Late Biosynthesis Genes Research Articles

Battle for control of anthocyanin biosynthesis in two Brassicaceae species infected with turnip mosaic virus.

It has previously been found that turnip mosaic virus (TuMV) greatly suppresses anthocyanin accumulation (AA) in Brassica rapa leaves, and that such leaves become infected whilst anthocyanin-enriched leaves on the same plants are rarely infected. To clarify whether AA is a defense against TuMV, in this study we examined tissue-level patterns of spontaneous AA in relation to the cellular localization of a TuMV strain that expresses a yellow fluorescent protein. We found that TuMV infection was significantly blocked by AA, suggesting that it functions as a chemical barrier against TuMV. We next analysed changes in expression of genes related to anthocyanin biosynthesis in TuMV-infected leaves of Arabidopsis. TuMV also suppressed AA that is induced by high light in Arabidopsis, and this this suppression was mainly due to inhibited expression of anthocyanin late-biosynthesis genes (LBGs). Most positive transcription factors of LBGs were also down-regulated, while the negative regulator SPL15 was highly up-regulated. Cucumber mosaic virus (CMV) also moderately suppressed AA in Arabidopsis, but in a different manner. Since it appeared that anthocyanin-enriched leaves of Arabidopsis were resistant to TuMV but not CMV, our results suggested that the anthocyanin-associated resistance that we observed was specific to TuMV.

DhMYB2 and DhbHLH1 regulates anthocyanin accumulation via activation of late biosynthesis genes in Phalaenopsis-type Dendrobium.

Phalaenopsis-type Dendrobium is a popular orchid with good ornamental and market value. Despite their popularity, molecular regulation of anthocyanin biosynthesis during flower development remains poorly understood. In this study, we systematically investigated the regulatory roles of the transcription factors DhMYB2 and DhbHLH1 in anthocyanins biosynthesis. Gene expression analyses indicated that both DhMYB2 and DhbHLH1 are specifically expressed in flowers and have similar expression patterns, showing high expression in purple floral tissues with anthocyanin accumulation. Transcriptomic analyses showed 29 differentially expressed genes corresponding to eight enzymes in anthocyanin biosynthesis pathway have similar expression patterns to DhMYB2 and DhbHLH1, with higher expression in the purple lips than the yellow petals and sepals of Dendrobium 'Suriya Gold'. Further gene expression analyses and Pearson correlation matrix analyses of Dendrobium hybrid progenies revealed expression profiles of DhMYB2 and DhbHLH1 were positively correlated with the structural genes DhF3'H1, DhF3'5'H2, DhDFR, DhANS, and DhGT4. Yeast one-hybrid and dual-luciferase reporter assays revealed DhMYB2 and DhbHLH1 can bind to promoter regions of DhF3'H1, DhF3'5'H2, DhDFR, DhANS and DhGT4, suggesting a role as transcriptional activators. These results provide new evidence of the molecular mechanisms of DhMYB2 and DhbHLH1 in anthocyanin biosynthesis in Phalaenopsis-type Dendrobium.

Tropaeolum majus R2R3 MYB Transcription Factor TmPAP2 Functions as a Positive Regulator of Anthocyanin Biosynthesis.

