Anthocyanins of Coloured Wheat Genotypes in Specific Response to SalStress

Integrated metabolome and transcriptome analyses reveal the role of BoGSTF12 in anthocyanin accumulation in Chinese kale (Brassica oleracea var. alboglabra)

BACKGROUND

The vivid red, purple, and blue hues that are observed in a variety of plant fruits, flowers, and leaves are produced by anthocyanins, which are naturally occurring pigments produced by a series of biochemical processes occurring inside the plant cells. The purple-stalked Chinese kale, a popular vegetable that contains anthocyanins, has many health benefits but needs to be investigated further to identify the genes involved in the anthocyanin biosynthesis and translocation in this vegetable.

RESULTS

In this study, the purple- and green-stalked Chinese kale were examined using integrative transcriptome and metabolome analyses. The content of anthocyanins such as cyanidin-3-O-(6″-O-feruloyl) sophoroside-5-O-glucoside, cyanidin-3,5-O-diglucoside (cyanin), and cyanidin-3-O-(6″-O-p-hydroxybenzoyl) sophoroside-5-O-glucoside were considerably higher in purple-stalked Chinese kale than in its green-stalked relative. RNA-seq analysis indicated that 23 important anthocyanin biosynthesis genes, including 3 PAL, 2 C4H, 3 4CL, 3 CHS, 1 CHI, 1 F3H, 2 FLS, 2 F3'H, 1 DFR, 3 ANS, and 2 UFGT, along with the transcription factor BoMYB114, were significantly differentially expressed between the purple- and green-stalked varieties. Results of analyzing the expression levels of 11 genes involved in anthocyanin production using qRT-PCR further supported our findings. Association analysis between genes and metabolites revealed a strong correlation between BoGSTF12 and anthocyanin. We overexpressed BoGSTF12 in Arabidopsis thaliana tt19, an anthocyanin transport mutant, and this rescued the anthocyanin-loss phenotype in the stem and rosette leaves, indicating BoGSTF12 encodes an anthocyanin transporter that affects the accumulation of anthocyanins.

CONCLUSION

This work represents a key step forward in our understanding of the molecular processes underlying anthocyanin production in Chinese kale. Our comprehensive metabolomic and transcriptome analyses provide important insights into the regulatory system that controls anthocyanin production and transport, while providing a foundation for further research to elucidate the physiological importance of the metabolites found in this nutritionally significant vegetable.

Halotolerant and plant growth-promoting endophytic fungus Aspergillus terreus CR7 alleviates salt stress and exhibits genoprotective effect in Vigna radiata

Soil salinity is one of the major environmental stresses that results in reduction of cultivable land and decreased productivity. In the present study, halotolerant and plant growth-promoting endophytic fungi were isolated from Catharanthus roseus, and their effect in mitigating salt stress in Vigna radiata was evaluated. An isolate CR7, identified to be Aspergillus terreus, showing plant growth promotion activities, viz. IAA production (23.43 ± 0.79 μg/ml), phosphate solubilization (133.63 ± 6.40 μg/ml), ACC deaminase activity (86.36 ± 2.70 μmol α-ketobutyrate/h/mg protein) etc. and ability to grow at 15% NaCl was selected for further in vivo studies. Colonization of CR7 was carried out in V. radiata which was subjected to different concentrations of salt (150, 200, and 250 mM NaCl). Under salt stress, A. terreus CR7 inoculated plants showed substantially improved root and shoot length, biomass, chlorophyll content, relative water content, phenolics, protein content, and DPPH scavenging activity. Endogenous IAA level was enhanced by 5.28-fold in treated plants at maximum salt stress. Inoculation of A. terreus CR7 affected oxidative stress parameters, exhibiting an increase in catalase and superoxide dismutase and reduction in proline, electrolyte leakage, and malondialdehyde content. Fluorescent microscopic analysis of roots revealed improved cell viability and decreased levels of glutathione and hydrogen peroxide under salt stress in treated plants. The isolate A. terreus CR7 also protected against DNA damage induced by salt stress which was evaluated using comet assay. A decrease in DNA tail length, tail moment, and olive tail moment to the extent of 19.87%, 19.76%, and 24.81%, respectively, was observed in A. terreus CR7-colonized plants under salt stress. It can be concluded that A. terreus CR7 can be exploited for alleviating the impact of salt stress in crop plants.

The Role of Anthocyanins in Plant Tolerance to Drought and Salt Stresses

Drought and salinity affect various biochemical and physiological processes in plants, inhibit plant growth, and significantly reduce productivity. The anthocyanin biosynthesis system represents one of the plant stress-tolerance mechanisms, activated by surplus reactive oxygen species. Anthocyanins act as ROS scavengers, protecting plants from oxidative damage and enhancing their sustainability. In this review, we focus on molecular and biochemical mechanisms underlying the role of anthocyanins in acquired tolerance to drought and salt stresses. Also, we discuss the role of abscisic acid and the abscisic-acid-miRNA156 regulatory node in the regulation of drought-induced anthocyanin production. Additionally, we summarise the available knowledge on transcription factors involved in anthocyanin biosynthesis and development of salt and drought tolerance. Finally, we discuss recent progress in the application of modern gene manipulation technologies in the development of anthocyanin-enriched plants with enhanced tolerance to drought and salt stresses.

