavonoids to low temperatures in Chrysanthemums, providing valuable insights and metabolic data for investigating cold tolerance.

Improving the Traits of Perilla frutescens (L.) Britt Using Gene Editing Technology

Plant breeding has evolved significantly over time with the development of transformation and genome editing techniques. These new strategies help to improve desirable traits in plants. Perilla is a native oil crop grown in Korea. The leaves contain many secondary metabolites related to whitening, aging, antioxidants, and immunity, including rosmarinic acid, vitamin E, luteolin, anthocyanins, and beta-carotene. They are used as healthy and functional food ingredients. It is an industrially valuable cosmetics crop. In addition, perilla seeds are rich in polyunsaturated fatty acids, such as α-linolenic acid and linoleic acid. They are known to be effective in improving neutral lipids in the blood, improving blood circulation, and preventing dementia and cardiovascular diseases, making them excellent crops whose value can be increased through improved traits. This research will also benefit perilla seeds, which can increase their stock through various methods, such as the increased production of functional substances and improved productivity. Recently, significant attention has been paid to trait improvement research involving gene-editing technology. Among these strategies, CRISPR/Cas9 is highly adaptable, enabling accurate and efficient genome editing, targeted mutagenesis, gene knockouts, and the regulation of gene transcription. CRISPR/Cas9-based genome editing has enormous potential for improving perilla; however, the regulation of genome editing is still at an early stage. Therefore, this review summarizes the enhancement of perilla traits using genome editing technology and outlines future directions.

VvWRKY5 positively regulates wounding-induced anthocyanin accumulation in grape by interplaying with VvMYBA1 and promoting jasmonic acid biosynthesis

Wounding stress induces the biosynthesis of various secondary metabolites in plants, including anthocyanin. However, the underlying molecular mechanism remains elusive. Here, we reported that a transcription factor, VvWRKY5, promotes wounding-induced anthocyanin accumulation in grape (Vitis vinifera). Biochemical and molecular analyses demonstrated that wounding stress significantly increased anthocyanin content, and VvMYBA1 plays an essential role in this process. VvWRKY5 could interact with VvMYBA1 and amplify the activation effect of VvMYBA1 on its target gene VvUFGT. The transcript level of VvWRKY5 was notably induced by wounding treatment. Moreover, our data demonstrated that VvWRKY5 could promote the synthesis of jasmonic acid (JA), a phytohormone that acts as a positive modulator in anthocyanin accumulation, by directly binding to the W-box element in the promoter of the JA biosynthesis-related gene VvLOX and enhancing its activities, and this activation was greatly enhanced by the VvWRKY5-VvMYBA1 protein complex. Collectively, our findings show that VvWRKY5 plays crucial roles in wounding-induced anthocyanin synthesis in grape and elucidates the transcriptional regulatory mechanism of wounding-induced anthocyanin accumulation.

Anthocyanin gene enrichment in the distal region of cotton chromosome A07: mechanisms of reproductive organ coloration

Introduction

The biosynthesis of secondary metabolites like anthocyanins is often governed by metabolic gene clusters (MGCs) in the plant ancestral genome. However, the existence of gene clusters specifically regulating anthocyanin accumulation in certain organs is not well understood.

Methods and results

In this study, we identify MGCs linked to the coloration of cotton reproductive organs, such as petals, spots, and fibers. Through genetic analysis and map-based cloning, we pinpointed key genes on chromosome A07, such as PCC/GhTT19, which is involved in anthocyanin transport, and GbBM and GhTT2-3A, which are associated with the regulation of anthocyanin and proanthocyanidin biosynthesis. Our results demonstrate the coordinated control of anthocyanin and proanthocyanidin pathways, highlighting the evolutionary significance of MGCs in plant adaptation. The conservation of these clusters in cotton chromosome A07 across species underscores their importance in reproductive development and color variation. Our study sheds light on the complex biosynthesis and transport mechanisms for plant pigments, emphasizing the role of transcription factors and transport proteins in pigment accumulation.

Discussion

This research offers insights into the genetic basis of color variation in cotton reproductive organs and the potential of MGCs to enhance our comprehension of plant secondary metabolism.