Anthocyanins are an important group of water-soluble and non-toxic natural pigments with antioxidant and anti-inflammatory properties that can be found in flowers, vegetables, and fruits. Anthocyanin biosynthesis is regulated by several different types of transcription factors, including the WD40-repeat protein Transparent Testa Glabra 1 (TTG1), the bHLH transcription factor Transparent Testa 8 (TT8), Glabra3 (GL3), Enhancer of GL3 (EGL3), and the R2R3 MYB transcription factor Production of Anthocyanin Pigment 1 (PAP1), PAP2, MYB113, and MYB114, which are able to form MYB-bHLH-WD40 (MBW) complexes to regulate the expression of late biosynthesis genes (LBGs) in the anthocyanin biosynthesis pathway. Nasturtium (Tropaeolum majus) is an edible flower plant that offers many health benefits, as it contains numerous medicinally important ingredients, including anthocyanins. By a comparative examination of the possible anthocyanin biosynthesis regulator genes in nasturtium varieties with different anthocyanin contents, we found that TmPAP2, an R2R3 MYB transcription factor gene, is highly expressed in “Empress of India”, a nasturtium variety with high anthocyanin content, while the expression of TmPAP2 in Arabidopsis led to the overproduction of anthocyanins. Protoplast transfection shows that TmPAP2 functions as a transcription activator; consistent with this finding, some of the biosynthesis genes in the general phenylpropanoid pathway and anthocyanin biosynthesis pathway were highly expressed in “Empress of India” and the 35S:TmPAP2 transgenic Arabidopsis plants. However, protoplast transfection indicates that TmPAP2 may not be able to form an MBW complex with TmGL3 and TmTTG1. These results suggest that TmPAP2 may function alone as a key regulator of anthocyanin biosynthesis in nasturtiums.

Comparative Transcriptome Analysis of Anthocyanin Biosynthesis in Pansy (Viola × wittrockiana Gams.)

Pansy (Viola × wittrockiana Gams.) is an important and attractive ornamental plant with a wide variety of flower colors. To date, the molecular genetic understanding of its colorful petal pigment patterns remains largely unknown. In this study, we analyzed the bicolor petals of “Mengdie” in cytological, physiological, and transcriptomic aspects. Results showed that the difference of flower colors was mainly determined by the pigment distribution in the epidermal cells. Pigment analysis indicated that anthocyanins had strong correlations with color parameters, which acted as the main factor in flower coloration. Comparative transcriptome analysis found a total of 43,908 unigenes with the mean length of 682 bp. There were 24,323, 16,668, 8507, and 7680 unigenes annotated in the Nr, Swiss-Prot, KOG, and KEGG databases, respectively. Differential expression genes (DEGs) showed that the expression of anthocyanin late biosynthesis genes (LBGs), VwF3′H, VwF3′5′H, and VwUFGT, would be likely to play a major role in the color formation of pansy. The expression patterns of selected DEGs were verified by qRT-PCR. This study contributes an excellent insight into molecular mechanism of pigment biosynthesis and provides some useful information for flower color modification in pansy.

Dynamic Changes of the Anthocyanin Biosynthesis Mechanism During the Development of Heading Chinese Cabbage (Brassica rapa L.) and Arabidopsis Under the Control of BrMYB2.

Chinese cabbage is an important vegetable mainly planted in Asian countries, and mining the molecular mechanism responsible for purple coloration in Brassica crops is fast becoming a research hotspot. In particular, the anthocyanin accumulation characteristic of purple heading Chinese cabbage, along with the plant’s growth and head developing, is still largely unknown. To elucidate the dynamic anthocyanin biosynthesis mechanism of Chinese cabbage during its development processes, here we investigated the expression profiles of 86 anthocyanin biosynthesis genes and corresponding anthocyanin accumulation characteristics of plants as they grew and their heads developed, between purple heading Chinese cabbage 11S91 and its breeding parents. Anthocyanin accumulation of 11S91 increased from the early head formation period onward, whereas the purple trait donor 95T2-5 constantly accumulated anthocyanin throughout its whole plant development. Increasing expression levels of BrMYB2 and BrTT8 together with the downregulation of BrMYBL2.1, BrMYBL2.2, and BrLBD39.1 occurred in both 11S91 and 95T2-5 plants during their growth, accompanied by the significantly continuous upregulation of a phenylpropanoid metabolic gene, BrPAL3.1; a series of early biosynthesis genes, such as BrCHSs, BrCHIs, BrF3Hs, and BrF3’H; as well as some key late biosynthesis genes, such as BrDFR1, BrANS1, BrUF3GT2, BrUF5GT, Br5MAT, and Brp-Cout; in addition to the transport genes BrGST1 and BrGST2. Dynamic expression profiles of these upregulated genes correlated well with the total anthocyanin contents during the processes of plant growth and leaf head development, and results supported by similar evidence for structural genes were also found in the BrMYB2 transgenic Arabidopsis. After intersubspecific hybridization breeding, the purple interior heading leaves of 11S91 inherited the partial purple phenotypes from 95T2-5 while the phenotypes of seedlings and heads were mainly acquired from white 94S17; comparatively in expression patterns of investigated anthocyanin biosynthesis genes, cotyledons of 11S91 might inherit the majority of genetic information from the white type parent, whereas the growth seedlings and developing heading tissues of 11S91 featured expression patterns of these genes more similar to 95T2-5. This comprehensive set of results provides new evidence for a better understanding of the anthocyanin biosynthesis mechanism and future breeding of new purple Brassica vegetables.