Thiocyanate-degrading microflora alleviates thiocyanate stress on tomato seedlings by improving plant and rhizosphere microenvironment

Thiocyanate in irrigation water can adversely affect plant growth and development. A previously constructed microflora with effective thiocyanate-degrading ability was used to investigate the potential of bacterial degradation for thiocyanate bioremediation. The root and aboveground part dry weight of plants inoculated with the degrading microflora increased by 66.67% and 88.45%, respectively, compared to those plants without the microflora. The supplementation of thiocyanate-degrading microflora (TDM) significantly alleviated the interference of thiocyanate in mineral nutrition metabolism. Moreover, the supplementation of TDM significantly reduced the activities of antioxidant enzymes, lipid peroxidation, and DNA damage and it protected plants from excessive thiocyanate, while the crucial antioxidant enzyme (peroxidase) decreased by 22.59%. Compared with the control without TDM supplementation, the soil sucrase content increased by 29.58%. The abundances of Methylophilus, Acinetobacter, unclassified Saccharimonadales, and Rhodanobacter changed from 19.92%, 6.63%, 0.79%, and 3.90%-13.19%, 0.27%, 3.06%, and 5.14%, respectively, with TDM supplementation. Caprolactam, 5,6-dimethyldecane, and pentadecanoic acid seem to have an effect on the structure of the microbial community in the rhizosphere soil. The above results indicated TDM supplementation can significantly reduce the toxic effects of thiocyanate on the tomato-soil microenvironment.

Genetic Mapping of Flavonoid Grain Pigments in Durum Wheat

Pigmented cereal grains with high levels of flavonoid compounds have attracted the attention of nutritional science backing the development of functional foods with claimed health benefits. In this study, we report results on the genetic factors controlling grain pigmentation in durum wheat using a segregant population of recombinant inbred lines (RILs) derived from a cross between an Ethiopian purple grain accession and an Italian amber grain cultivar. The RIL population was genotyped by the wheat 25K SNP array and phenotyped for total anthocyanin content (TAC), grain color, and the L*, a*, and b* color index of wholemeal flour, based on four field trials. The mapping population showed a wide variation for the five traits in the different environments, a significant genotype x environment interaction, and high heritability. A total of 5942 SNP markers were used for constructing the genetic linkage map, with an SNP density ranging from 1.4 to 2.9 markers/cM. Two quantitative trait loci (QTL) were identified for TAC mapping on chromosome arms 2AL and 7BS in the same genomic regions of two detected QTL for purple grain. The interaction between the two QTL was indicative of an inheritance pattern of two loci having complementary effects. Moreover, two QTL for red grain color were detected on chromosome arms 3AL and 3BL. The projection of the four QTL genomic regions on the durum wheat Svevo reference genome disclosed the occurrence of the candidate genes Pp-A3, Pp-B1, R-A1, and R-B1 involved in flavonoid biosynthetic pathways and encoding of transcription factors bHLH (Myc-1) and MYB (Mpc1, Myb10), previously reported in common wheat. The present study provides a set of molecular markers associated with grain pigments useful for the selection of essential alleles for flavonoid synthesis in durum wheat breeding programs and enhancement of the health-promoting quality of derived foods.

Investigation of the Key Genes Associated with Anthocyanin Accumulation during Inner Leaf Reddening in Ornamental Kale (Brassica oleracea L. var. acephala)

Ornamental kale (Brassica oleracea L. var. acephala) is a popular decorative plant in late autumn and winter. However, only during low-temperature color-changed periods below rough 15 °C can the plant accumulate anthocyanins and exhibit a diverse array of foliar color patterns. In this study, we probed into the potential mechanism of inner leaf reddening in a red-leaf pure line of ornamental kale by physiological, metabolic, and transcriptomic analyses. Determination of anthocyanin contents in the uncolored new white leaves (S0), the light red leaves (S1) in the reddening period and the red leaves (S2) completing color change, and analysis of anthocyanin metabolites at stage S2, revealed that the coloring of red leaves was mainly attributed to the accumulation of cyanidins. We further used transcriptomic sequencing between the pairwise S0, S1, and S2 stages to identify 21 differentially expressed genes (DEGs) involved in anthocyanin biosynthesis, among which the expression level of 14 DEGs was positively correlated with anthocyanin accumulation, and 6 DEGs were negatively correlated with anthocyanin accumulation. A total of 89 co-expressed genes were screened out, from which three DEGs (BoCHI, Bo4CL3, and BoF3H) were identified as hub genes in co-expression DEGs network. BoDFR and BoCHI were the DEGs with the highest expressions at S2. Moreover, two co-expressed DEGs related to stress response (BoBBX17 and BoCOR47) also exhibited upregulated expressions and positive correlations with anthocyanin accumulation. A deep dive into the underlying regulatory network of anthocyanin accumulation comprising these six upregulated DEGs from S0 to S2 was performed via trend, correlation, and differentially co-expression analysis. This study uncovered the DEGs expression profiles associated with anthocyanin accumulation during ornamental kale inner leaf reddening, which provided a basis for further dissecting the molecular mechanisms of leaf color characteristic change in ornamental kale at low temperatures.

Development of High-Fibre, Ready-to-Bake Flour Mixtures from Purple Wheat

Nowadays, consumers are paying more and more attention to healthy eating, and unfortunately, insulin resistance and type 2 diabetes are affecting many people. In general, people are paying more attention to the consumption of fibre-rich foods. In our study, we developed high-fibre ready-to-bake flour mixture blends using purple wheat flour (white and wholemeal). For fibre fortification, inulin, chia seed flour and psyllium husk flour were used. After determining the basic nutritional parameters of the raw materials, four series of experiments were carried out to prepare bread rolls and to test the finished products. The correct mixing ratio of the enriching agents were tested, and the final flour mixtures were tested. At the end of our research, three blends (white purple wheat flour + 4% inulin + 2% psyllium husk flour; wholemeal purple wheat flour + white purple wheat flour + 4% inulin + 4% chia seed flour; wholemeal purple wheat flour + 4% inulin + 4% chia seed flour) were developed.

