Profile of phenolic compounds and antioxidant activity of organically and conventionally grown black-grain barley genotypes treated with biostimulant

Beneficial dietary and pro-health values, have resulted in the increasing consumption importance of barley. Therefore, genotypes and cultivation methods are sought that guarantee high functional value of grain. The aim of the study was to assess the content of phenolic acids, flavonoids, chlorophylls, anthocyanidins, phytomelanin and antioxidant activity of grain of three barley genotypes depending on agricultural technology. Two of them are primary genotypes with dark grain pigmentation Hordeum vulgare L. var nigricans and H. vulgare L. var. rimpaui, the third is a modern cultivar 'Soldo' H. vulgare with yellow grain, which is the control sample. Evaluated the effect of foliar application of a amino-acids biostimulant on the functional properties of grain under the conditions of organically and conventionally cultivations. The results indicated a higher antioxidant activity and the concentration of phenolic acids, flavonoids and phytomelanin in the black-grain genotypes. Organic cultivation and application of amino acids had increased the content of phenolic compounds in grain. The antioxidant activity was correlated with the content of syringic acid, naringenin, quercetin, luteolin and phytomelanin. Organically cultivation and the foliar application of an amino acid biostimulant improved the functional properties of barley grain, in particular the original, black-grained genotypes.

Exogenous Melatonin Enhances the Low Phosphorus Tolerance of Barley Roots of Different Genotypes

Melatonin (N-acetyl-5-methoxytryptamine) plays an important role in plant growth and development, and in the response to various abiotic stresses. However, its role in the responses of barley to low phosphorus (LP) stress remains largely unknown. In the present study, we investigated the root phenotypes and metabolic patterns of LP-tolerant (GN121) and LP-sensitive (GN42) barley genotypes under normal P, LP, and LP with exogenous melatonin (30 μM) conditions. We found that melatonin improved barley tolerance to LP mainly by increasing root length. Untargeted metabolomic analysis showed that metabolites such as carboxylic acids and derivatives, fatty acyls, organooxygen compounds, benzene and substituted derivatives were involved in the LP stress response of barley roots, while melatonin mainly regulated indoles and derivatives, organooxygen compounds, and glycerophospholipids to alleviate LP stress. Interestingly, exogenous melatonin showed different metabolic patterns in different genotypes of barley in response to LP stress. In GN42, exogenous melatonin mainly promotes hormone-mediated root growth and increases antioxidant capacity to cope with LP damage, while in GN121, it mainly promotes the P remobilization to supplement phosphate in roots. Our study revealed the protective mechanisms of exogenous MT in alleviating LP stress of different genotypes of barley, which can be used in the production of phosphorus-deficient crops.

The antioxidant defense responses of Hordeum vulgare L. to polycyclic aromatic hydrocarbons and their derivatives in biochar-amended soil

The recent studies indicated that the biochar (BC) may be a source of polycyclic aromatic hydrocarbons (PAHs) as well as their oxygen, nitrogen, or sulfur-containing derivatives that are considered as more toxic pollutants than their parent compounds. Here, the assessment of the impact of various biochars addition (1% wt.) to soil on barley Hordeum vulgare L. growth was presented. The concentrations of bioavailable PAHs and their derivatives in biochar were determined. PAHs increased reactive oxygen species generation resulting in oxidative stress in organisms. In this study, the response of soil-grown plants was examined in terms of the activity of the antioxidative enzymes (superoxide dismutase, catalase, peroxidase), lipid peroxidation, and the expression of genes related to oxidative stress. The results indicate that despite low content of a bioavailable fraction of parent compounds and their derivatives (up to 4.45 ± 0.24 ng g_biochar^-1 and 0.83 ± 0.03 ng L^-1, respectively) the biochemical response of plant was present, the activity of superoxide dismutase increased up to 2 times, but the activity of the other enzymes was lowered. The transcript level values support the studies on enzymatic activity. The presence of PAHs and their derivatives induced oxidative stress slightly but the plant was able to mitigate it.

Physiological and Epigenetic Reaction of Barley (Hordeum vulgare L.) to the Foliar Application of Silicon under Soil Salinity Conditions

Soil salinity is an important environmental factor affecting physiological processes in plants. It is possible to limit the negative effects of salt through the exogenous application of microelements. Silicon (Si) is widely recognized as an element improving plant resistance to abiotic and biotic stresses. The aim of the research was to determine the impact of foliar application of Si on the photosynthetic apparatus, gas exchange and DNA methylation of barley (Hordeum vulgare L.) grown under salt stress. Plants grown under controlled pot experiment were exposed to sodium chloride (NaCl) in the soil at a concentration of 200 mM, and two foliar applications of Si were made at three concentrations (0.05%, 0.1% and 0.2%). Measurements were made of relative chlorophyll content in leaves (CCl), gas exchange parameters (C_i, E, g_s, and P_N), and selected chlorophyll fluorescence parameters (F_v/F_m, F_v/F₀, PI and RC/ABS). Additionally, DNA methylation level based on cytosine methylation within the 3′CCGG 5′ sequence was analyzed. Salinity had a negative effect on the values of the parameters examined. Exogenous application of Si by spraying leaves increased the values of the measured parameters in plants. Plants treated with NaCl in combination with the moderate (0.1%) and highest (0.2%) dose of Si indicated the lowest methylation level. Decrease of methylation implicated with activation of gene expression resulted in better physiological parameters observed in this group of barley plants.

Early gene expression response of barley root tip to toxic concentrations of cadmium

Already a short-term Cd treatment induces changes in gene expression in barley root tips via IAA and ROS signaling during mild and severe Cd stress, respectively. Even a short, 30 min, Cd treatment of roots induced a considerable alteration in gene expression in the barley root tips within an hour after the treatments. The very early activation of MYB1 transcription factor expression is partially regulated by auxin signaling in mildly stressed seedlings. An increase in allene oxide cyclase and NADPH oxidase expression was a distinguishing feature of root tips response to mild Cd stress and their expression is activated via IAA signaling. Meanwhile, early changes in the level of dehydrin transcripts were detected in moderately and severely stressed root tips, and their induction is related to altered ROS homeostasis in cells. The early activation of glutathione peroxidase expression by mild Cd stress indicates the involvement of IAA in the signaling process. In contrast, early ascorbate peroxidase expression was induced only with Cd treatment causing severe stress and ROS play central roles in its induction. The expression of cysteine protease was activated similarly in both mildly and severely Cd-stressed roots; consequently, both increased IAA and ROS levels take part in the regulation of cysteine protease expression. The Cd-evoked accumulation of BAX Inhibitor-1 mRNA was characteristic for moderately and severely stressed roots. Whereas decreased IAA level did not affect its expression, rotenone-mediated ROS depletion markedly reduced the Cd-induced expression of BAX Inhibitor-1. An early increase of alternative oxidase levels in the root tip cells indicated that the reduction of mitochondrial superoxide generation is an important component of barley root response to severe Cd stress.