Three Paralogous R2R3-MYB Genes Contribute to Delphinidin-Related Anthocyanins Synthesis in Petunia hybrida

Three ANTHOCYANIN SYNTHESIS REGULATOR genes (ASR1–3) that encode R2R3-MYB transcription factors were identified recently from Petunia hybrida. In this study, we conducted additional experiments to characterize their specific function in the regulation of anthocyanin synthesis. The ASR1–3 proteins were localized in the nucleus. Analysis of their regulatory function by transient expression in the petunia corolla and yeast two-hybrid assays showed that the residues Arg at position 51 and Ala at position 102 in the N-terminal domain were essential for the regulatory function of the proteins, and the conserved domain at the C-terminal end was important for activation of the protein. RNA sequencing of overexpression (OE) and RNA-interference transgenic lines confirmed that the ASR proteins specifically induce structural genes of anthocyanin synthesis, including the early biosynthesis genes CHSj, F3H, and F3′5′H-1, the late biosynthesis genes DFR, ANS, RT, MT, AT, and GT, and the anthocyanin-related glutathione S-transferase gene AN9. In addition, a member of the detoxifying efflux carrier family, a DTX35-like gene, was upregulated by ASRs. Determination of anthocyanin/anthocyanidin contents in ASR1-OE petunia lines revealed that ASR1 especially induced the flavonoid 3′,5′-hydroxylase, which was consistent with the abundance of dihydromyricetins and delphinidins, but not cyanidins. The ASR genes were induced under high-intensity light and upregulated the expression of MYBx and MYB27, thereby providing feedback repression of anthocyanin synthesis. An updated model is presented outlining the mechanisms underlying anthocyanin synthesis in petunia.

Expression of the subgroup IIIf bHLH transcription factor CpbHLH1 from Chimonanthus praecox (L.) in transgenic model plants inhibits anthocyanin accumulation.

Overexpression of CpbHLH1 in Arabidopsis and tobacco resulted in a dramatic decrease in anthocyanin accumulation by repressing the expression of late biosynthesis genes in the flavonoid biosynthesis pathway. Many basic helix-loop-helix (bHLH) transcription factors (TFs) of subgroup IIIf have been characterized as anthocyanin-associated activators in higher plants, but information regarding bHLH TFs that inhibit anthocyanin accumulation remains scarce. In this study, the subgroup IIIf bHLH TF CpbHLH1 from Chimonanthus praecox (L.) was identified as a negative regulator of anthocyanin accumulation. Our results showed that overexpression of CpbHLH1 in model plant species, Arabidopsis and tobacco, resulted in a dramatic decrease in anthocyanin content, whereas the content of proanthocyanidin was little affected. Quantitative RT-PCR (qRT-PCR) assays of the structural genes in the flavonoid biosynthesis pathway revealed that CpbHLH1 inhibits anthocyanin accumulation mainly through repressing the expression of late biosynthesis genes (LBGs). Interactions between CpbHLH1 protein and AtPAP1/NtAN2 protein were detected via yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays. This is the first bHLH repressor of anthocyanin biosynthesis identified in dicotyledons. These results can help us better understand the anthocyanin regulatory network in plants and may provide insights into the diverse functions of bHLH proteins.