Protective and defensive role of anthocyanins under plant abiotic and biotic stresses: An emerging application in sustainable agriculture

Global warming is the major cause of abiotic and biotic stresses that reduce plant growth and productivity. Various stresses such as drought, low temperature, pathogen attack, high temperature and salinity all negatively influence plant growth and development. Due to sessile beings, they cannot escape from these adverse conditions. However, plants develop a variety of systems that can help them to tolerate, resist, and escape challenges imposed by the environment. Among them, anthocyanins are a good example of stress mitigators. They aid plant growth and development by increasing anthocyanin accumulation, which leads to increased resistance to various biotic and abiotic stresses. In the primary metabolism of plants, anthocyanin improves the photosynthesis rate, membrane permeability, up-regulates many enzyme transcripts related to anthocyanin biosynthesis, and optimizes nutrient uptake. Generally, the most important genes of the anthocyanin biosynthesis pathways were up-regulated under various abiotic and biotic stresses. The present review will highlight anthocyanin mediated stress tolerance in plants under various abiotic and biotic stresses. We have also compiled literature related to genetically engineer stress-tolerant crops generated using over-expression of genes belonging to anthocyanin biosynthetic pathway or its regulation. To sum up, the present review provides an up-to-date description of various signal transduction mechanisms that modulate or enhance anthocyanin accumulation under stress conditions.

Proteomic Approaches to Uncover Salt Stress Response Mechanisms in Crops

Salt stress is an unfavorable outcome of global climate change, adversely affecting crop growth and yield. It is the second-biggest abiotic factor damaging the morphological, physio-biochemical, and molecular processes during seed germination and plant development. Salt responses include modulation of hormonal biosynthesis, ionic homeostasis, the antioxidant defense system, and osmoprotectants to mitigate salt stress. Plants trigger salt-responsive genes, proteins, and metabolites to cope with the damaging effects of a high salt concentration. Enhancing salt tolerance among crop plants is direly needed for sustainable global agriculture. Novel protein markers, which are used for crop improvement against salt stress, are identified using proteomic techniques. As compared to single-technique approaches, the integration of genomic tools and exogenously applied chemicals offers great potential in addressing salt-stress-induced challenges. The interplay of salt-responsive proteins and genes is the missing key of salt tolerance. The development of salt-tolerant crop varieties can be achieved by integrated approaches encompassing proteomics, metabolomics, genomics, and genome-editing tools. In this review, the current information about the morphological, physiological, and molecular mechanisms of salt response/tolerance in crops is summarized. The significance of proteomic approaches to improve salt tolerance in various crops is highlighted, and an integrated omics approach to achieve global food security is discussed. Novel proteins that respond to salt stress are potential candidates for future breeding of salt tolerance.

Changes in the physicochemical parameters and microbial community of a new cultivar blue wheat cereal wholemeal during sourdough production

Changes in the characteristics of a new cultivar (DS8472-5) of blue wheat during wholemeal fermentation with Pediococcus acidilactici (LUHS29), Liquorilactobacillus uvarum (LUHS245), and Lactiplantibacillus plantarum (LUHS122), including acidity, microbiological and chromaticity parameters, free amino acid (FAA), gamma-aminobutyric acid (GABA), and biogenic amine (BA) contents, macro- and micro-element concentrations and fatty acid (FA) and volatile compounds (VC), were evaluated. In addition, a metagenomic analysis was performed. The lactic acid bacteria (LAB) strains used for fermentation was a significant factor in wholemeal fermentation sample pH, redness (a*) and LAB counts (p ≤ 0.05). In most of the samples, fermentation increased the FAA content in wheat wholemeal, and the highest concentration of GABA was found in DS8472-5 LUHS122 samples. Phenylethylamine (PHE) was found in all wheat wholemeal samples; however, spermidine was only detected in fermented samples and cadaverine only in DS8472-5 LUHS122. Fermented samples showed higher omega-3 and omega-6 contents and a higher number and variety of VC. Analysis of the microbial profile showed that LAB as part of the natural microbiota present in cereal grains also actively participates in fermentation processes induced by industrial bacterial cultures. Finally, all the tested LAB were suitable for DS8472-5 wheat wholemeal fermentation, and the DS8472-5 LUHS122 samples showed the lowest pH and the highest LAB viable counts (3.94, 5.80°N, and 8.92 log10 CFU/g, respectively).

The Potential of Traditional ‘Gaja’ and New Breed Lines of Waxy, Blue and Purple Wheat in Wholemeal Flour Fermentation

The aim of this study was to analyse and compare the acidity, microbiological and colour characteristics, fatty (FA) and amino (AA) acid profiles, biogenic amine (BA) and gamma-aminobutyric acid (GABA) concentrations, and macro- and microelement contents in non-treated (non-fermented) and fermented wholemeal cereal flours of ‘Gaja’ (traditional wheat) and new breed lines DS8888-3-6 (waxy wheat), DS8548-7 (blue wheat) and DS8535-2 (purple wheat). Independent fermentations were undertaken with selected strains of Pediococcus acidilactici, Liquorilactobacillus uvarum and Lactiplantibacillus plantarum. The results revealed that all the wholemeal cereal flours of the analysed wheat varieties are suitable for fermentation with the selected strains because all the fermented samples showed lactic acid bacteria (LAB) viable counts higher than 8.00 log10 CFU/g and desirable low pH values. In most of the cases, fermentation increased the concentration of essential amino acids in the wholemeal cereal samples, and the LAB strain used for fermentation proved to be a significant factor in all the essential amino acid content of wholemeal wheat (p ≤ 0.0001). When comparing the non-fermented samples, the highest GABA content was found in ‘Gaja’ and waxy wheat samples (2.47 µmol/g, on average), and, in all the cases, fermentation significantly increased GABA concentration in the wholemeal cereals. On the other hand, total levels of biogenic amines in wholemeal samples ranged from 22.7 to 416 mg/kg. The wheat variety was a significant factor in all the analysed macro- and microelement contents (p ≤ 0.0001) in the wholemeal cereals. Furthermore, fermentation showed to be a significant factor in most of the FA content of the wholemeal cereal samples. Finally, fermentation can also contribute to improving the biological and functional value of wholemeal wheat flours (by increasing essential amino acids and GABA concentrations); however, safety parameters (e.g., biogenic amines) also should be taken into consideration when optimizing the most appropriate technological parameters.