Mechanistic Insights into Potassium-Conferred Drought Stress Tolerance in Cultivated and Tibetan Wild Barley: Differential Osmoregulation, Nutrient Retention, Secondary Metabolism and Antioxidative Defense Capacity

Keeping the significance of potassium (K) nutrition in focus, this study explores the genotypic responses of two wild Tibetan barley genotypes (drought tolerant XZ5 and drought sensitive XZ54) and one drought tolerant barley cv. Tadmor, under the exposure of polyethylene glycol-induced drought stress. The results revealed that drought and K deprivation attenuated overall plant growth in all the tested genotypes; however, XZ5 was least affected due to its ability to retain K in its tissues which could be attributed to the smallest reductions of photosynthetic parameters, relative chlorophyll contents and the lowest Na⁺/K⁺ ratios in all treatments. Our results also indicate that higher H⁺/K⁺-ATPase activity (enhancement of 1.6 and 1.3-fold for shoot; 1.4 and 2.5-fold for root), higher shoot K⁺ (2 and 2.3-fold) and Ca²⁺ content (1.5 and 1.7-fold), better maintenance of turgor pressure by osmolyte accumulation and enhanced antioxidative performance to scavenge ROS, ultimately suppress lipid peroxidation (in shoots: 4% and 35%; in roots 4% and 20% less) and bestow higher tolerance to XZ5 against drought stress in comparison with Tadmor and XZ54, respectively. Conclusively, this study adds further evidence to support the concept that Tibetan wild barley genotypes that utilize K efficiently could serve as a valuable genetic resource for the provision of genes for improved K metabolism in addition to those for combating drought stress, thereby enabling the development of elite barley lines better tolerant of abiotic stresses.

Association of Barley Root Elongation with ABA-Dependent Transport of Cytokinins from Roots and Shoots under Supra-Optimal Concentrations of Nitrates and Phosphates

Changes in root elongation are important for the acquisition of mineral nutrients by plants. Plant hormones, cytokinins, and abscisic acid (ABA) and their interaction are important for the control of root elongation under changes in the availability of ions. However, their role in growth responses to supra-optimal concentrations of nitrates and phosphates has not been sufficiently studied and was addressed in the present research. Effects of supra-optimal concentrations of these ions on root elongation and distribution of cytokinins between roots and shoots were studied in ABA-deficient barley mutant Az34 and its parental variety, Steptoe. Cytokinin concentration in the cells of the growing root tips was analyzed with the help of an immunohistochemical technique. Increased concentrations of nitrates and phosphates led to the accumulation of ABA and cytokinins in the root tips, accompanied by a decline in shoot cytokinin content and inhibition of root elongation in Steptoe. Neither of the effects were detected in Az34, suggesting the importance of the ability of plants to accumulate ABA for the control of these responses. Since cytokinins are known to inhibit root elongation, the effect of supra-optimal concentration of nitrates and phosphates on root growth is likely to be due to the accumulation of cytokinins brought about by ABA-induced inhibition of cytokinin transport from roots to shoots.

Effect of diclofenac and naproxen and their mixture on spring barley seedlings and Heterocypris incongruens

Nonsteroidal anti-inflammatory drugs (NSAIDs) are a popular group of drugs used worldwide. These drugs are also available over the counter, which implies that their consumption is not strictly regulated. They are released through wastewater and feces and can have adverse effects on the environment. The present study aimed to evaluate the effect of two NSAIDs, diclofenac (DCF) and naproxen (NAP), and their mixture (DCF + NAP) on spring barley seedlings and ostracods Heterocypris incongruens. The tested drugs had a negative impact on bivalve ostracods and the studied plants. DCF was the most toxic toward ostracods, while spring barley seedlings were affected the most by NAP. The application of the tested compounds and their mixture resulted in a decrease in fresh weight yield and the content of photosynthetic pigments. In addition, an increase in H₂O₂ and proline content and changes in the activity of antioxidant enzymes (POD, APX, CAT, and SOD) were observed.

Androgenic-Induced Transposable Elements Dependent Sequence Variation in Barley

A plant genome usually encompasses different families of transposable elements (TEs) that may constitute up to 85% of nuclear DNA. Under stressful conditions, some of them may activate, leading to sequence variation. In vitro plant regeneration may induce either phenotypic or genetic and epigenetic changes. While DNA methylation alternations might be related, i.e., to the Yang cycle problems, DNA pattern changes, especially DNA demethylation, may activate TEs that could result in point mutations in DNA sequence changes. Thus, TEs have the highest input into sequence variation (SV). A set of barley regenerants were derived via in vitro anther culture. High Performance Liquid Chromatography (RP-HPLC), used to study the global DNA methylation of donor plants and their regenerants, showed that the level of DNA methylation increased in regenerants by 1.45% compared to the donors. The Methyl-Sensitive Transposon Display (MSTD) based on methylation-sensitive Amplified Fragment Length Polymorphism (metAFLP) approach demonstrated that, depending on the selected elements belonging to the TEs family analyzed, varying levels of sequence variation were evaluated. DNA sequence contexts may have a different impact on SV generated by distinct mobile elements belonged to various TE families. Based on the presented study, some of the selected mobile elements contribute differently to TE-related SV. The surrounding context of the TEs DNA sequence is possibly important here, and the study explained some part of SV related to those contexts.