Red Chinese Cabbage Transcriptome Analysis Reveals Structural Genes and Multiple Transcription Factors Regulating Reddish Purple Color.

Reddish purple Chinese cabbage (RPCC) is a popular variety of Brassica rapa (AA = 20). It is rich in anthocyanins, which have many health benefits. We detected novel anthocyanins including cyanidin 3-(feruloyl) diglucoside-5-(malonoyl) glucoside and pelargonidin 3-(caffeoyl) diglucoside-5-(malonoyl) glucoside in RPCC. Analyses of transcriptome data revealed 32,395 genes including 3345 differentially expressed genes (DEGs) between 3-week-old RPCC and green Chinese cabbage (GCC). The DEGs included 218 transcription factor (TF) genes and some functionally uncharacterized genes. Sixty DEGs identified from the transcriptome data were analyzed in 3-, 6- and 9-week old seedlings by RT-qPCR, and 35 of them had higher transcript levels in RPCC than in GCC. We detected cis-regulatory motifs of MYB, bHLH, WRKY, bZIP and AP2/ERF TFs in anthocyanin biosynthetic gene promoters. A network analysis revealed that MYB75, MYB90, and MYBL2 strongly interact with anthocyanin biosynthetic genes. Our results show that the late biosynthesis genes BrDFR, BrLDOX, BrUF3GT, BrUGT75c1-1, Br5MAT, BrAT-1, BrAT-2, BrTT19-1, and BrTT19-2 and the regulatory MYB genes BrMYB90, BrMYB75, and BrMYBL2-1 are highly expressed in RPCC, indicative of their important roles in anthocyanin biosynthesis, modification, and accumulation. Finally, we propose a model anthocyanin biosynthesis pathway that includes the unique anthocyanin pigments and genes specific to RPCC.

Low Temperature Promotes Anthocyanin Biosynthesis and Related Gene Expression in the Seedlings of Purple Head Chinese Cabbage (Brassica rapa L.).

To elucidate the effect of low temperature on anthocyanin biosynthesis in purple head Chinese cabbage, we analyzed anthocyanin accumulation and related gene expression in the seedlings of purple head Chinese cabbage, white head parent Chinese cabbage, and its purple male parent under a normal 25 °C temperature and a low 12 °C temperature. Anthocyanin accumulation in purple lines was strongly induced by low temperature, and the total anthocyanin content of seedlings was significantly enhanced. In addition, nearly all phenylpropanoid metabolic pathway genes (PMPGs) were down-regulated, some early biosynthesis genes (EBGs) were up-regulated, and nearly all late biosynthesis genes (LBGs) directly involved in anthocyanin biosynthesis showed higher expression levels in purple lines after low-temperature induction. Interestingly, a R2R3-MYB transcription factor (TF) gene ‘BrMYB2’ and a basic-helix-loop-helix (bHLH) regulatory gene ‘BrTT8’ were highly up-regulated in purple lines after low temperature induction, and two negative regulatory genes ‘BrMYBL2.1’ and ‘BrLBD38.2’ were up-regulated in the white line. BrMYB2 and BrTT8 may play important roles in co-activating the anthocyanin structural genes in purple head Chinese cabbage after low-temperature induction, whereas down-regulation of BrMYB2 and up-regulation of some negative regulators might be responsible for white head phenotype formation. Data presented here provide new understanding into the anthocyanin biosynthesis mechanism during low temperature exposure in Brassica crops.

A Transcriptional Network Makes Normal Tomato Fruit Not Purple

A Transcriptional Network Makes Normal Tomato Fruit Not Purple

GLABRA2, A Common Regulator for Epidermal Cell Fate Determination and Anthocyanin Biosynthesis in Arabidopsis.

