Higher Anthocyanin Accumulation Research Articles

Regulation of Anthocyanin Accumulation by a Transcription Factor LcTT8 From Lonicera caerulea L.

The fruit of Lonicera caerulea L. is rich in anthocyanin, which has beneficial effects on human health. However, there is no research report on the regulation mechanism of anthocyanin synthesis in Lonicera caerulea L. TT8 gene-encoded protein belongs to bHLH transcription factor, and it has been reported to regulate anthocyanin synthesis. In the study, we cloned TT8 gene from Lonicera caerulea L. named “Berel” and transformed into tobacco (Nicotiana tabacum) to characterize its function. The open-reading frame of LcTT8 was 2049 bp, encoding a protein of 682 amino acids. The phylogenetic tree analysis showed that LcTT8 protein had the highest homology with TT8 in Paeonia suffruticosa. The analysis of expression in different tissues showed that the expression level of LcTT8 was higher in fruits than that in flowers, leaves, stems, and roots, and the expression level reached the peak at the early stage of fruit color change. The subcellular localization results showed that the LcTT8 protein was mainly localized in the nucleus. A total of ten LcTT8 overexpression transgenic tobacco were obtained. The ELISA results revealed that the anthocyanin content in the transgenic tobacco leaves was increased by 36.84% compared with the wild-type tobacco. The qPCR results showed that the overexpression of LcTT8 caused the up-expression of key genes of anthocyanin synthesis, including F3H, DFR, and ANS. Similarly, the enzyme activities of DFR and ANS were significantly increased in the transgenic lines (P < 0.05). Our research reveals the expression patterns and molecular characteristic of LcTT8 gene in anthocyanin synthesis, providing new possibilities for the breeding of blue honeysuckle and other fruit plants with high anthocyanin accumulation.

The Role of Gibberellins in Regulation of Nitrogen Uptake and Physiological Traits in Maize Responding to Nitrogen Availability.

Modified gibberellin (GA) signaling leads to semi-dwarfism with low nitrogen (N) use efficiency (NUE) in crops. An understanding of GA-mediated N uptake is essential for the development of crops with improved NUE. The function of GA in modulating N uptake capacity and nitrate (NO3−) transporters (NRTs) was analyzed in the GA synthesis-deficient mutant zmga3ox grown under low (LN) and sufficient (SN) N conditions. LN significantly suppressed the production of GA1, GA3, and GA4, and the zmga3ox plants showed more sensitivity in shoots as well as LN stress. Moreover, the higher anthocyanin accumulation and the decrease of chlorophyll content were also recorded. The net NO3− fluxes and 15N content were decreased in zmga3ox plants under both LN and SN conditions. Exogenous GA3 could restore the NO3− uptake in zmga3ox plants, but uniconazole repressed NO3− uptake. Moreover, the transcript levels of ZmNRT2.1/2.2 were downregulated in zmga3ox plants, while the GA3 application enhanced the expression level. Furthermore, the RNA-seq analyses identified several transcription factors that are involved in the GA-mediated transcriptional operation of NRTs related genes. These findings revealed that GAs influenced N uptake involved in the transcriptional regulation of NRTs and physiological responses in maize responding to nitrogen supply.