Assessing the toxicity and accumulation of bulk- and nano-CuO in Hordeum sativum L

The effects of bulk- and nano-CuO were monitored on barley (Hordeum sativum L.) in hydroponic conditions. The anatomical and cyto-/morphometric parameters of plants, exposed to both types of CuO in different doses (300 and 2000 mg/L) were recorded. The germination rate, root and shoot lengths decreased in a dose-dependent manner. Exposure to nano-CuO significantly increased Cu content in the H. sativum roots; however, the translocation rates of dissolved Cu were low and showed less accumulation in above-ground tissues. The differences between nano- and bulk-CuO treated plants were sufficiently evident, but at lower concentrations, these differences were non-significant. The relative seed germination inhibition was noted up to 11% and 22% under the high dose of bulk- and nano-CuO, respectively; however, at low dose, it was non-significant. The relative root length was reduced 3.6 fold by bulk- and 1.5 fold by nano-CuO, and shoot lengths decreased 1.6 fold by bulk- and 1.4 fold by nano-CuO under the high dose after growth of 30 days. It indicated more morphological effects on H. sativum caused by bulk- than the nano-CuO. The cytomorphometric analysis indicated the average cortex cell, total cortex, and total central cylinder areas of root cells and the average areas of chlorenchyma leaf cells were increased as compared to control in both bulk- and nano-CuO treated plants. It showed destructive effects of nano- and bulk-CuO on cellular organizations of H. sativum anatomy. Thus, at the low dose, the minimal effects of nano-CuO were observed than the bulk. Therefore, the finding could be interest for the safe application of nano-CuO.

Abscisic acid mediates barley rhizosheath formation under mild soil drying by promoting root hair growth and auxin response

Soil drying enhances root ABA accumulation and rhizosheath formation, but whether ABA mediates rhizosheath formation is unclear. Here, we used the ABA-deficient mutant Az34 to investigate molecular and morphological changes by which ABA could affect rhizosheath formation. Mild soil drying with intermittent watering increased rhizosheath formation by promoting root and root hair elongation. Attenuated root ABA accumulation in Az34 barley constrained the promotion of root length and root hair length by drying soil, such that Az34 had a smaller rhizosheath. Pharmacological experiments of adding fluridone (an ABA biosynthesis inhibitor) and ABA to drying soil restricted and enhanced rhizosheath formation respectively in Az34 and wild-type Steptoe barley. RNA sequencing suggested that ABA accumulation mediates auxin synthesis and responses and root and root hair elongation in drying soil. In addition, adding indole-3-acetic acid (IAA) to drying soil increased rhizosheath formation by promoting root and root hair elongation in Steptoe and Az34 barley. Together, these results show that ABA accumulation induced by mild soil drying enhance barley rhizosheath formation, which may be achieved through promoting auxin response.

Effects of benzo[a]pyrene toxicity on morphology and ultrastructure of Hordeum sativum

Many studies have been devoted to investigation of toxic benzo(a)pyrene (BaP) compound, but studies involving changes at the cellular level are insufficient to understand the mechanisms of polycyclic aromatic hydrocarbons (PAHs) effect on plants. To study the toxicity of BaP, a model vegetation experiment was conducted on cultivation of spring barley (Hordeum sativum distichum) on artificially polluted BaP soil at different concentrations. The article discusses the intake of BaP from the soil into the plant and its effect on the organismic and cellular levels of plant organization. The BaP content in the organs of spring barley was determined by the method of saponification. With an increase in the concentration of BaP in the soil, its content in plants also rises, which leads to inhibition of growth processes. The BaP content in the green part of Hordeum sativum increased from 0.3 µg kg^-1 in control soil up to 2.6 µg kg^-1 and 16.8 µg kg^-1 under 20 and 400 ng/g BaP applying in soil, as well as in roots: 0.9 µg kg^-1, 7.7 µg kg^-1, 42.8 µg kg^-1, respectively. Using light and electron microscopy, changes in the tissues and cells of plants were found and it was established that accumulation of BaP in plant tissues caused varying degrees of ultrastructural damage depending on the concentration of pollutant. BaP had the greatest effect on the root, significant changes were found in it both at histological and cytological levels, while changes in the leaves were observed only at the cytological level. The results provide significant information about the mechanism of action of BaP on agricultural plants.

The toxic effect of CuO of different dispersion degrees on the structure and ultrastructure of spring barley cells (Hordeum sativum distichum)

Nowadays, nanotechnology is one of the most dynamically developing and most promising technologies. However, the safety issues of using metal nanoparticles, their environmental impact on soil and plants are poorly understood. These studies are especially important in terms of copper-based nanomaterials because they are widely used in agriculture. Concerning that, it is important to study the mechanism behind the mode of CuO nanoparticles action at the ultrastructural intracellular level. It is established that the contamination with CuO has had a negative influence on the development of spring barley. A greater toxic effect has been exerted by the introduction of CuO nanoparticles as compared to the macrodispersed form. A comparative analysis of the toxic effects of copper oxides and nano-oxides on plants has shown changes in the tissue and intracellular levels in the barley roots. However, qualitative changes in plant leaves have not practically been observed. In general, conclusions can be made that copper oxide in nano-dispersed form penetrates better from the soil into the plant and can accumulate in large quantities in it.

The Effects of Cold Atmospheric Pressure Plasma on Germination Parameters, Enzyme Activities and Induction of DNA Damage in Barley

Climate change, environmental pollution and pathogen resistance to available chemical agents are part of the problems that the food industry has to face in order to ensure healthy food for people and livestock. One of the promising solutions to these problems is the use of cold atmospheric pressure plasma (CAPP). Plasma is suitable for efficient surface decontamination of seeds and food products, germination enhancement and obtaining higher yields in agricultural production. However, the plasma effects vary due to plasma source, treatment conditions and seed type. In our study, we tried to find the proper conditions for treatment of barley grains by diffuse coplanar surface barrier discharge, in which positive effects of CAPP, such as enhanced germination or decontamination effects, would be maximized and harmful effects, such as oxidation and genotoxic potential, minimized. Besides germination parameters, we evaluated DNA damage and activities of various germination and antioxidant enzymes in barley seedlings. Plasma exposure resulted in changes in germination parameters and enzyme activities. Longer exposures had also genotoxic effects. As such, our findings indicate that appropriate plasma exposure conditions need to be carefully optimized in order to preserve germination, oxidation balance and genome stability, should CAPP be used in agricultural practice.

Nicotinamide Mononucleotide Potentiates Resistance to Biotrophic Invasion of Fungal Pathogens in Barley

Nicotinamide mononucleotide (NMN), a precursor of nicotinamide adenine dinucleotide (NAD), induces disease resistance to the Fusarium head blight fungus Fusarium graminearum in Arabidopsis and barley, but it is unknown at which stage of the infection it acts. Since the rate of haustorial formation of an obligate biotrophic barley powdery mildew fungus Blumeria graminis f. sp. hordei (Bgh) was significantly reduced in NMN-treated coleoptile epidermal cells, the possibility that NMN induces resistance to the biotrophic stage of F. graminearum was investigated. The results show that NMN treatment caused the wandering of hyphal growth and suppressed the formation of appressoria-like structures. Furthermore, we developed an experimental system to monitor the early stage of infection in real-time and analyzed the infection behavior. We observed that the hyphae elongated windingly by NMN treatment. These results suggest that NMN potentiates resistance to the biotrophic invasion of F. graminearum as well as Bgh.