Epidermal cell fate determination—including trichome initiation, root hair formation, and flavonoid and mucilage biosynthesis in Arabidopsis (Arabidopsis thaliana)—are controlled by a similar transcriptional regulatory network. In the network, it has been proposed that the MYB-bHLH-WD40 (MBW) activator complexes formed by an R2R3 MYB transcription factor, a bHLH transcription factor and the WD40-repeat protein TRANSPARENT TESTA GLABRA1 (TTG1) regulate the expression of downstream genes required for cell fate determination, flavonoid or mucilage biosynthesis, respectively. In epidermal cell fate determination and mucilage biosynthesis, the MBW activator complexes activate the expression of GLABRA2 (GL2). GL2 is a homeodomain transcription factor that promotes trichome initiation in shoots, mucilage biosynthesis in seeds, and inhibits root hair formation in roots. The MBW activator complexes also activate several R3 MYB genes. The R3 MYB proteins, in turn, competing with the R2R3 MYBs for binding bHLH transcription factors, therefore inhibiting the formation of the MBW activator complexes, lead to the inhibition of trichome initiation in shoots, and promotion of root hair formation in roots. In flavonoid biosynthesis, the MBW activator complexes activate the expression of the late biosynthesis genes in the flavonoid pathway, resulting in the production of anthocyanins or proanthocyanidins. Research progress in recent years suggests that the transcriptional regulatory network that controls epidermal cell fate determination and anthocyanin biosynthesis in Arabidopsis is far more complicated than previously thought. In particular, more regulators of GL2 have been identified, and GL2 has been shown to be involved in the regulation of anthocyanin biosynthesis. This review focuses on the research progress on the regulation of GL2 expression, and the roles of GL2 in the regulation of epidermal cell fate determination and anthocyanin biosynthesis in Arabidopsis.

Differential expression of anthocyanin biosynthesis genes in Daucus carota callus culture in response to ammonium and potassium nitrate ratio in the culture medium.

Anthocyanins are major water-soluble and dynamic colouring plant pigment present in plant tissues with the high antioxidant properties. The role of ammonium and potassium nitrate in the culture medium on anthocyanin augmentation is probed thoroughly, but the mechanism of its biosynthesis continues to be unclear. Hence, the present study was undertaken to optimise nitrate ratio in the culture medium for anthocyanin augmentation and examination of its biosynthesis pathway in callus culture of Daucus carota. MS basal medium fortified with various ratio of NH4NO3:KNO3 was employed to find their impact on biomass, anthocyanin augmentation and the expression profile of anthocyanin biosynthesis genes in the callus culture. The data indicated that the highest anthocyanin content (9.30 ± 0.25mg/100g FW) was seen in callus grown on the medium supplemented with 20.0mM NH4NO3:37.6mM KNO3 and the least was seen in the medium which contained 40.0mM NH4NO3:18.8mM KNO3 (2.74 ± 0.27mg/100g FW). This indicates an optimal concentration of NH4NO3:KNO3 ratio is essential to produce a higher amount of anthocyanin in in vitro culture. Meanwhile, anthocyanin biosynthesis genes were differentially expressed as confirmed by qRT-PCR in the time interval of 5, 10, 15, 20 and 25days. The transcript levels of nine anthocyanin biosynthesis genes were increased in the response of varying NH4NO3:KNO3 ratio in the medium. The transcript level of early genes PAL, 4CL, CHS and CHI increased by 19.5, 21.0, 16.2 and 9.98-fold, respectively, compared with control. In addition, late biosynthesis genes LDOX and UFGT resulted in the transcript level of 11.3 and 13.6-fold, respectively.

An R2R3-MYB Transcription Factor FtMYB15 Involved in the Synthesis of Anthocyanin and Proanthocyanidins from Tartary Buckwheat