The roles of HD-ZIP proteins in plant abiotic stress tolerance

Homeodomain leucine zipper (HD-ZIP) proteins are plant-specific transcription factors that contain a homeodomain (HD) and a leucine zipper (LZ) domain. The highly conserved HD binds specifically to DNA and the LZ mediates homodimer or heterodimer formation. HD-ZIP transcription factors control plant growth, development, and responses to abiotic stress by regulating downstream target genes and hormone regulatory pathways. HD-ZIP proteins are divided into four subclasses (I-IV) according to their sequence conservation and function. The genome-wide identification and expression profile analysis of HD-ZIP proteins in model plants such as Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa) have improved our understanding of the functions of the different subclasses. In this review, we mainly summarize and discuss the roles of HD-ZIP proteins in plant response to abiotic stresses such as drought, salinity, low temperature, and harmful metals. HD-ZIP proteins mainly mediate plant stress tolerance by regulating the expression of downstream stress-related genes through abscisic acid (ABA) mediated signaling pathways, and also by regulating plant growth and development. This review provides a basis for understanding the roles of HD-ZIP proteins and potential targets for breeding abiotic stress tolerance in plants.

Effect of Salinity and Plant Growth Promoters on Secondary Metabolism and Growth of Milk Thistle Ecotypes

Simple Summary

The present study shed light on the effect of salinity on the plant growth and secondary metabolites of medicinally important milk thistle plant ecotypes. At the same time, we also studied the effect of external supplementation with ascorbic acid, thiourea, and moringa leaf extract on improving growth-related attributes and secondary metabolites under salinity stress. Various parameters were studied related to stress alleviation. Ascorbic acid, followed by moringa leaf extract, was the most effective in improving growth under salt stress conditions. The present study demonstrated that milk thistle could withstand moderate doses of salt stress, while externally supplemented media improved all the growth parameters by increasing the accumulation of secondary metabolites.

Abstract

Milk thistle (Silybum marianum (L.)) is a wild medicinal herbal plant that is widely used in folk medicine due to its high content of secondary metabolites (SMs) and silymarin; however, the data regarding the response of milk thistle to salinity are still scarce and scanty. The present study evaluated the effect of salinity on a geographically diverse population of milk thistle and on the role of medium supplementation (MS) with ascorbic acid, thiourea, and moringa leaf extract in improving the SMs and growth-related attributes under salinity stress (SS). For germination, a 120 mM level of salinity was applied in the soil during the seedling stage. After salinity development, predetermined levels of the following compounds were used for MS: thiourea (250 µM), moringa leaf extract (3%), and ascorbic acid (500 µM). The data regarding growth attributes showed that SS impaired plant growth and development and increased SM production, including alkaloids, anthocyanin, and saponins. Moreover, ascorbic acid, followed by moringa leaf extract, was the most effective in improving growth by virtue of increased SMs, especially under salt stress conditions. The present study demonstrated that milk thistle could withstand moderate doses of SS, while MS improved all the growth parameters by increasing the accumulation of SMs.

Stability Enhancement of Anthocyanins from Blackcurrant (Ribes Nigrum L.) Pomace through Intermolecular Copigmentation

Intermolecular copigmentation denotes the interaction between colored anthocyanins and the colorless copigment, which is not bound covalently to the anthocyanin molecule. This is the first study to investigate the effect of intermolecular copigmentation on the stability of individual anthocyanins from dried blackcurrant pomace (DBP) using four pure phenolic acids as copigments (ferulic, caffeic, chlorogenic, and rosmarinic acid). Studies were performed at pH 3.0 and pH 6.0, with a copigment/anthocyanin extract molar ratio of 5:1, during storage at 20 °C. At both pH 3.0 and 6.0, rosmarinic acid showed the strongest hyperchromic and bathochromic effects (p < 0.05) on day 0. However, rosmarinic acid showed low stability during storage. At pH 3.0, chlorogenic acid and control samples were capable of maintaining very high levels of total anthocyanin stability during storage (p < 0.05). On the other hand, ferulic acid and control samples had the longest estimated half-life during storage at pH 6.0. Intermolecular copigmentation successfully increased the half-life, color retention, and antioxidant activity of the anthocyanin solution, with cyanidin-3-O-glucoside (C3G) exhibiting the highest stability at both pH values. Overall, anthocyanins from DBP, in combination with chlorogenic or ferulic acid, showed potential for use in commercial food applications.

Elicitation of the in vitro Cultures of Selected Varieties of Vigna radiata L. With Zinc Oxide and Copper Oxide Nanoparticles for Enhanced Phytochemicals Production

This study was conducted to develop a protocol for in vitro shoot multiplication and callus induction of various mung bean varieties to obtain enhanced phytochemical content with the help of elicitors. For shoot multiplication, two types of explants (shoot tips and nodal tips) of three varieties of mung bean (Mung NCM-13, MgAT-7, and MgAT-4) were used. Both types of explants from in vitro and in vivo sources were cultured on the MS medium supplemented with different concentrations (0.25-3.0 mg/L, increment of 0.5 mg/L) and combinations of BAP and IBA as independent treatments. For callus induction, leaf explants (in vitro source) were cultured on MS medium supplemented with 2,4-D (1-3 mg/L) alone or in combination with BAP or NAA (0.5 and 1.0 mg/L). For the enhanced production of phenolics and glycosides, calli were cultured on MS media supplemented with zinc oxide (0.5 mg/L) and copper oxide nanoparticles (0.5 mg/L) as nano-elicitors. Results showed that in vitro explants responded better in terms of shoot length, number of shoots, and number of leaves per explant when compared to in vivo explants. Moreover, shoot tips were better than nodal explants to in vitro culturing parameters. All three varieties showed the optimized results in the MS medium supplemented with 1 mg/L BAP, while roots were produced only in cultures fortified with 1 mg/L IBA. The leaf explants of in vitro and soil-grown plantlets showed a maximum callogenic response of 90 and 80%, respectively, on MS medium supplemented with 2,4-D (3 mg/ml). Maximum phenolic content (101.4 μg of gallic acid equivalent/g) and glycoside content (34 mg of amygdalin equivalent/g of plant material) was observed in the calli cultured on MS medium supplemented with 3 mg/L of 2,4-D. Furthermore, the addition of zinc oxide (0.5 mg/L) and copper oxide (0.5 mg/L) nanoparticles to the callus culture medium significantly enhanced the phenolic content of Mung NCM-13 (26%), MgAT-7 (25.6%), and MgAT-4 (22.7%). Glycosidic content was also found to be increased in Mung NCM-13 (50%), MgAT-7 (37.5%), and MgAT-4 (25%) varieties when compared to the control. It is suggested that elicitation of in vitro cultures of mung beans with nanoparticles could be an effective strategy for the enhanced production of secondary metabolites.