ОЦЕНКА БИОХИМИЧЕСКОГО СОСТАВА ЯГОД ЕЖЕВИКИ В СВЯЗИ С ИСПОЛЬЗОВАНИЕМ В СЕЛЕКЦИИ

The work summarized the literature data on the content of chemicals in blackberries grown in various regions of Russia and foreign countries. Much attention is paid to the level of accumulation of biochemical components: soluble solids, sugars, organic acids, vitamins C (ascorbic acid) and P (phenolic compounds). In the studied regions, a high accumulation of anthocyanins (307-651 mg / 100 g) and ascorbic acid (23.4-54.0 mg / 100 g) in blackberries was noted in the Republic of Adygea. The highest sugar content (9.9%) was in blackberries grown in the middle zone of Russia. The average content of the studied components depends not only on the region of cultivation, but, first of all, on the varietal composition of the crop. The study of 25 blackberry varieties bred in the USA, England and Australia in the Krasnodar Territory allowed us to identify the most adapted of them for cultivation in the south of Russia,the most promising varieties are Thornfree, Smoothstem and Black Satin. In the Republic of Belarus, blackberries are grown on personal subsidiary plots, the most common is the American Agavam variety, which is noted for its high sugar content and the content of P-active substances. At the Maikop Experimental Station. N.I. Vavilov, as a result of studying the biochemical composition of blackberry berries, the following varieties were identified: by the content of dry matter – Oregon, Black Satin, Thornfree; sugar content – Oregon, Silvon, Black Satin, Thornfree, Young; by the content of organic acids – Derrow, Raven (1.67%), Cherokki (1.87%); by the content of ascorbic acid – Himalaya (54.6 mg / 100 g), Derrow (45.8 mg / 100 g), Raven (45.4 mg / 100 g) and Cherokki (47.8 mg / 100 g).

Particular qualities of wine grape varieties for high-quality varietal wine-making in conditions of the Krasnodar region

Modern development of the Russian viticultural and winemaking industry is aimed at the production of competitive varietal premium wines. It is premised on acceleration of the breeding process of domestic wine grape varieties with the preset course of processing. The purpose of this workск was to study the ratio between the most important quality components of the wines made from two classical and eight promising grape varieties domestic breeding (by Federal State Budget Scientific Institution “North Caucasian Federal Scientific Centre of Horticulture, Viticulture and Winemaking”, hereafter - Institute) to determine the unique varietal particular qualities. The experiment was performed in 2013–2018. The grapes were picked from two plots located in the Central zone and in the Taman subzone, Krasnodar region. The red varietal wines were made according to the same technology and observing the same processing modes. The analytical research was performed repeatedly with qualification assessment of the results. Two-way-ANOVA was used to identify the impact factors upon the wine components. As a result, the following appreciable grape varieties of the Institute’s breeding were isolated, which demonstrated high accumulation of phenolic substances (over 3,000 mg/l) and anthocyanins (700–1100 mg/l) in wine: Vladimir, Granatovy, Kurchansky, Dmitri; the grape varieties with high accumulation of trans-resveratrol in wine: Vladimir (4.7 mg/l), Dmitri (4.7 mg/l), and Kurchansky (3.0 mg/l); the grape varieties for which wine the mass concentration of malic acid was by 2 to 2.5 times higher than the content of tartaric acid: Vladimir and Dmitri. It was shown that Antaris variety has low ecological plasticity and wine of this variety could be differ qualitatively depending upon edaphoclimatic conditions of the subzone.

Overexpression of Maize ZmC1 and ZmR Transcription Factors in Wheat Regulates Anthocyanin Biosynthesis in a Tissue-Specific Manner.

Maize ZmC1 and ZmR transcription factors belong to the MYB-type and bHLH families, respectively, and control anthocyanin biosynthesis. In this study, Agrobacterium-mediated transformation was used to generate transgenic wheat plants that overexpress ZmC1 and ZmR or both, with the objective of developing anthocyanin-enriched wheat germplasm. Three kinds of stable transgenic wheat lines were obtained. The integration of target genes in the transgenic wheat plants was confirmed by fluorescence in situ hybridization (FISH) analysis. We found that single overexpression of ZmC1 regulates pigmentation in the vegetative tissues such as coleoptiles, auricles, and stems. The single overexpression of ZmR controls the coloration in reproductive tissue like spikelets and seeds. The simultaneous overexpression of ZmC1 and ZmR showed the strongest pigmentation in almost all tissues. Furthermore, quantitative real-time PCR (qRT-PCR) analysis revealed that expression of the two transgenes, and of two conserved homologous and six associated structural genes involved in anthocyanin biosynthesis in wheat were greatly up-regulated in the transgenic plants. Similarly, quantitative analysis for anthocyanin amounts based on HPLC-MS also confirmed that the transgenic wheat plants with combined overexpression of ZmC1 and ZmR accumulated the highest quantity of pigment products. Moreover, developing seeds overexpressing ZmR exposed to light conditions showed up-regulated transcript levels of anthocyanin biosynthesis-related genes compared to dark exposure, which suggests an important role of light in regulating anthocyanin biosynthesis. This study provides a foundation for breeding wheat materials with high anthocyanin accumulation and understanding the mechanism of anthocyanin biosynthesis in wheat.