Tartary buckwheat is an excellent medicinal and nutrient-rich crop that contains abundant flavonoids. Flavonoids, such as anthocyanin and proanthocyanidin, can be accumulated in plants for resistance to abiotic stresses, for instance, UV-B and cold. In this study, an R2R3-MYB transcription factor gene named FtMYB15 was isolated from tartary buckwheat. A phylogenetic tree suggested that FtMYB15 potentially plays a role in flavonoid biosynthesis. Consequently, the ectopic overexpression of FtMYB15 was conducted in Arabidopsis. Transgenic lines exerted increased pigmentation in leaves and seed coats, as well as higher accumulation levels of anthocyanin and proanthocyanidin in Arabidopsis. Specifically, anthocyanin and proanthocyanidin in transgenic lines were 8.62- and 4.93 (P < 0.01)-fold higher than wild-type Arabidopsis, respectively. Meanwhile, the expressions of both early and late biosynthesis genes, including AtCHS, AtCHI, AtF3H, AtF3′H, AtDFR, AtANS, AtBAN, and AtTT12, in the anthocyanin and proanthocyanidin pathway were enhanced (P < 0.01). Particularly, AtDFR and AtANS were upregulated 4.13 and 5.11 (P < 0.01) times higher than the control, respectively, whereas AtBAN and AtTT12 were upregulated a 100-fold (P < 0.01) compared to wild-type Arabidopsis. Only AtFLS expression decreased in transgenic Arabidopsis (P < 0.01). These results laid a foundation for better understanding of flavonoid biosynthesis and its molecular regulation mechanism in tartary buckwheat.

Molecular cloning and characterization of anthocyanin biosynthesis genes in eggplant (Solanum melongena L.)

Eggplant is rich in anthocyanins, which are one of the important secondary metabolites and beneficial to human health. In this study, four anthocyanin biosynthesis genes, including chalcone synthase (SmCHS), chalcone isomerase (SmCHI), flavanone 3-hydroxylase (SmF3H) and dihydroflavonol 4-reductase (SmDFR), were isolated from eggplant. Their expression profiles were investigated along with other two structural genes (SmF3′5′H and SmANS) in different tissues, bagging, and low-temperature treatments. The highest expression levels were observed in peels except for SmF3H which was detected in stems, and SmF3H was also the exclusive gene that did not show correlation with anthocyanin content. Unlike purple peels of the control, the bagged fruits displayed white peels and had no anthocyanin accumulation, because of the expression of SmCHI, SmF3′5′H, SmDFR, and SmANS totally depended on light. As low temperature stimulates anthocyanin accumulation, all the six anthocyanin biosynthesis genes were up-regulated in cold stress experiment, and SmCHS increased most obviously. Moreover, early biosynthesis genes (SmCHS, SmCHI, and SmF3H) responded earlier than late biosynthesis genes (SmF3′5′H, SmDFR, and SmANS) under low temperature. Subcellular localization suggested that the enzymes encoded by the genes cloned in this study were all located in cytosol and nucleus. To further characterize the function, their ectopic expression in Arabidopsis was performed, and overexpression lines displayed higher anthocyanin accumulation in stems and siliques. The present study provides insight into anthocyanin biosynthesis in eggplant and may facilitate genetic engineering for improvement of the anthocyanin content in plants.

Anthocyanins accumulate in tartary buckwheat (Fagopyrum tataricum) sprout in response to cold stress

Tartary buckwheat (Fagopyrum tataricum )i s rich in flavonoids. Anthocyanins, a special class of flavo- noids, offer significant nutrients and provide the red pig- ment found in sprouts. The anthocyanins biosynthesis has been shown influenced by environmental stress. In this study, we investigate the effects of cold stress on antho- cyanins biosynthesis of tartary buckwheat sprouts. On cellular level, cross-sectional observations were performed and result indicated that anthocyanins accumulated pri- marily in the epidermal and cortex cells of hypocotyls. Biochemical analysis, including anthocyanin quantifica- tion, thin-layer chromatography and radical scavenging assay, showed that cold stress significantly increased the synthesis of anthocyanins and antioxidant activity of tar- tary buckwheat sprouts. At the molecular level, semi-RT- PCR was used to investigate 14 anthocyanin-related genes in tartary buckwheat sprouts treated with cold stress. All the selected genes were upregulated in cold-stressed sprouts, except for FtGST, FtAHA, and FtMYB. More importantly, the expression level of three late biosynthesis genes, FtF3 0 H, FtDFR, and FtANS, was highest in hypo- cotyl tissue. Our results suggest that anthocyanins play a considerable role in the cold stress tolerance of tartary buckwheat sprouts.