Integrative Metabolomic and Transcriptomic Analyses Reveal the Mechanism of Petal Blotch Formation in Rosa persica

Petal blotch is a specific flower color pattern commonly found in angiosperm families. In particular, Rosa persica is characterized by dark red blotches at the base of yellow petals. Modern rose cultivars with blotches inherited the blotch trait from R. persica. Therefore, understanding the mechanism for blotch formation is crucial for breeding rose cultivars with various color patterns. In this study, the metabolites and genes responsible for the blotch formation in R. persica were identified for the first time through metabolomic and transcriptomic analyses using LC-MS/MS and RNA-seq. A total of 157 flavonoids were identified, with 7 anthocyanins as the major flavonoids, namely, cyanidin 3-O-(6″-O-malonyl) glucoside 5-O-glucoside, cyanidin-3-O-glucoside, cyanidin 3-O-galactoside, cyanidin O-rutinoside-O-malonylglucoside, pelargonidin 3-O-glucoside, pelargonidin 3,5-O-diglucoside, and peonidin O-rutinoside-O-malonylglucoside, contributing to pigmentation and color darkening in the blotch parts of R. persica, whereas carotenoids predominantly influenced the color formation of non-blotch parts. Zeaxanthin and antheraxanthin mainly contributed to the yellow color formation of petals at the semi-open and full bloom stages. The expression levels of two 4-coumarate: CoA ligase genes (Rbe014123 and Rbe028518), the dihydroflavonol 4-reductase gene (Rbe013916), the anthocyanidin synthase gene (Rbe016466), and UDP-flavonoid glucosyltransferase gene (Rbe026328) indicated that they might be the key structural genes affecting the formation and color of petal blotch. Correlation analysis combined with weighted gene co-expression network analysis (WGCNA) further characterized 10 transcription factors (TFs). These TFs might participate in the regulation of anthocyanin accumulation in the blotch parts of petals by modulating one or more structural genes. Our results elucidate the compounds and molecular mechanisms underlying petal blotch formation in R. persica and provide valuable candidate genes for the future genetic improvement of rose cultivars with novel flower color patterns.

Metabolome and Transcriptome Reveal Chlorophyll, Carotenoid, and Anthocyanin Jointly Regulate the Color Formation of Triadica sebifera

The Chinese tallow tree (Triadica sebifera) is an economically important plant on account of its ornamental value and oil-producing seeds. Leaf colour is a key characteristic of T. sebifera, with yellow-, red- and purple-leaved varieties providing visually impressive displays during autumn. In this study, we performed metabolomic and transcriptomic analyses to gain a better understanding of the mechanisms underlying leaf colour development in purple-leaved T. sebifera at three stages during the autumnal colour transition, namely, green, hemi-purple, and purple leaves. We accordingly detected 370 flavonoid metabolites and 10 anthocyanins, among the latter of which, cyanidin-3-xyloside and peonidin-3-O-glucoside were identified as the predominant compounds in hemi-purple and purple leaves. Transcriptomic analysis revealed that structural genes associated with the anthocyanin biosynthetic pathway, chlorophyll synthesis pathway and carotenoid synthesis pathway were significantly differential expressed at the three assessed colour stages. Additionally, transcription factors associated with the MYB-bHLH-WD40 complex, including 22 R2R3-MYBs, 79 bHLHs and 44 WD40 genes, were identified as candidate regulators of the anthocyanin biosynthetic pathway. Moreover, on the basis of the identified differentially accumulated anthocyanins and key genes, we generated genetic and metabolic regulatory networks for anthocyanin biosynthesis in T. sebifera. These findings provide comprehensive information on the leaf transcriptome and three pigments of T. sebifera, thereby shedding new light on the mechanisms underlying the autumnal colouring of the leaves of this tree.

Identification and Validation of Reference Genes for qRT-PCR Analysis of Petal-Color-Related Genes in Rosa praelucens

The flower's color is regarded as one of the most outstanding features of the rose. Rosa praelucens Byhouwer, an endemic and critically endangered decaploid wild rose species, is abundant in phenotypic diversity, especially in flower color variation, from white to different degrees of pink. The mechanism underlying this variation, e.g., the level of petal-color-related genes, is worth probing. Seven candidate reference genes for qRT-PCR analysis, including tubulin α chain (TUBA), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), histone H2B (Histone2A), eukaryotic translation elongation factor 1-α (EEF1A), 60S ribosomal protein (RPL37), eukaryotic translation initiation factor 1-α (EIF1A), and aquaporins (AQP), were detected from the transcriptome datasets of full blooming flowers of white-petaled and pink-petaled individuals, and their expression stabilities were evaluated through qRT-PCR analysis. According to stability rankings analysis, EEF1A showed the highest stability and could be chosen as the most suitable reference gene. Moreover, the reliability of EEF1A was demonstrated via qRT-PCR analysis of six petal-color-related target genes, the expression patterns of which, through EEF1A normalization, were found to be consistent with the findings of transcriptome analysis. The result provides an optimal reference gene for exploring the expression level of petal-color-related genes in R. praelucens, which will accelerate the dissection of petal-color-variation mechanisms in R. praelucens.