Rising Demand for Healthy Foods-Anthocyanin Biofortified Colored Wheat Is a New Research Trend

Wheat is a vital and preferred energy source in many parts of the world. Its unique processing quality helps prepare many products such as bread, biscuit, pasta, and noodles. In the world of rapid economic growth, food security, in terms of nutritional profile, began to receive more significant interest. The development of biofortified colored wheat (black, purple, and blue) adds nutritional and functional health benefits to the energy-rich wheat. Colored wheat exists in three forms, purple, blue, and black, depending upon the types and position of the anthocyanins in wheat layers, regulated by the bHLH-MYC transcription factor. Colored wheat lines with high anthocyanin, iron, and zinc contents showed antioxidant and anti-inflammatory activity and possessed desirable product-making and commercial utilization features. The anthocyanin in colored wheat also has a broad spectrum of health implications, such as protection against metabolic syndromes like obesity, diabetes, hypertension, and dyslipidemia. The idea of developing anthocyanin-biofortified wheat shapes human beings' lifestyles as it is a staple food crop in many parts of the world. This review is a compilation of the currently available information on colored wheat in the critical aspects, including biochemistry, food processing, nutrition, genetics, breeding, and its effect on human health. Market generation and consumer awareness creation are vital challenges for its exploitation as a function food on a large scale.

Analyses on the pigment composition of different seed coat colors in adzuki bean

Seed coat color is an important quality and domestication trait. The adzuki bean has more than a dozen seed coat colors closely associated with the anthocyanin and flavonoid metabolism pathways. In this study, we explored the pigment composition of 10 different seed coat color adzuki beans including red, black mottle on red, black mottle on gray, golden, green, black, ivory, brown, and light brown. The results showed that anthocyanins are the main pigment in adzuki bean seed coat. There were no carotenoid or pelargonidin derivatives in the seed coats of any accessions. Different colors of adzuki bean seed coat have different pigment compositions and the combination of procyanidins and anthocyanins affected seed coat color. The ivory seed coat had an extremely low proanthocyanidin and anthocyanin content. Only the green adzuki bean seed coats contained chlorophyll. Our results explain the pigment composition of the different seed coat colors and the combination of proanthocyanidins and anthocyanins affected seed coat color in adzuki bean. These results can provide a theoretical basis for the study of adzuki bean coloring mechanism.

Anthocyanin Biosynthesis and a Regulatory Network of Different-Colored Wheat Grains Revealed by Multiomics Analysis

Colored wheat has always been a popular research area because of its high performance in the field and significant medical uses. Progress has been made mapping the genes of purple or blue grains; however, the reason why different grain colors form in wheat is not well understood. We created wheat lines with different grain colors (purple and blue) using the white grain cultivar Xiaoyan22 and located the candidate region related to the purple and blue grains in chromosome 2A, 2B, and 4D, 2A, respectively, by the bulked segregant RNA-seq. The transcriptomic and metabolomic analyses of the three grains at different developmental stages indicated that the upregulation of flavonoid 3'-hydroxylase/flavonoid 3',5'hydroxylase 2 and TaMYC1/TaMYC4 was important for the formation of purple/blue grains. The blue TaMYC4 had 16 nonsynonymous single nucleotide variants verified by Sanger sequencing and possessed a different splicing mode in the bHLH_MYC_N domain compared with the reference database. Targeted high-performance liquid chromatography-mass spectrometry/mass spectrometry analysis of anthocyanins found that the purple and blue grains contained more pelargonidin, cyanidin, and delphinidin, respectively. This study provides a comprehensive understanding of the different color formations of wheat grains and useful information about genetic improvements in wheat and other crops.

Salt Stress Alleviation in Triticum aestivum Through Primary and Secondary Metabolites Modulation by Aspergillus terreus BTK-1

We report the growth promoting potential in wheat under saline conditions by an endophytic fungus Aspergillus terreus BTK-1. The isolated BTK-1 from the root of Chenopodium album was identified as Aspergillus terreus through 18S rDNA sequence analysis. BTK-1 secreted indole acetic acid (IAA), exhibited 1- aminocyclopropane-1- carboxylate deaminase (ACC) and siderophores activity, and solubilized phosphate. Wheat seedlings were exposed to a saline environment (0, 60, 120, and 180 mM) with or without BKT-1 inoculation. Seedlings inoculated with BTK-1 showed higher concentrations of IAA and gibberellins, whereas they showed low concentrations of abscisic acid compared to the BTK-1 non-inoculated plants. Also, BTK-1 inoculated wheat plants revealed significantly (P = 0.05) longer shoots and roots, biomass, and chlorophyll contents. On the contrary, plants without BTK-1 inoculation indicated significantly (P = 0.05) low amounts of carbohydrates, phenolics, prolines, potassium, magnesium, and calcium, with high amounts of Na and malonaldehyde under salt stress. Likewise, BTK-1 inoculated wheat plants showed high activity of reduced glutathione, and low activity of ascorbate, catalase, and peroxidase under salt stress. The mitigation of salinity stress by BTK-1 inoculated wheat plants suggested its use as a bio-stimulator in salt affected soils.