Effect of Fe3O4 and CuO Nanoparticles on Morphology, Genotoxicity, and miRNA Expression on Different Barley (Hordeum vulgare L.) Genotypes

Metal nanoparticles (NPs) have an influence on plant growth and development. They can alter plant shoot and root length, fresh biomass production, and even influence the genome. Nanoparticles are also able to affect expression levels of plant microRNAs. MicroRNAs are able to protect plants from biotic stress, including pathogens which cause powdery mildew. In this study, Hordeum vulgare L. varieties "Marthe" and "KWS Olof" were grown in hydroponics with magnetic iron oxide (Fe3O4) and copper oxide (CuO) NPs added at 17, 35, and 70 mg/L. Plant morphology, genotoxicity, and expression of miR156a were investigated. The Fe3O4 and CuO NPs demonstrated different effects on the barley varieties, namely, Fe3O4 nanoparticles increased plant shoot and root lengths and fresh biomass, while CuO nanoparticles decreased them. CuO NPs presence caused larger changes on barley genome compared to Fe3O4 NPs. Thus, Fe3O4 NPs reduced genome stability to 72% in the "Marthe" variety and to 76.34% in the "KWS Olof" variety, while CuO NPs reduced genome stability to 53.33% in "Marthe" variety and in the "KWS Olof" variety to 68.81%. The miR156a expression levels after Fe3O4 NPs treatment did not change in the "Marthe" variety, but increased in the "KWS Olof" variety, while CuO NPs treatment increased miRNA expression levels in the "Marthe" variety but decrease them in the "KWS Olof" variety. As NPs are able to influence miRNA expression and miRNAs can affect the plant resistance, obtained results suggest that tested NPs may alter plant resistance response to pathogens.

Transcriptome analysis reveals the tolerant mechanisms to cobalt and copper in barley

Cobalt (Co) and copper (Cu) co-exist commonly in the contaminated soils and at excessive levels, they are toxic to plants. However, their joint effect and possible interaction have not been fully addressed. In this work, a hydroponic experiment was performed to investigate the combined effects of Co and Cu on two barley genotypes at transcriptional level by RNA-seq analysis. The results identified 358 genes inclusively expressed in both genotypes under single and combined treatments of Co and Cu, with most of them being related to metal transport, stress response and transcription factor. The combined treatment induced more differently expressed genes (DEGs) than the single treatment, with Yan66, a metal tolerant genotype having more DEGs than Ea52, a sensitive genotype. The pathways associated with anthocyanin biosynthesis, MAPK signaling, glutathione biosynthesis, phenylalanine metabolism, photosynthesis, arginin biosynthesis, fatty acid elongation, and plant hormone signal transduction biosynthesis were induced and inhibited in Yan66 and Ea52, respectively. Furthermore, flavonoid biosynthesis was much more largely enhanced and accordingly more free flavonoid components (naringin, narirutin and neohesperidin) were accumulated in Yan66 than in Ea52. It may be suggested that high tolerance to both Co and Cu in Yan66 is attributed to its high gene regulatory ability.

La, Ce and Nd in the soil-plant system in a vegetation experiment with barley (Hordeum vulgare L.)

Rare earth elements (REEs) have received enormous attention in recent years. However, there are many gaps in the understanding of their behavior in the soil-plant system. The aim of this study is to investigate the behavior of three most common REEs (La, Ce, Nd) in the soil-plant system directly on soil samples using barley (Hordeum vulgare L.) in a vegetation experiment. We attribute the absence of significant changes in plant biomass and photosynthetic pigment content to the reduced availability of REEs in soil samples. The concentration of water-soluble forms of La, Ce and Nd didn't exceed 1 mg/kg, while the concentration of exchangeable forms varied and decreased in a row La > Ce > Nd. The transfer factor (TF) from soil to above-ground biomass was low for all three elements (<1). The stem-to-leaf TF increased with the increase in REEs concentration in soil. The concentration in plant material increased in the row Ce < Nd < La. REEs concentrations in barley leaves didn't exceed 1-3% of the corresponding element concentration in soil samples. REEs concentration in plant tissues is in close direct correlation with the REEs total concentration in soil, water-soluble and exchange forms. REEs concentration in barley leaves is 3-4 times higher than in the stems and for the group with extraneous concentration of 200 mg/kg for La, Ce and Nd was 6.20 ± 1.48, 2.10 ± 0.51, 6.90 ± 3.00 mg/kg, respectively. We show that there were no major changes in barley plants, but further study is needed of the relationship between the absorption of lanthanides by plants and the content of various forms of lanthanides in the soil.

Adaptation Strategies of Halophytic Barley Hordeum marinum ssp. marinum to High Salinity and Osmotic Stress

The adaptation strategies of halophytic seaside barley Hordeum marinum to high salinity and osmotic stress were investigated by nuclear magnetic resonance imaging, as well as ionomic, metabolomic, and transcriptomic approaches. When compared with cultivated barley, seaside barley exhibited a better plant growth rate, higher relative plant water content, lower osmotic pressure, and sustained photosynthetic activity under high salinity, but not under osmotic stress. As seaside barley is capable of controlling Na⁺ and Cl⁻ concentrations in leaves at high salinity, the roots appear to play the central role in salinity adaptation, ensured by the development of thinner and likely lignified roots, as well as fine-tuning of membrane transport for effective management of restriction of ion entry and sequestration, accumulation of osmolytes, and minimization of energy costs. By contrast, more resources and energy are required to overcome the consequences of osmotic stress, particularly the severity of reactive oxygen species production and nutritional disbalance which affect plant growth. Our results have identified specific mechanisms for adaptation to salinity in seaside barley which differ from those activated in response to osmotic stress. Increased knowledge around salt tolerance in halophytic wild relatives will provide a basis for improved breeding of salt-tolerant crops.