New cold-tolerant grapevine cultivars for red wines

Krasnodar Region is the main region of industrial viticulture in the Russian Federation. Natural conditions allow high-quality cultivars to be grown there; however, in certain years, the impact of low-temperature stresses of the winter period, summer droughts and diseases limit the stable high-yield production of Vitis vinifera. Breeding of grapevine cultivars for high-quality winemaking and adaptability to local agro-climatic conditions is carried out at the North-Caucasian Federal Scientific Center of Horticulture, Viticulture and Wine-making. Interspecific hybrids are used as donors of resistance in crosses with high-quality V. vinifera cultivars. New hybrids were studied by agrobiological research, and wines and must from grapes were studied by organoleptic evaluation, physico-chemical and biological indicators. Highly adaptive cultivars ‘Dmitriy’, ‘Kurchanskiy’ and ‘Vladimir’ for red wines were selected as a result. They are tolerant to low temperatures in winter, down to -27°C. The cultivars have high levels of resistance to the main pathogens (mildew, botrytis), and ‘Dmitriy’ is resistant to root phylloxera. Yields of ‘Kurchanskiy’ and ‘Vladimir’ were 12-13 t ha(‑1), and that of ‘Dmitriy’ was 14-15 t ha(‑1). These cultivars combine adaptability to the unstable conditions of the south of Russia with high-quality wine production. ‘Vladimir’ is distinguished by the total amount of phenolic substances (average 3603 mg L(‑1)). Samples of wine from ‘Kurchanskiy’ and ‘Dmitriy’ show high accumulation of anthocyanins (more than 1000 mg L(‑1)). The cultivars are now being tested by governmental authorities.

A HORT1 Retrotransposon Insertion in the PeMYB11 Promoter Causes Harlequin/Black Flowers in Phalaenopsis Orchids.

The harlequin/black flowers in Phalaenopsis orchids contain dark purple spots and various pigmentation patterns, which appeared as a new color in 1996. We analyzed this phenotype by microscopy, HPLC, gene functional characterization, genome structure analysis, and transient overexpression system to obtain a better understanding of the black color formation in Phalaenopsis orchids. Most mesophyll cells of harlequin flowers showed extremely high accumulation of anthocyanins as well as a high expression of Phalaenopsis equestris MYB11 (PeMYB11) as the major regulatory R2R3-MYB transcription factor for regulating the production of the black color. In addition, we analyzed the expression of basic helix-loop-helix factors, WD40 repeat proteins, and MYB27- and MYBx-like repressors for their association with the spot pattern formation. To understand the high expression of PeMYB11 in harlequin flowers, we isolated the promoter sequences of PeMYB11 from red and harlequin flowers. A retrotransposon, named Harlequin Orchid RetroTransposon 1 (HORT1), was identified and inserted in the upstream regulatory region of PeMYB11 The insertion resulted in strong expression of PeMYB11 and thus extremely high accumulation of anthocyanins in the harlequin flowers of the Phalaenopsis Yushan Little Pearl variety. A dual luciferase assay showed that the insertion of HORT1 enhanced PeMYB11 expression by at least 2-fold compared with plants not carrying the insertion. Furthermore, the presence of HORT1 explains the high mutation rates resulting in many variations of pigmentation patterning in harlequin flowers of Phalaenopsis orchids.