Characterization of an activation-tagged mutant uncovers a role of GLABRA2 in anthocyanin biosynthesis in Arabidopsis.

In Arabidopsis, anthocyanin biosynthesis is controlled by a MYB-bHLH-WD40 (MBW) transcriptional activator complex. The MBW complex activates the transcription of late biosynthesis genes in the flavonoid pathway, leading to the production of anthocyanins. A similar MBW complex regulates epidermal cell fate by activating the transcription of GLABRA2 (GL2), a homeodomain transcription factor required for trichome formation in shoots and non-hair cell formation in roots. Here we provide experimental evidence to show that GL2 also plays a role in regulating anthocyanin biosynthesis in Arabidopsis. From an activation-tagged mutagenized population of Arabidopsis plants, we isolated a dominant, gain-of-function mutant with reduced anthocyanins. Molecular cloning revealed that this phenotype is caused by an elevated expression of GL2, thus the mutant was named gl2-1D. Consistent with the view that GL2 acts as a negative regulator of anthocyanin biosynthesis, gl2-1D seedlings accumulated less whereas gl2-3 seedlings accumulated more anthocyanins in response to sucrose. Gene expression analysis indicated that expression of late, but not early, biosynthesis genes in the flavonoid pathway was dramatically reduced in gl2-1D but elevated in gl2-3 mutants. Further analysis showed that expression of some MBW component genes involved in the regulation of late biosynthesis genes was reduced in gl2-1D but elevated in gl2-3 mutants, and chromatin immunoprecipitation results indicated that some MBW component genes are targets of GL2. We also showed that GL2 functions as a transcriptional repressor. Taken together, these results indicate that GL2 negatively regulates anthocyanin biosynthesis in Arabidopsis by directly repressing the expression of some MBW component genes.

Anthocyanin accumulation and expression pattern of anthocyanin biosynthesis genes in developing wheat coleoptiles

Anthocyanin accumulation and expression pattern of anthocyanin biosynthesis genes were investigated in developing coleoptiles of wheat (Triticum aestivum L.). In epidermal cell layers of the growing coleoptiles of cv. Hope, anthocyanins started to accumulate between day 2 and 3 after germination, reached their maximum on day 6 and then decreased while another cultivar, Chinese Spring (CS) did not accumulate anthocyanin pigments. None of the six anthocyanin biosynthesis genes was upregulated in coleoptiles of both cvs. grown in the dark, whereas all genes were activated by light in coleoptiles of cv. Hope. Transcript levels of all the six genes were relatively low on day 2, increased from days 3 to 5 and then declined to almost non-detectable levels on day 6. In coleoptiles of CS grown in the light, the early biosynthesis genes (EBGs) were expressed, but the three late biosynthesis genes (LBGs) were not.

The wheat Rc gene for red coleoptile colour codes for a transcriptional activator of late anthocyanin biosynthesis genes

Genes that regulate anthocyanin pigmentation in wheat coleoptiles were investigated in three lines of wheat. When grown in the light, the wheat line Hope developed red coleoptiles, while another line, Chinese Spring (CS), expressed green coleoptiles. Another line CS(Hope7A), a chromosome substitution line that carries chromosome 7A of Hope in a CS background, also developed a red coleoptile. In the dark, none of the three lines developed colored coleoptiles. Anthocyanin biosynthesis pathway genes have been grouped into two subsets: early biosynthesis genes (EBGs), which include CHS, CHI and F3H, and late biosynthesis genes (LBGs), which include DFR, ANS and UFGT. None of these six genes was upregulated in coleoptiles grown in the dark, whereas all were activated by light in coleoptiles of Hope and CS(Hope7A). In coleoptiles of CS grown in the light, the EBGs were expressed, but the three LBGs were not. The Rc gene located on chromosome 7 appears to encode a transcription activator of LBGs involved in light-regulation of anthocyanin synthesis.