Cloned genes and genetic regulation of anthocyanin biosynthesis in maize, a comparative review

Anthocyanins are plant-based pigments that are primarily present in berries, grapes, purple yam, purple corn and black rice. The research on fruit corn with a high anthocyanin content is not sufficiently extensive. Considering its crucial role in nutrition and health it is vital to conduct further studies on how anthocyanin accumulates in fruit corn and to explore its potential for edible and medicinal purposes. Anthocyanin biosynthesis plays an important role in maize stems (corn). Several beneficial compounds, particularly cyanidin-3-O-glucoside, perlagonidin-3-O-glucoside, peonidin 3-O-glucoside, and their malonylated derivatives have been identified. C1, C2, Pl1, Pl2, Sh2, ZmCOP1 and ZmHY5 harbored functional alleles that played a role in the biosynthesis of anthocyanins in maize. The Sh2 gene in maize regulates sugar-to-starch conversion, thereby influencing kernel quality and nutritional content. ZmCOP1 and ZmHY5 are key regulatory genes in maize that control light responses and photomorphogenesis. This review concludes the molecular identification of all the genes encoding structural enzymes of the anthocyanin pathway in maize by describing the cloning and characterization of these genes. Our study presents important new understandings of the molecular processes behind the manufacture of anthocyanins in maize, which will contribute to the development of genetically modified variants of the crop with increased color and possible health advantages.

Genome-Wide Identification and Characterization of MYB Gene Family and Analysis of Its Sex-Biased Expression Pattern in Spinacia oleracea L

The members of the myeloblastosis (MYB) family of transcription factors (TFs) participate in a variety of biological regulatory processes in plants, such as circadian rhythm, metabolism, and flower development. However, the characterization of MYB genes across the genomes of spinach Spinacia oleracea L. has not been reported. Here, we identified 140 MYB genes in spinach and described their characteristics using bioinformatics approaches. Among the MYB genes, 54 were 1R-MYB, 80 were 2R-MYB, 5 were 3R-MYB, and 1 was 4R-MYB. Almost all MYB genes were located in the 0-30 Mb region of autosomes; however, the 20 MYB genes were enriched at both ends of the sex chromosome (chromosome 4). Based on phylogeny, conserved motifs, and the structure of genes, 2R-MYB exhibited higher conservation relative to 1R-MYB genes. Tandem duplication and collinearity of spinach MYB genes drive their evolution, enabling the functional diversification of spinach genes. Subcellular localization prediction indicated that spinach MYB genes were mainly located in the nucleus. Cis-acting element analysis confirmed that MYB genes were involved in various processes of spinach growth and development, such as circadian rhythm, cell differentiation, and reproduction through hormone synthesis. Furthermore, through the transcriptome data analysis of male and female flower organs at five different periods, ten candidate genes showed biased expression in spinach males, suggesting that these genes might be related to the development of spinach anthers. Collectively, this study provides useful information for further investigating the function of MYB TFs and novel insights into the regulation of sex determination in spinach.

Genetic Engineering and Genome Editing Advances to Enhance Floral Attributes in Ornamental Plants: An Update

The ornamental horticulture industry is a highly dynamic and rapidly changing market. Constant development of novel cultivars with elite traits is essential to sustain competitiveness. Conventional breeding has been used to develop cultivars, which is often laborious. Biotechnological strategies such as genetic engineering have been crucial in manipulating and improving various beneficial traits that are technically not possible through cross-breeding. One such trait is the highly desired blue-colored flower in roses and chrysanthemums, which can be achieved through transgenic technology. Advances in genome sequencing platforms have enhanced the opportunities to access the whole genome sequence in various ornamentals, facilitating the dissection of the molecular genetics and regulatory controls of different traits. The recent advent of genome editing tools, including CRISPR/Cas9, has revolutionized plant breeding. CRISPR/Cas9-based gene editing offers efficient and highly precise trait modification, contributing to various beneficial advancements. Although genome editing in ornamentals is currently in its infancy, the recent increase in the availability of ornamental genome sequences provides a platform to extend the frontiers of future genome editing in ornamentals. Hence, this review depicts the implication of various commercially valuable ornamental attributes, and details the research attempts and achievements in enhancing floral attributes using genetic engineering and genome editing in ornamental plants.

Designing of future ornamental crops: a biotechnological driven perspective

With a basis in human appreciation of beauty and aesthetic values, the new era of ornamental crops is based on implementing innovative technologies and transforming symbols into tangible assets. Recent advances in plant biotechnology have attracted considerable scientific and industrial interest, particularly in terms of modifying desired plant traits and developing future ornamental crops. By utilizing omics approaches, genomic data, genetic engineering, and gene editing tools, scientists have successively explored the underlying molecular mechanism and potential gene(s) behind trait regulation such as floral induction, plant architecture, stress resistance, plasticity, adaptation, and phytoremediation in ornamental crop species. These signs of progress lay a theoretical and practical foundation for designing and enhancing the efficiency of ornamental plants for a wide range of applications. In this review, we briefly summarized the existing literature and advances in biotechnological approaches for the improvement of vital traits in ornamental plants. The future ornamental plants, such as light-emitting plants, biotic/abiotic stress detectors, and pollution abatement, and the introduction of new ornamental varieties via domestication of wild species are also discussed.