Al-Tolerant Barley Mutant hvatr.g Shows the ATR-Regulated DNA Damage Response to Maleic Acid Hydrazide

ATR, a DNA damage signaling kinase, is required for cell cycle checkpoint regulation and detecting DNA damage caused by genotoxic factors including Al³⁺ ions. We analyzed the function of the HvATR gene in response to chemical clastogen-maleic acid hydrazide (MH). For this purpose, the Al-tolerant barley TILLING mutant hvatr.g was used. We described the effects of MH on the nuclear genome of hvatr.g mutant and its WT parent cv. “Sebastian”, showing that the genotoxic effect measured by TUNEL test and frequency of cells with micronuclei was much stronger in hvatr.g than in WT. MH caused a significant decrease in the mitotic activity of root cells in both genotypes, however this effect was significantly stronger in “Sebastian”. The impact of MH on the roots cell cycle, analyzed using flow cytometry, showed no differences between the mutant and WT.

Effect of cadmium stress on certain physiological parameters, antioxidative enzyme activities and biophoton emission of leaves in barley (Hordeum vulgare L.) seedlings

Biophoton emission is a well-known phenomenon in living organisms, including plant species; however, the underlying mechanisms are not yet well elucidated. Nevertheless, non-invasive stress detection is of high importance when in plant production and plant research. Therefore, the aim of our work was to investigate, whether biophoton emission is suitable for the detection of cadmium stress in the early phase of stress evolution and to identify certain stress-related events that occur rapidly upon cadmium exposure of barley seedlings parallel to biophoton emission measurements. Changes of biophoton emission, chlorophyll content estimation index, ascorbate level, the activity of ascorbate- and guaiacol peroxidase enzymes and lipid oxidation were measured during seven days of cadmium treatment in barley (Hordeum vulgareL.) seedlings. The results indicate that the antioxidant enzyme system responded the most rapidly to the stress caused by cadmium and the lipid oxidation-related emission of photons was detected in cadmium-treated samples as early as one day after cadmium exposure. Furthermore, a concentration-dependent increase in biophoton emission signals indicating an increased rate of antioxidative enzymes and lipid oxidation was also possible to determine. Our work shows evidence that biophoton emission is suitable to identify the initial phase of cadmium stress effectively and non-invasively.

Heterologous microProtein expression identifies LITTLE NINJA, a dominant regulator of jasmonic acid signaling

MicroProteins are small, often single-domain proteins that are sequence-related to larger, often multidomain proteins. Here, we used a combination of comparative genomics and heterologous synthetic misexpression to isolate functional cereal microProtein regulators. Our approach identified LITTLE NINJA (LNJ), a microProtein that acts as a modulator of jasmonic acid (JA) signaling. Ectopic expression of LNJ in Arabidopsis resulted in stunted plants that resembled the decuple JAZ (jazD) mutant. In fact, comparing the transcriptomes of transgenic LNJ overexpressor plants and jazD revealed a large overlap of deregulated genes, suggesting that ectopic LNJ expression altered JA signaling. Transgenic Brachypodium plants with elevated LNJ expression levels showed deregulation of JA signaling as well and displayed reduced growth and enhanced production of side shoots (tiller). This tillering effect was transferable between grass species, and overexpression of LNJ in barley and rice caused similar traits. We used a clustered regularly interspaced short palindromic repeats (CRISPR) approach and created a LNJ-like protein in Arabidopsis by deleting parts of the coding sentence of the AFP2 gene that encodes a NINJA-domain protein. These afp2-crispr mutants were also stunted in size and resembled jazD Thus, similar genome-engineering approaches can be exploited as a future tool to create LNJ proteins and produce cereals with altered architectures.

High accumulation of phenolics and amino acids confers tolerance to the combined stress of cobalt and copper in barley (Hordeum vulagare)

Cobalt (Co) and copper (Cu) co-exist in the metal contaminated soils and cause the serious toxicity to crops, while their interactive effect on plant growth and development is still poorly understood. In this work, a hydroponic experiment was carried out to reveal the interactive effect of Co and Cu on photosynthesis and metabolite profiles of two barley genotypes differing in metal tolerance. The results showed that both single and combined treatments of Co and Cu caused a significant reduction in chlorophyll content and photosynthetic rate of the two barley (Hordeum vulgare) genotypes, with the effect being greater for the combined treatment and the sensitive genotype (Ea52) being more affected than the tolerant genotype (Yan66). Compared to Cu or Co treatment alone, the combined treatment significantly increased the levels of phenolic components, including cinnamic derivatives (caffeic, chlorogenic, ferullic, p-coumaric); benzoic derivatives (p-hydroxybenzoic, vanillic, syringic, sallicilic, protocatechuic acid) as well as free amino acids, with Yan66 having more accumulation than Ea52. Meanwhile, under the combined treatment, the phenylalanine ammonialyase-related gene (HvPAL) was highly regulated along with the genes involved in the synthesis of malate (HvMDH) and citrate (HvCSY), with Ya66 showing the higher expression of these genes than Ea52. It can be concluded that higher Cu and Co stress tolerance in Yan66 is attributed to more accumulation of the metabolites including phenolics and amino acids.

Dynamics of localised nitrogen supply and relevance for root growth of Vicia faba ('Fuego') and Hordeum vulgare ('Marthe') in soil

Root growth responds to local differences in N-form and concentration. This is known for artificial systems and assumed to be valid in soil. The purpose of this study is to challenge this assumption for soil mesocosms locally supplied with urea with and without nitrification inhibitor. Soil column experiments with Vicia faba ('Fuego') and Hordeum vulgare ('Marthe') were performed to investigate soil solution chemistry and root growth response of these two species with contrasting root architectures to the different N-supply simultaneously. Root growth was analysed over time and separately for the fertiliser layer and the areas above and below with X-ray CT (via region growing) and WinRHIZO. Additionally, NO3- and NH4+ in soil and soil solution were analysed. In Vicia faba, no pronounced differences were observed, although CT analysis indicated different root soil exploration for high NH4+. In Hordeum vulgare, high NO3- inhibited lateral root growth while high NH4+ stimulated the formation of first order laterals. The growth response to locally distributed N-forms in soil is species specific and less pronounced than in artificial systems. The combination of soil solution studies and non-invasive imaging of root growth can substantially improve the mechanistic understanding of root responses to different N-forms in soil.