High anthocyanin accumulation in an Arabidopsis mutant defective in chloroplast biogenesis

Anthocyanin has an important antioxidant protective effect on plant resistance to oxidative stress. In this study, an Arabidopsis mutant dpg1 (delayed pale-greening) with a chloroplast development defect was studied. It was found that the anthocyanin accumulation of this mutant had increased during the seedling stage, and the expressions of the anthocyanin biosynthetic and regulatory genes were up-regulated. Further studies showed that exogenous ABA (abscisic acid) treatments significantly promoted the chloroplast development of the dpg1 mutant, and the anthocyanin content was significantly decreased to the level of the wild-type. When using NF (norflurazon) to simulate the oxidative stress treatments of wild-type Arabidopsis, the anthocyanin content had significantly increased compared with the control. However, the exogenous ABA treatments could significantly reduce the anthocyanin accumulation level induced by the oxidative stress. Furthermore, the components ABI1 (abscisic acid insensitive 1) and ABI3 (abscisic acid insensitive 3) of the ABA signaling pathway were found to play important roles during this process. These results indicate that the increases in the anthocyanin accumulation in the dpg1 mutant seedlings could be mediated by oxidative stress. Meanwhile, the ABI1 and ABI3 were involved in the process of the ABA inhibiting anthocyanin accumulation which had been induced by the oxidative stress.

Post-translational and transcriptional regulation of phenylpropanoid biosynthesis pathway by Kelch repeat F-box protein SAGL1.

A Kelch repeat F-box containing protein, SMALL AND GLOSSY LEAVES1 (SAGL1) regulates phenylpropanoid biosynthesis as a post-translational regulator for PAL1 (phenylalanine ammonia-lyase) and an indirect transcriptional regulator for ANTHOCYANIDIN SYNTHASE. Phenylpropanoid biosynthesis in plants produces diverse aromatic metabolites with important biological functions. Phenylalanine ammonia-lyase (PAL) catalyzes the first step in phenylpropanoid biosynthesis by converting L-phenylalanine to trans-cinnamic acid. Here, we report that SMALL AND GLOSSY LEAVES1 (SAGL1), a Kelch repeat F-box protein, interacts with PAL1 protein for proteasome-mediated degradation to regulate phenylpropanoid biosynthesis in Arabidopsis. Mutations in SAGL1 caused high accumulation of anthocyanins and lignin derived from the phenylpropanoid biosynthesis pathway. We found that PAL enzyme activity increased in SAGL1-defective mutants, sagl1, but decreased in SAGL1-overexpressing Arabidopsis (SAGL1OE) without changes in the transcript levels of PAL genes, suggesting protein-level regulation by SAGL1. Indeed, the levels of PAL1-GFP fusion protein were reduced when both SAGL1 and PAL1-GFP were transiently co-expressed in leaves of Nicotiana benthamiana. In addition, bimolecular fluorescence complementation analysis suggested an interaction between SAGL1 and PAL1. We also found that the transcript levels of ANTHOCYANIDIN SYNTHASE (ANS) increased in the sagl1 mutants but decreased in SAGL1OE. Our results suggest that SAGL1 regulates phenylpropanoid biosynthesis post-translationally at PAL1 and transcriptionally at ANS.

Enhanced anthocyanin accumulation confers increased growth performance in plants under low nitrate and high salt stress conditions owing to active modulation of nitrate metabolism

Plants require nitrogen (N) for growth and development. However, they are frequently exposed to conditions of nitrogen deficiency. In addition, anthocyanin accumulation is induced under salt stress and nitrate deficiency. To date, most studies have revealed that nitrate deficiency under high sucrose levels induce high levels of anthocyanin accumulation in plants. However, the underlying mechanisms remain unclear. Under nitrate-starved conditions, plant growth rapidly worsens and cells eventually die. In addition, plants are severely affected by salt exposure. Therefore, in this study, we determined whether increased levels of anthocyanin could improve plant growth under salt stress and nitrate-starved conditions. We used PAP1-D/fls1ko and ttg1 plants which have a perturbed anthocyanin biosynthesis pathway to explore the role of anthocyanin in plant adaptation to nitrate-deficient conditions and salt stress. Our results demonstrate that high anthocyanin accumulation in PAP1-D/fls1ko plants confers enhanced tolerance to nitrate-deficient conditions combined with high salinity. PAP1-D/fls1ko plants appeared to use absorbed nitrate efficiently during the nitrate reduction process. In addition, nitrate-related genes such as NRT1.1, NiA1 and NiA2 were upregulated in the PAP1-D/fls1ko plants. On the basis of these findings, it can be concluded that high anthocyanin accumulation helps plants to cope with salt stress under nitrate-deficient conditions via the effective utilization of nitrate metabolism.