Physiological and molecular response of colored wheat seedlings against phosphate deficiency is linked to accumulation of distinct anthocyanins

Anthocyanin rich colored wheat with additional health benefits has created interest among breeders, consumers and policy makers to address the prevailing malnutrition in the vulnerable population. Researchers are exploring how colored wheat could perform under different nutrient conditions for the maintenance of growth and development. The present study was aimed to investigate the differential response of phosphorous (Pi) deficiency at the seedling stage using hydroponics. Our results showed that Pi-deficiency triggered typical response in the wheat along with the changes in the plant root morphology, total biomass, micronutrient concentration and distinct anthocyanin accumulation. Our physiological and biochemical data revealed that these parameters were positively altered under stress in the colored wheat and the adaptation followed the trend of white < blue <purple < black. Our results also confirmed that stress induced accumulation of distinct anthocyanins including derivatives of cyanidin, delphinidin and peonidin in a genotype dependent manner. Differential expression pattern visualized for the transcripts encoding phosphate transporters, anthocyanin biosynthesis, putative transporters and regulators may be one of the underlying factors. Altogether, our data showed that the black wheat genotype with highest anthocyanin content could able to adapt better with the P stress. This study will help in identifying suitable colored wheat adapting the stress condition and have potential for influence on the future agricultural cultivation practices.

Electron and proton transport in wheat exposed to salt stress: is the increase of the thylakoid membrane proton conductivity responsible for decreasing the photosynthetic activity in sensitive genotypes?

Effects of salinity caused by 150 mM NaCl on primary photochemical reactions and some physiological and biochemical parameters (K⁺/Na⁺ ratio, soluble sugars, proline, MDA) have been studied in five Triticum aestivum L. genotypes with contrasting salt tolerance. It was found that 150 mM NaCl significantly decreased the photosynthetic efficiency of two sensitive genotypes. The K⁺/Na⁺ ratio decreased in all genotypes exposed to salinity stress when compared with the control. Salinity stress also caused lipid peroxidation and accumulation of soluble sugars and proline. The amounts of soluble sugars and proline were higher in tolerant genotypes than sensitive ones, and lipid peroxidation was higher in sensitive genotypes. The noninvasive measurements of photosynthesis-related parameters indicated the genotype-dependent effects of salinity stress on the photosynthetic apparatus. The significant decrease of chlorophyll content (SPAD values) or adverse effects on photosynthetic functions at the PSII level (measured by the chlorophyll fluorescence parameters) were observed in the two sensitive genotypes only. Although the information obtained by different fast noninvasive techniques were consistent, the correlation analyses identified the highest correlation of the noninvasive records with MDA, K⁺/Na⁺ ratio, and free proline content. The lower correlation levels were found for chlorophyll content (SPAD) and F_v/F_m values derived from chlorophyll fluorescence. Performance index (PI_abs) derived from fast fluorescence kinetics, and F₇₃₅/F₆₈₅ ratio correlated well with MDA and Na⁺ content. The most promising were the results of linear electron flow measured by MultispeQ sensor, in which we found a highly significant correlation with all parameters assessed. Moreover, the noninvasive simultaneous measurements of chlorophyll fluorescence and electrochromic band shift using this sensor indicated the apparent proton leakage at the thylakoid membranes resulting in a high proton conductivity (gH⁺), present in sensitive genotypes only. The possible consequences for the photosynthetic functions and the photoprotection are discussed.

Transcript profiling of stress-responsive genes and metabolic changes during salinity in indica and japonica rice exhibit distinct varietal difference

In the present study, we carried out comprehensive transcript profiling of diverse genes under salinity (200 mM NaCl) at different time points, accompanied by certain biochemical alterations of the indica (IR-64 and Pokkali) and japonica (Nipponbare and M-202) rice. The higher susceptibility of Nipponbare and IR-64 was reflected by lower relative water content, chlorophyll loss, higher malondialdehyde content, and accumulation of H₂ O₂ , and reduced nitrate reductase activity, compared to M-202 and Pokkali, where such changes were less pronounced. Enhanced levels of anthocyanins and reduced glutathione, together with elevated phenylalanine ammonia lyase activity, mainly conferred protection to Nipponbare and IR-64, while metabolites like phenolics, flavonoids, proline, and polyamines were more induced in M-202 and Pokkali. Varietal differences in the expression pattern of diverse groups of genes during different durations (6, 24, and 48 h) of stress were striking. A gene showing early induction for a particular variety exhibited a delayed induction in another variety or a gradually decreased expression with treatment time. Pokkali was clearly identified as the salt-tolerant genotype among the examined varieties based on increased antioxidant potential and enhanced expression of genes encoding for PAL, CHS, and membrane transporters like SOS3, NHX-1, and HKT-1. The results presented in this work provide insight into the complex varying regulation patterns for different genes across the investigated rice varieties in providing salt tolerance and highlights distinct differences in expression patterns between susceptible and tolerant indica and japonica rice.

A Review of Recent Advances and Future Directions in the Management of Salinity Stress in Finger Millet

Salinity stress is a major environmental impediment affecting the growth and production of crops. Finger millet is an important cereal grown in many arid and semi-arid areas of the world characterized by erratic rainfall and scarcity of good-quality water. Finger millet salinity stress is caused by the accumulation of soluble salts due to irrigation without a proper drainage system, coupled with the underlying rocks having a high salt content, which leads to the salinization of arable land. This problem is projected to be exacerbated by climate change. The use of new and efficient strategies that provide stable salinity tolerance across a wide range of environments can guarantee sustainable production of finger millet in the future. In this review, we analyze the strategies that have been used for salinity stress management in finger millet production and discuss potential future directions toward the development of salt-tolerant finger millet varieties. This review also describes how advanced biotechnological tools are being used to develop salt-tolerant plants. The biotechnological techniques discussed in this review are simple to implement, have design flexibility, low cost, and highly efficient. This information provides insights into enhancing finger millet salinity tolerance and improving production.