Indole-3-butyric acid priming reduced cadmium toxicity in barley root tip via NO generation and enhanced glutathione peroxidase activity

Activation of GPX and enhanced NO level play a key role in IBA-mediated enhanced Cd tolerance in young barley roots. Application of exogenous indole-3-acetic acid (IAA) or an IAA precursor improves the tolerance of plants to heavy metals. However, the physiology of these tolerance mechanisms remains largely unknown. Therefore, we studied the priming effect of indole-3-butyric acid (IBA), an IAA precursor, on mild and severe cadmium (Cd) stress-induced responses in roots of young barley seedlings. IBA, similarly to mild Cd stress, significantly increased the glutathione peroxidase (GPX) activity in the apexes of barley roots, which remained elevated after the IBA pretreatment as well. IBA pretreatment-evoked high nitric oxide generation in roots effectively reduced the high superoxide level under the severe Cd stress, leading to less toxic peroxynitrite accumulation accompanied by markedly reduced Cd-induced cell death. On the other hand, the IBA-evoked changes in IAA homeostasis resulted in root growth reorientation from longitudinal elongation to radial swelling. However, the application of an IAA signaling inhibitor, following the activation of defense responses by IBA, was able to promote root growth even at high concentrations of Cd. Based on the results, it can be concluded that the application of IBA, as an effective activator of Cd tolerance mechanisms in young barley roots, and the subsequent use of an IAA signaling inhibitor for the inhibition of root morphogenic responses induced by altered auxin metabolism, results in a high degree of root Cd tolerance, helping it to withstand even the transient exposure to lethal Cd concentration without the absolute inhibition of root growth.

Barley strigolactone signalling mutant hvd14.d reveals the role of strigolactones in abscisic acid-dependent response to drought

Strigolactones (SLs) are a group of plant hormones involved in many aspects of plant development and stress adaptation. Here, we investigated the drought response of a barley (Hordeum vulgare L.) mutant carrying a missense mutation in the gene encoding the SL-specific receptor HvD14. Our results clearly showed that hvd14.d mutant is hyper-sensitive to drought stress. This was illustrated by a lower leaf relative water content (RWC), impaired photosynthesis, disorganization of chloroplast structure, altered stomatal density and slower closure of stomata in response to drought in the mutant compared to the wild type parent cultivar Sebastian. Although the content of abscisic acid (ABA) and its derivatives remained unchanged in the mutant, significant differences in expression of genes related to ABA biosynthesis were observed. Moreover, hvd14.d was insensitive to ABA during seed germination. Analysis of Arabidopsis thaliana mutant atd14-1 also demonstrated that mutation in the SL receptor resulted in increased sensitivity to drought. Our results indicate that the drought-sensitive phenotype of barley SL mutant might be caused by a disturbed ABA metabolism and/or signalling pathways. These results together uncovered a link between SL signalling and ABA-dependent drought stress response in barley.

Synthesised magnetic nano-zeolite as a mycotoxins binder to reduce the toxicity of aflatoxins, zearalenone, ochratoxin A, and deoxynivalenol in barley

Agricultural commodities, particularly cereals can be contaminated with mycotoxins during the pre- and post-harvest stage. The main goal of this study was to evaluate the efficacy of magnetic zeolite nanocomposite (MZNC) as an adsorbent for the reduction of mycotoxins in barley flour. The MZNC is synthesised using an eco-friendly and efficient procedure and characterised by zeta potential, field emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The adsorbent amount that affects the adsorption capacity was optimised. Low amounts of the nanocomposite removed >99% of aflatoxins, 50% of ochratoxin A, 22% of zearalenone, and 1.8% of the deoxynivalenol from the contaminated sample and adsorption by MZNC was better than the natural zeolite; this phenomenon is related to the wide surface of nanocomposites. Results provide new insights into possible future research that could overcome the challenges of using nanotechnology to eliminate mycotoxins from agricultural products. It can be hoped that the presence of cheap and eco-friendly mycotoxin binders such as the MZNC that is synthesised and utilised in this research will help to produce secure food and feed products.

Timing-dependent effects of salicylic acid treatment on phytohormonal changes, ROS regulation, and antioxidant defense in salinized barley (Hordeum vulgare L.)

Cross-talk between exogenous salicylic acid (SA) and endogenous phytohormone pathways affects the antioxidant defense system and its response to salt stress. The study presented here investigated the effects of SA treatment before and during salt stress on the levels of endogenous plant growth regulators in three barley cultivars with different salinity tolerances: Hordeum vulgare L. cvs. Akhisar (sensitive), Erginel (moderate), and Kalaycı (tolerant). The cultivars' relative leaf water contents, growth parameters, proline contents, chlorophyll a/b ratios, and lipid peroxidation levels were measured, along with the activities of enzymes involved in detoxifying reactive oxygen species (ROS) including superoxide-dismutase, peroxidase, catalase, ascorbate-peroxidase, and glutathione-reductase. In addition, levels of several endogenous phytohormones (indole-3-acetic-acid, cytokinins, abscisic acid, jasmonic acid, and ethylene) were measured. Barley is known to be more salt tolerant than related plant species. Accordingly, none of the studied cultivars exhibited changes in membrane lipid peroxidation under salt stress. However, they responded differently to salt-stress with respect to their accumulation of phytohormones and antioxidant enzyme activity. The strongest and weakest increases in ABA and proline accumulation were observed in Kalaycı and Akhisar, respectively, suggesting that salt-stress was more effectively managed in Kalaycı. The effects of exogenous SA treatment depended on both the timing of the treatment and the cultivar to which it was applied. In general, however, where SA helped mitigate salt stress, it appeared to do so by increasing ROS scavenging capacity and antioxidant enzyme activity. SA treatment also induced changes in phytohormone levels, presumably as a consequence of SA-phytohormone salt-stress cross-talk.

Calmodulin HvCaM1 Negatively Regulates Salt Tolerance via Modulation of HvHKT1s and HvCAMTA4

Calcium (Ca2+) signaling modulates sodium (Na+) transport in plants; however, the role of the Ca2+ sensor calmodulin (CaM) in salt tolerance is elusive. We previously identified a salt-responsive calmodulin (HvCaM1) in a proteome study of barley (Hordeum vulgare) roots. Here, we employed bioinformatic, physiological, molecular, and biochemical approaches to determine the role of HvCaM1 in barley salt tolerance. CaM1s are highly conserved in green plants and probably originated from ancestors of green algae of the Chlamydomonadales order. HvCaM1 was mainly expressed in roots and was significantly up-regulated in response to long-term salt stress. Localization analyses revealed that HvCaM1 is an intracellular signaling protein that localizes to the root stele and vascular systems of barley. After treatment with 200 mm NaCl for 4 weeks, HvCaM1 knockdown (RNA interference) lines showed significantly larger biomass but lower Na+ concentration, xylem Na+ loading, and Na+ transportation rates in shoots compared with overexpression lines and wild-type plants. Thus, we propose that HvCaM1 is involved in regulating Na+ transport, probably via certain class I high-affinity potassium transporter (HvHKT1;5 and HvHKT1;1)-mediated Na+ translocation in roots. Moreover, we demonstrated that HvCaM1 interacted with a CaM-binding transcription activator (HvCAMTA4), which may be a critical factor in the regulation of HKT1s in barley. We conclude that HvCaM1 negatively regulates salt tolerance, probably via interaction with HvCAMTA4 to modulate the down-regulation of HvHKT1;5 and/or the up-regulation of HvHKT1;1 to reduce shoot Na+ accumulation under salt stress in barley.