Changes in Anthocyanin and Fruit Quality Attributes of Barberry (Berberis vulgaris L.) Grown in Different Altitude During Growth and Maturation

Purpose: Seedless barberry is one of the economical sources of anthocyanin pigment. However, short harvesting period creates many difficulties in harvesting and drying processes, leading to low quality. Therefore, it was very important to study different barberry growing areas and also evaluating fruit quality in these regions, to propose sooner harvesting in some regions.Research Method: The study was conducted in two regions (Marack and Amirabad) of Birjand suburbs, South Khorasan, Iran, during two growing seasons (2014-2015), to investigate the major physicochemical changes of barberry fruit during different growth and development stages (89, 121, 152, 183 and 214 days after full bloom (DAFB)).Findings: The results showed that fruit fresh weight and volume, pH, total soluble solids (TSS), maturity index and anthocyanin significantly increased, as harvest season progressed. The region conditions also influenced the above-mentioned parameters. Data indicated that lower night temperatures in the Marack led to better fruit indices compared with Amirabad, which may be resulted from a higher altitude as compared to Amirabad. The better fruit maturity index and anthocyanin content obtained in Marack at the fourth harvest date (183 DAFB), compared with Amirabad, which creates a sooner harvest potential. With regard to data obtained and especially higher anthocyanin accumulation, we propose mountainous regions for seedless barberry cultivation, compared to lands as it leads to sooner harvesting and better quality of fruit for fresh market.Research Limitations: It was better to study the physicochemical changes of barberry fruits in more important regions and with different altitude.Originality/Value: This study provides an insight into mountains with high altitude as main regions for barberry cultivation to increase the nutritional quality of fruit.

Abscisic Acid Regulates Anthocyanin Biosynthesis and Gene Expression Associated With Cell Wall Modification in Ripening Bilberry (Vaccinium myrtillus L.) Fruits.

Ripening of non-climacteric bilberry (Vaccinium myrtillus L.) fruit is characterized by a high accumulation of health-beneficial anthocyanins. Plant hormone abscisic acid (ABA) and sucrose have been shown to be among the central signaling molecules coordinating non-climacteric fruit ripening and anthocyanin accumulation in some fruits such as strawberry. Our earlier studies have demonstrated an elevation in endogenous ABA level in bilberry fruit at the onset of ripening indicating a role for ABA in the regulation of bilberry fruit ripening. In the present study, we show that the treatment of unripe green bilberry fruits with exogenous ABA significantly promotes anthocyanin biosynthesis and accumulation both in fruits attached and detached to the plant. In addition, ABA biosynthesis inhibitor, fluridone, delayed anthocyanin accumulation in bilberries. Exogenous ABA also induced the expression of several genes involved in cell wall modification in ripening bilberry fruits. Furthermore, silencing of VmNCED1, the key gene in ABA biosynthesis, was accompanied by the down-regulation in the expression of key anthocyanin biosynthetic genes. In contrast, the treatment of unripe green bilberry fruits with exogenous sucrose or glucose did not lead to an enhancement in the anthocyanin accumulation neither in fruits attached to plant nor in post-harvest fruits. Moreover, sugars failed to induce the expression of genes associated in anthocyanin biosynthesis or ABA biosynthesis while could elevate expression of some genes associated with cell wall modification in post-harvest bilberry fruits. Our results demonstrate that ABA plays a major role in the regulation of ripening-related processes such as anthocyanin biosynthesis and cell wall modification in bilberry fruit, whereas sugars seem to have minor regulatory roles in the processes. The results indicate that the regulation of bilberry fruit ripening differs from strawberry that is currently considered as a model of non-climacteric fruit ripening. In this study, we also identified transcription factors, which expression was enhanced by ABA, as potential regulators of ABA-mediated bilberry fruit ripening processes.

Characterization of novel mutants of hexaploid wheat (Triticum aestivum L.) with various depths of purple grain color and antioxidant capacity.