EkFLS overexpression promotes flavonoid accumulation and abiotic stress tolerance in plant

Flavonoids with great medicinal value play an important role in plant individual growth and stress resistance. Flavonol synthetase (FLS) is one of the key enzymes to synthesize flavonoids. However, the role of the FLS gene in flavonoid accumulation and tolerance to abiotic stresses, as well as its mechanism has not yet been investigated systematically in plants. The aim of this research is to evaluate the effect of FLS overexpression on the accumulation of active ingredients and stress resistance in Euphorbia kansui Liou. The results showed that when the EkFLS gene was overexpressed in Arabidopsis thaliana, the accumulation of flavonoids was improved. In addition, when the wild-type and EkFLS overexpressed Arabidopsis plants were treated with ABA and MeJA, compared with WT Arabidopsis, EkFLS overexpressed Arabidopsis promoted stomatal aperture to influence photosynthesis of the plants, which in turn can promote stress resistance. Meanwhile, under MeJA, NaCl, and PEG treatment, EkFLS overexpressed in Arabidopsis induced higher accumulation of flavonoids, which significantly enhanced peroxidase (POD) and superoxide dismutase (SOD) activities that can scavenge reactive oxygen species in cells to protect the plant. These results indicated that EkFLS overexpression is strongly correlated to the increase of flavonoid synthesis and therefore the tolerance to abiotic stresses in plants, providing a theoretical basis for further improving the quality of medicinal plants and their resistance to abiotic stresses simultaneously.

Transcriptomic and metabolomic profiling reveals the protective role of anthocyanins in alleviating low phosphate stress in maize

Anthocyanin accumulation is a characteristic response to phosphate (Pi) deficiency in plants. In the present study, we investigated the role of maize anthocyanins (MA) in alleviating low Pi (LP) stress in maize (Zea mays L). To this end, maize plants were exposed to LP conditions and treated with or without (control) MA. Interestingly, MA-treated maize plants showed relieved growth inhibition, reproductive development retardation, and yield loss compared to control plants under LP stress. Moreover, the level of oxidative destruction was significantly alleviated in MA-treated plants compared to the untreated control under conditions of LP stress. Acid phosphatase (APase) activity was significantly higher in MA-treated plants than in control plants, resulting in enhanced Pi mobilization and recycling. The results of the transcriptome analysis suggested that genes involved in photosynthesis, photosystem light harvesting, Pi transport, and recycling were differentially expressed between MA-treated plants and control plants. Moreover, metabolome analysis indicated higher sugar and organic acid levels and lower phosphorylated metabolite contents in MA-treated plants than in control plants, which was consistent with the results of the comparative transcriptome analysis. Taken together, our findings indicate that MA plays critical roles in alleviating LP stress in maize plants, probably by improving photosynthetic performance and increasing Pi mobilization and recycling.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12298-021-00981-9.

Genetic variation and gene expression of anthocyanin synthesis and transport related enzymes in Oryza sativa against thiocyanate

Plants exposed to environmental contaminants often synthesize anthocyanins (ATHs) as an approach to safeguard themselves from adverse impact. However, the overload of ATHs in plant cells can threaten their growth and development through proteins oxidization and intercalating with DNAs inside cells. In the present study, a microcosm hydroponic experiment was conducted using rice seedlings to investigate the molecular signaling pathways involved in regulating and controlling ATHs synthesis and transport exposed to thiocyanate (SCN^-). Our results indicated that SCN^- exposure significantly (p < 0.05) increased the expression of ATHs synthesis related genes (i.e., PAL, CHS, ANS, UFGT genes) in rice tissues, altered the activities of these ATHs synthesis related enzymes, and consequently elevated the ATHs content. However, SCN^- exposure significantly decreased the expression of ATHs transport related genes (i.e., GST, ABC, MATE genes) in rice seedlings, suggesting that SCN^- exposure have restrained ATHs transport from cytosol to vacuole in cells, eventually posing a significant adverse effect on cells survival. Our findings highlight on one of the plant aspects in managing the toxicity triggered by secondary metabolites under stress conditions.

Production of Betacyanins in Transgenic Nicotiana tabacum Increases Tolerance to Salinity

Although red betalain pigments (betacyanins) have been associated with salinity tolerance in some halophytes like Disphyma australe, efforts to determine whether they have a causal role and the underlying mechanisms have been hampered by a lack of a model system. To address this, we engineered betalain-producing Nicotiana tabacum, by the introduction of three betalain biosynthetic genes. The plants were violet-red due to the accumulation of three betacyanins: betanin, isobetanin, and betanidin. Under salt stress, betacyanic seedlings had increased survivability and leaves of mature plants had higher photochemical quantum yields of photosystem II (F _v /F _m ) and faster photosynthetic recovery after saturating light treatment. Under salt stress, compared to controls betacyanic leaf disks had no loss of carotenoids, a slower rate of chlorophyll degradation, and higher F _v /F _m values. Furthermore, simulation of betacyanin pigmentation by using a red filter cover improved F _v /F _m value of green tissue under salt stress. Our results confirm a direct causal role of betacyanins in plant salinity tolerance and indicate a key mechanism is photoprotection. A role in delaying leaf senescence was also indicated, and the enhanced antioxidant capability of the betacyanic leaves suggested a potential contribution to scavenging reactive oxygen species. The study can inform the development of novel biotechnological approaches to improving agricultural productivity in saline-affected areas.