Prediction of soil copper phytotoxicity to barley root elongation by an EDTA extraction method

Dose-response (toxicity) relationships explain how the response changes with exposure doses. However, the results of tests or observations are commonly based on total concentrations of contaminants in environments, not the exposure dose that causes toxicity. In the present study, the copper (Cu) phytotoxicity to barley root elongation was studied in 17 representative Chinese soils. Also, the EDTA-extractable Cu concentration was used to evaluate the extractability of Cu in soils. The results showed that the concentrations of EDTA-extractable Cu accounted for 89.6-91.2 % of total added Cu in soils and that soil pH, organic carbon content (OC) and cation exchange capacity (CEC) could explain over 85 % of the variance in Cu phytotoxicity thresholds based on EDTA-extractable concentration. The integrated relationship of EDTA-extractable Cu doses, toxicity, and soil properties was firstly derived quantitatively. The EDTA-extractable Cu plus soil properties can explain more than 90 % of the variance in the toxicity response of barley root elongation. The new integrated model based on dose-toxicity-soil properties will provide an approach for risk assessment of contaminated soils with different Cu sources to avoid the overestimation of the risk based on total Cu concentrations in soils, and to develop a reasonable remediation strategy for Cu contaminated soils.

Influence of Soil Properties and Aging on Antimony Toxicity for Barley Root Elongation

The study explored the Sb toxicity by investigating the impacts of 10% and 20% effective concentrations (EC10 and EC20, respectively) of Sb on the inhibition of barley root elongation in 21 Chinese soils with a wide range of physicochemical properties after aging for 3 months. The results demonstrated that various soil properties profoundly influenced the Sb toxicity which was ranged from 201-2506 mg Sb kg^-1 to 323-2973 mg Sb kg^-1 under EC10 and EC20, respectively. Soil sand fraction was a significant soil factor responsible for elevating Sb bioavailability. The bioavailable Sb concentration accounted for 2.08%-11.94% of total Sb content in all 21 soil samples and the decreased Sb bioavailability in this study was attributed to soil properties including soil clay fraction, amorphous and crystalloid iron, and oxides of manganese and aluminum. The findings would contribute in developing Sb toxicity threshold for establishing standard for Sb regulation in crop production.

Artificial intelligence models to predict acute phytotoxicity in petroleum contaminated soils

Environment pollutants, especially those from total petroleum hydrocarbons (TPH), have a highly complex chemical, biological and physical impact on soils. Here we study this influence via modelling the TPH acute phytotoxicity effects on eleven samples of soils from Sakhalin island in greenhouse conditions. The soils were contaminated with crude oil in different doses ranging from the 3.0-100.0 g kg^-1. Measuring the Hordeum vulgare root elongation, the crucial ecotoxicity parameter, we have estimated. We have also investigated the contrast effect in different soils. To predict TPH phytotoxicity different machine learning models were used, namely artificial neural network (ANN) and support vector machine (SVM). The models under discussion were proved to be valid using the mean absolute error method (MAE), the root mean square error method (RMSE), and the coefficient of determination (R²). We have shown that ANN and SVR can successfully predict barley response based on soil chemical properties (pH, LOI, N, P, K, clay, TPH). The best achieved accuracy was as following: MAE - 8.44, RMSE -11.05, and R² -0.80.

Genome-Wide Identification and Characterization of Drought Stress Responsive microRNAs in Tibetan Wild Barley

Drought stress is a major obstacle to agricultural production. Tibetan wild barley with rich genetic diversity is useful for drought-tolerant improvement of cereals. MicroRNAs (miRNAs) play critical roles in controlling gene expression in response to various environment perturbations in plants. However, the genome-wide expression profiles of miRNAs and their targets in response to drought stress are largely unknown in wild barley. In this study, a polyethylene glycol (PEG) induced drought stress hydroponic experiment was performed, and the expression profiles of miRNAs from the roots of two contrasting Tibetan wild barley genotypes XZ5 (drought-tolerant) and XZ54 (drought-sensitive), and one cultivated barley Tadmor (drought-tolerant) generated by high-throughput sequencing were compared. There were 69 conserved miRNAs and 1574 novel miRNAs in the dataset of three genotypes under control and drought conditions. Among them, seven conserved miRNAs and 36 novel miRNAs showed significantly genotype-specific expression patterns in response to drought stress. And 12 miRNAs were further regarded as drought tolerant associated miRNAs in XZ5, which mostly participate in gene expression, metabolism, signaling and transportation, suggesting that they and their target genes play important roles in plant drought tolerance. This is the first comparation study on the miRNA transcriptome in the roots of two Tibetan wild barley genotypes differing in drought tolerance and one drought tolerant cultivar in response to PEG treatment. Further results revealed the candidate drought tolerant miRNAs and target genes in the miRNA regulation mechanism in wild barley under drought stress. Our findings provide valuable understandings for the functional characterization of miRNAs in drought tolerance.

Combined QTL mapping and RNA-Seq profiling reveals candidate genes associated with cadmium tolerance in barley

The high toxicity of cadmium (Cd) and its ready uptake by plants has become a major agricultural problem. To investigate the genetic architecture and genetic regulation of Cd tolerance in barley, we conducted quantitative trait loci (QTL) analysis in the phenotypically polymorphic Oregon Wolfe Barley (OWB) mapping population, derived from a cross between Rec and Dom parental genotypes. Through evaluating the Cd tolerance of 87 available doubled haploid lines of the OWB mapping population at the seedling stage, one minor and one major QTL were detected on chromosomes 2H and 6H, respectively. For chlorosis and necrosis traits, the major QTL explained 47.24% and 38.59% of the phenotypic variance, respectively. RNA-Seq analysis of the parental seedlings under Cd treatment revealed 542 differentially expressed genes between Cd-tolerant Rec and Cd-susceptible Dom genotypes. By analyzing sequence variations in transcribed sequences of the parental genotypes, 155,654 SNPs and 1,525 InDels were identified between the two contrasting genotypes and may contribute to Cd tolerance. Finally, by integrating the data from the identified QTLs and RNA-Seq analysis, 16 Cd tolerance-related candidate genes were detected, nine of which were metal ion transporters. These results provide promising candidate genes for further gene cloning and improving Cd tolerance in barley.