Wheat grain is recognized as a rich source of nutrients, including proteins, vitamins, minerals, fibers and antioxidants. In recent years, the focus of wheat breeding has been to increase the content of bioactive compounds to improve human health and prevent diseases. Five novel wheat mutant lines with variable seed color were developed using gamma irradiation of hexaploid wheat inbred line K4191 (purple seed color). The total anthocyanin contents of three mutant lines (L47, L167 and L925) were significantly higher than those of wild-type lines, including K4191 and 'Keumkang' (white seed color). L925 showed the highest total anthocyanin content, and cyanidin-3-glucoside was presented as the most predominant anthocyanin. Compared with 'Keumkang', the expression of anthocyanin biosynthesis genes was significantly up-regulated in purple seed mutant lines. The highest antioxidant activity was observed in L925 extracts. The expression of a few antioxidant-related genes and total anthocyanin content were positively correlated with antioxidant capacity. These data suggest that anthocyanins and phenolic compounds in wheat grains contribute to the antioxidant potential. Purple grain color is associated with higher anthocyanin accumulation and antioxidant capacity in wheat. Wheat mutants developed in this study may serve as a valuable source of antioxidants. © 2018 Society of Chemical Industry.

High anthocyanin accumulation in poinsettia leaves is accompanied by thylakoid membrane unstacking, acting as a photoprotective mechanism, to prevent ROS formation

In poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch.), green leaves turn reddish and then red, due to vacuolar anthocyanin accumulation. Reddish leaves accumulate anthocyanins mainly in the adaxial (upper) epidermis, and less in the mesophyll cells, while red, in both adaxial and abaxial (lower) epidermides, and the adjacent mesophyll cells. In green leaves, the photoprotective mechanism of non-photochemical quenching (NPQ) is sufficient under low light (LL), but not under high light (HL), which results in a more reduced redox state of the plastoquinone (PQ) pool compared to reddish. In red leaves, higher anthocyanin accumulation is accompanied by unstacking of thylakoid membranes that results in loss of photosystem II (PSII) complexes and undetectable hydrogen peroxide (H2O2). Superoxide dismutase (SOD) activity is enhanced in the reddish compared to green leaves, while it decreases significantly in the red ones. Anthocyanin accumulation was significantly correlated to the redox state of the PQ pool and the higher accumulation in reddish compared to green leaves was responsible for the diminished H2O2 production, since ascorbate peroxidase (APX) activity remained unchanged in all leaves. We suggest that H2O2 production regulated by the redox state of the PQ pool induces anthocyanin biosynthesis that is accompanied by thylakoid membrane unstacking and loss of PSII complexes, serving as a photoprotective mechanism to HL, preventing the formation of reactive oxygen species (ROS).

Arginine treatment attenuates chilling injury of pomegranate fruit during cold storage by enhancing antioxidant system activity

In this study, the impacts of arginine treatment at 0, 0.5, 1 and 2mM applied by preharvest spray in combination with postharvest immersion, on postharvest chilling injury and nutraceutical properties of pomegranate fruit during storage at 4±0.5°C for 120 d was investigated. Pomegranate fruit treated with arginine at 1mM, displayed significantly lower chilling injury symptom manifested by external husk browning. Lower husk browning in pomegranate fruit treated with arginine, caused by lower husk H2O2 accumulation, was partially due to higher antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activities, leading to higher membrane integrity revealed by lower electrolyte leakage and malondialdehyde (MDA) accumulation. Also, lower husk browning in pomegranate fruit treated with arginine resulted from higher husk phenylalanine ammonia-lyase (PAL)/polyphenol oxidase (PPO) enzymes activity ratio. Moreover, pomegranate fruit treated with arginine displayed higher arils DPPH scavenging capacity, due to higher arils total phenols and anthocyanins accumulation. Also, higher arils PAL/PPO enzymes activity ratio together with lower arils H2O2 accumulation was partially due to higher antioxidant enzymes, SOD, CAT and APX activities which are crucial for higher arils DPPH scavenging capacity. In addition, higher arils ascorbic acid content in pomegranate fruit treated with arginine may be attributed to higher glutathione reductase (GR)/APX system activity or higher anthocyanin accumulation. The results of this study suggest that arginine treatment can be used as promising technology not only for attenuating chilling injury but also for maintaining nutraceutical properties of pomegranate fruit partially by promoting antioxidant system activity.