Assessment of hyperspectral indicators related to the content of phenolic compounds and multispectral fluorescence records in chicory leaves exposed to various light environments

Hyperspectral analysis represents a powerful technique for diagnostics of morphological and chemical information from aboveground parts of the plants, but the real potential of the method in pre-screening of phenolics in leaves is still insufficiently explored. In this study, assessment of the sensitivity and reliability of non-invasive methods of various phenolic compounds, also analyzed by HPLC in chicory plants (Cichorium intybus L.) exposed to various color light pretreatments was done. The hyperspectral records in visible and near infrared (VNIR) spectra were recorded using a handheld spectrometer and relationships between the specific hyperspectral parameters and the contents of tested phenolic compounds in chicory leaves were analyzed. Moreover, the correlations between the hyperspectral parameters and related parameters derived from the multispectral fluorescence records were assessed to compare the sensitivity of both techniques. The results indicated a relatively high correlation of anthocyanin-related parameters (ARI, mARI, mACI indices) with the content of some of tested phenolic compounds (quercetin-3-gluconuride, isorhamnetine-3-gluconuride, etc.), as well as with fluorescence ANTH index. Similar trends were observed in flavonoid parameter based on the near infra-red spectral bands (700, 760 nm), which expressed a high correlation with chlorogenic acid. On the other hand, the most frequently used flavonoid (FLAVI) indices based on UV-to-blue band reflectance showed very weak correlations with phenolic compounds, as well as with fluorescence FLAV index. The detailed analysis of the correlation between reflectance and fluorescence flavonoid parameters has shown that the parameters based on spectral reflectance are sensitive to increase of UV-absorbing compounds from low to moderate values, but, unlike the fluorescence parameter, they are not useful to recognize a further increase from middle to high or very high contents. Thus, our results outlined the possibilities, but also the limits of the use of hyperspectral analysis for rapid screening phenolic content, providing a practical evidence towards more efficient production of bioactive compounds for pharmaceutical or nutraceutical use.

Response of Scenedesmus quadricauda (Chlorophyceae) to Salt Stress Considering Nutrient Enrichment and Intracellular Proline Accumulation

Aquatic organisms are exposed to a wide range of salinity, which could critically affect their survival and growth. However, their survival and growth response to salinity stress remain unclear. This study evaluates the growth response and intracellular proline accumulation of green algae, Scenedesmus quadricauda, isolated from brackish water, against dissolved salts stress with N and P enrichment. We tested a hypothesis that nutrient enrichment can relieve the dissolved salts stress of algae by accumulating intracellular proline, thereby improving survival and growth. Four levels of salinity (0, 3, 6, 12 psu) were experimentally manipulated with four levels of nutrient stoichiometry (N:P ratio = 2, 5, 10, 20) at constant N (1 mgN/L) or P levels (0.05 and 0.5 mgP/L). In each set of experiments, growth rate and intracellular proline content were measured in triplicate. The highest level of salinity inhibited the growth rate of S. quadricauda, regardless of the nutrient levels. However, with nutrient enrichment, the alga showed tolerance to dissolved salts, reflecting intracellular proline synthesis. Proline accumulation was most prominent at the highest salinity level, and its maximum value appeared at the highest N:P ratio (i.e., highest N level) in all salinity treatments, regardless of P levels. Therefore, the effects of P and N on algal response to salt stress differ.

Physiological and iTRAQ-based proteomic analyses reveal the function of exogenous γ-aminobutyric acid (GABA) in improving tea plant (Camellia sinensis L.) tolerance at cold temperature

BACKGROUND

Internal γ-Aminobutyric Acid (GABA) interacting with stress response substances may be involved in the regulation of differentially abundant proteins (DAPs) associated with optimum temperature and cold stress in tea plants (Camellia sinensis (L.) O. Kuntze).

RESULTS

Tea plants supplied with or without 5.0 mM GABA were subjected to optimum or cold temperatures in this study. The increased GABA level induced by exogenous GABA altered levels of stress response substances - such as glutamate, polyamines and anthocyanins - in association with improved cold tolerance. Isobaric tags for relative and absolute quantification (iTRAQ) - based DAPs were found for protein metabolism and nucleotide metabolism, energy, amino acid transport and metabolism other biological processes, inorganic ion transport and metabolism, lipid metabolism, carbohydrate transport and metabolism, biosynthesis of secondary metabolites, antioxidant and stress defense.

CONCLUSIONS

The iTRAQ analysis could explain the GABA-induced physiological effects associated with cold tolerance in tea plants. Analysis of functional protein-protein networks further showed that alteration of endogenous GABA and stress response substances induced interactions among photosynthesis, amino acid biosynthesis, and carbon and nitrogen metabolism, and the corresponding differences could contribute to improved cold tolerance of tea plants.

Bioactive Phytochemicals and Antioxidant Properties of the Grains and Sprouts of Colored Wheat Genotypes

The grains and sprouts of colored wheat genotypes (having blue, purple and yellow colored grains) contain specific anthocyanidins, such as pelargonidin and cyanidin derivatives, that produce beneficial health effects. The objective of the presented study is to compare the antioxidant capacity and contents of bioactive phytochemicals in grains and sprouts of wheat genotypes that differ in grain color. The methods α, α-diphenyl-β-picrylhydrazyl (DPPH) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) scavenging activities, together with spectrophotometrical and high-performance thin-layer chromatography (HPTLC) methods, were used to study the presence of total phenolics, flavonoids, anthocyanins and anthocyanidins (pelargonidin, peonidin, cyanidin, delphinidin) content. It was predicted that the sprouts of all colored wheat genotypes would have significantly higher total flavonoids, total phenolics, anthocyanidin levels and antioxidant activity than the grains. The correlation results between antioxidant activity and contents of bioactive phytochemicals in grains and sprouts of colored wheat genotypes have shown a high correlation for cyanidin and pelargonidin, especially in grains, as well as quercetin in sprouts. It was found that total anthocyanin, quercetin and pelargonidin contents were significantly higher in the sprouts of the purple wheat genotypes than in the blue or yellow wheat genotypes. Delphinidin was detected at a higher level in the grains than in the sprouts of the blue wheat genotypes. Peonidin was present at very low quantities in the grains of all colored wheat genotypes. The sprouts of the purple wheat genotypes, among the colored wheat genotypes, had the highest pelargonidin, cyanidin and quercetin contents and, therefore, can be a promising source for functional food use.