Vanillylacetone up-regulates anthocyanin accumulation and expression of anthocyanin biosynthetic genes by inducing endogenous abscisic acid in grapevine tissues

We investigated the effect of vanillylacetone (VA) on anthocyanin accumulation with aim of improving grape berry coloration. Spraying Vitis vinifera cv. Muscat Bailey A berries with VA at veraison increased sugar/acid ratio, an indicator of maturation and total anthocyanin accumulation. To elucidate the molecular mechanism underlying the effect of VA on anthocyanin accumulation, in vitro VA treatment of a grapevine cell culture was carried out. Endogenous abscisic acid (ABA) content was higher in the VA-treated cell cultures than in control at 3h after treatment. Consistent with this, the relative expression levels of anthocyanin-synthesis-related genes, including DFR, LDOX, MybA1 and UFGT, in VA-treated cell cultures were much higher than those in control, and high total anthocyanin accumulation was noted in the VA-treated cell cultures as well. These results suggest that VA up-regulates the expression of genes leading to anthocyanin accumulation by inducing endogenous ABA. In addition, VA increased total anthocyanin content in a dose-dependent manner. Although VA treatment in combination with exogenous ABA did not exhibit any synergistic effect, treatment with VA alone showed an equivalent effect to that with exogenous ABA alone on total anthocyanin accumulation. These findings point to the possibility of using VA for improving grape berry coloration.

High accumulation of anthocyanins via the ectopic expression of AtDFR confers significant salt stress tolerance in Brassica napus L.

The ectopic expression of AtDFR results in increased accumulation of anthocyanins leading to enhanced salinity and drought stress tolerance in B. napus plants. Flavonoids with antioxidant effects confer many additional benefits to plants. Evidence indicates that flavonoids, including anthocyanins, protect tissues against oxidative stress from various abiotic stressors. We determined whether increases in anthocyanins increased abiotic stress tolerance in Brassica napus, because the values of B. napus L. and its cultivation area are increasing worldwide. We overexpressed Arabidopsis dihydroflavonol-4-reductase (DFR) in B. napus. Increased DFR transcript levels for AtDFR-OX B. shoots correlated with higher anthocyanin accumulation. AtDFR-OX Brassica shoots exhibited lower reactive oxygen species (ROS) accumulation than wild-type (WT) shoots under high NaCl and mannitol concentrations. This was corroborated by 3,3-diaminobenzidine staining for ROS scavenging activity in 1,1-diphenyl-2-picryl-hydrazyl assays. Shoots of the AtDFR-OX B. napus lines grown in a high salt medium exhibited enhanced salt tolerance and higher chlorophyll content than similarly grown WT plants. Our observations suggested that the AtDFR gene can be effectively manipulated to modulate salinity and drought stress tolerance by directing to high accumulation of anthocyanins in oilseed plants.

Increased Sucrose in the Hypocotyls of Radish Sprouts Contributes to Nitrogen Deficiency-Induced Anthocyanin Accumulation.

Effects of nitrogen (N) deficiency and sucrose (Suc) addition on regulation of anthocyanin biosynthesis and their relationship were investigated in this study. Radish sprouts subjected to N deficiency had 50% higher anthocyanin accumulation than when grown in Hoagland solution (a nutrient medium with all macronutrients). The contents of endogenous soluble sugars (Suc, fructose, and glucose) in the hypocotyls were also markedly increased by N limitation, with Suc showing the highest increase. Inhibition of carbohydrate biosynthesis by addition of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) also eliminated N deficiency-induced anthocyanin accumulation. The latter was further supported by the expression of anthocyanin biosynthesis related genes and decreased activities of nitrate reductase in the presence of Suc. Together our results indicate that N deficiency-induced anthocyanin accumulation was, at least partly, dependent on the increase of the soluble sugar, especially Suc. This work is the first comprehensive study on relationship between N deficiency and sugar content on anthocyanin accumulation in the hypocotyls of radish sprouts.

Gene expression analysis of bud and leaf color in tea

Purple shoot tea attributing to the high anthocyanin accumulation is of great interest for its wide health benefits. To better understand potential mechanisms involved in purple buds and leaves formation in tea plants, we performed transcriptome analysis of six green or purple shoot tea individuals from a F1 population using the Illumina sequencing method. Totally 292 million RNA-Seq reads were obtained and assembled into 112,233 unigenes, with an average length of 759 bp and an N50 of 1081 bp. Moreover, totally 2193 unigenes showed significant differences in expression levels between green and purple tea samples, with 1143 up- and 1050 down-regulated in the purple teas. Further real time PCR analysis confirmed RNA-Seq results. Our study identified 28 differentially expressed transcriptional factors and A CsMYB gene was found to be highly similar to AtPAP1 in Arabidopsis. Further analysis of differentially expressed genes involved in anthocyanin biosynthesis and transportation showed that the late biosynthetic genes and genes involved in anthocyanin transportation were largely affected but the early biosynthetic genes were less or none affected. Overall, the identification of a large number of differentially expressed genes offers a global view of the potential mechanisms associated with purple buds and leaves formation, which will facilitate molecular breeding in tea plants.

The crucial role of PpMYB10.1 in anthocyanin accumulation in peach and relationships between its allelic type and skin color phenotype.

BackgroundRed coloration of fruit skin is one of the most important traits in peach (Prunus persica), and it is mainly due to the accumulation of anthocyanins. Three MYB10 genes, PpMYB10.1, PpMYB10.2, and PpMYB10.3, have been reported as important regulators of red coloration and anthocyanin biosynthesis in peach fruit. In this study, contribution of PpMYB10.1/2/3 to anthocyanin accumulation in the fruit skin was investigated in the Japanese peach cultivars, white-skinned ‘Mochizuki’ and red-skinned ‘Akatsuki’. We then investigated the relationships between allelic type of PpMYB10.1 and skin color phenotype in 23 Japanese peach cultivars for future establishment of DNA-marker.ResultsDuring the fruit development of ‘Mochizuki’ and ‘Akatsuki’, anthocyanin accumulation was observed only in the skin of red ‘Akatsuki’ fruit in the late ripening stages concomitant with high mRNA levels of the last step gene leading to anthocyanin accumulation, UDP-glucose:flavonoid-3-O-glucosyltransferase (UFGT). This was also correlated with the expression level of PpMYB10.1. Unlike PpMYB10.1, expression levels of PpMYB10.2/3 were low in the skin of both ‘Mochizuki’ and ‘Akatsuki’ throughout fruit development. Moreover, only PpMYB10.1 revealed expression levels associated with total anthocyanin accumulation in the leaves and flowers of ‘Mochizuki’ and ‘Akatsuki’. Introduction of PpMYB10.1 into tobacco increased the expression of tobacco UFGT, resulting in higher anthocyanin accumulation and deeper red transgenic tobacco flowers; however, overexpression of PpMYB10.2/3 did not alter anthocyanin content and color of transgenic tobacco flowers when compared with wild-type flowers. Dual-luciferase assay showed that the co-infiltration of PpMYB10.1 with PpbHLH3 significantly increased the activity of PpUFGT promoter. We also found close relationships of two PpMYB10.1 allelic types, MYB10.1-1/MYB10.1-2, with the intensity of red skin coloration.ConclusionWe showed that PpMYB10.1 is a major regulator of anthocyanin accumulation in red-skinned peach and that it activates PpUFGT transcription. PpMYB10.2/3 may be involved in functions other than anthocyanin accumulation in peach. The peach cultivars having two MYB10.1-2 types resulted in the white skin color. By contrast, those with two MYB10.1-1 or MYB10.1-1/MYB10.1-2 types showed respective red or pale red skin color. These findings contribute to clarifying the molecular mechanisms of anthocyanin accumulation and generating gene-based markers linked to skin color phenotypes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0664-5) contains supplementary material, which is available to authorized users.