Comparison Among Test Substrates in Metal Uptake and Toxicity to Folsomia candida and Hordeum vulgare

The main aim of this short review was to assess the effect of test medium on the bioavailability of metals to the soil invertebrate Folsomia candida and the barley plant Hordeum vulgare. Solution-only exposures and sand-solution media were suitable media with control survival of > 80%. Comparing toxicity and accumulation data, LC₅₀ and/or EC₅₀ values as well as internal concentrations of cadmium (Cd) and copper (Cu) were similar in the tests with different porewater composition for springtails and barley plants. Similar results for toxicity and bioaccumulation of Cd and Cu using different test substrates, suggest the importance of physiological handling of the effects by the organisms rather than the influence of test medium composition.

Comparative spatial lipidomics analysis reveals cellular lipid remodelling in different developmental zones of barley roots in response to salinity

Salinity-induced metabolic, ionic, and transcript modifications in plants have routinely been studied using whole plant tissues, which do not provide information on spatial tissue responses. The aim of this study was to assess the changes in the lipid profiles in a spatial manner and to quantify the changes in the elemental composition in roots of seedlings of four barley cultivars before and after a short-term salt stress. We used a combination of liquid chromatography-tandem mass spectrometry, inductively coupled plasma mass spectrometry, matrix-assisted laser desorption/ionization mass spectrometry imaging, and reverse transcription - quantitative real time polymerase chain reaction platforms to examine the molecular signatures of lipids, ions, and transcripts in three anatomically different seminal root tissues before and after salt stress. We found significant changes to the levels of major lipid classes including a decrease in the levels of lysoglycerophospholipids, ceramides, and hexosylceramides and an increase in the levels of glycerophospholipids, hydroxylated ceramides, and hexosylceramides. Our results revealed that modifications to lipid and transcript profiles in plant roots in response to a short-term salt stress may involve recycling of major lipid species, such as phosphatidylcholine, via resynthesis from glycerophosphocholine.

Specificity of Cd, Cu, and Fe effects on barley growth, metal contents in leaves and chloroplasts, and activities of photosystem I and photosystem II

Cd, Cu, and Fe were used to reveal the specificity of their toxic actions. We studied the effects of heavy metals on the growth of barley seedlings, contents of cations in leaves and chloroplasts, induced chlorophyll fluorescence and P₇₀₀ light absorption. Differences were found at each level of research. We measured the contents of Cd, Cu, Fe, Mn, Zn, Ca, Mg, and K. The proportion of cations in leaves targeted to chloroplasts varied from 0.1% (K) to >90% (Fe). Their levels changed in different ways. We found no correlation between changes in cation contents in leaves and chloroplasts. Treatment with Cd, Cu, and Fe increased the contents of some cations. The extra portions were targeted primarily out of chloroplasts, which was most noticeable in the case of Cu and Fe. Cd treatment decreased non-photochemical quenching with concomitant increases in closed photosystem II. We introduced new coefficients qC for closed photosystem II and X(II) to compare the yields of photosystem II and photosystem I. Cd likely decreased both PSI content in leaves and its quantum yield. In control plants, the quantum yield ratio of PSI/PSII increased gradually from 1.25 under low light to 4 under high light. Cd treatment prevented the increase under moderate light; under high light the ratio reached 2. Cu treatment increased the acceptor side limitation of photosystem I under low light; components of the Calvin cycle likely demand more light for activation in Cu-treated plants.

Thymol Chemotype Origanum vulgare L. Essential Oil as a Potential Selective Bio-Based Herbicide on Monocot Plant Species

Searching for new bio-based herbicides is crucial for decreasing chemical pollution, protecting the environment, and sustaining biodiversity. Origanum vulgare is considered a promising source of essential oil with herbicidal effect. The mode of action is not known. The present study focused on (1) comparison of phytotoxic activity of Origanum vulgare EO on monocot (Triticum aestivum and Hordeum vulgare) and dicot species (Lepidium sativum and Sinapis alba); (2) and evaluating other antimicrobial biological activities against phytopatogen bacteria (Clavibacter michiganensis, Pseudomonas syringae pv. phaseolicola, Pseudomonas savastanoi, and Xanthomonas campestris); antifungal activity against Monilinia fructicola, Aspergillus niger, Penicillium expansum, and Botrytis cinerea; cytotoxic activity and antioxidant activity. According to the GC/MS analyses, the EO belongs to the thymol chemotype O. vulgare with its high content of thymol (76%). Germination of all four species was not influenced by EO. The phytotoxic effect was statistically significant in the monocot species, while in the dicot species the opposite was observed-a stimulation effect, which was also statistically significant. Strong biological activity of O. vulgare EO was noted on all phytopatogen bacteria and fungi in the highest dose. Cytotoxic activity showed an IC₅₀ = 50.5 μg/mL. Antioxidant activity showed an IC₅₀ = 106.6 μg/mL after 45 min experimental time. Based on the presented results, it is possible to conclude that thymol chemotype O. vulgare essential oil could be potentially used as a herbicide with selective effects on monocot plant species.

Physiological and molecular mechanisms of cobalt and copper interaction in causing phyto-toxicity to two barley genotypes differing in Co tolerance

The combined effects of cobalt (Co) and copper (Cu) in their toxicity to plants is poorly studied although these two metals co-exist commonly in soil. In this study, a hydroponic experiment was carried out to investigate the effect of longer exposure of two barley genotypes differing in Co tolerance to the combined Co and Cu stress. The results confirmed the previous findings that Co accumulation in plant tissues was reduced by Cu presence, while Cu accumulation was stimulated by Co presence. Moreover, both single and combined treatments of Co and Cu reduced the mineral (Mn, Zn and K) uptake. Co and Cu applied alone or in combination at rate of 50 μM resulted in the significant reduction of plant growth and increase of oxidative stress (ROS and MDA), and meanwhile the capacity of scavenging active oxygen species (AOS) was enhanced, reflected by increased phytochelatin (PC) and glutathione (GSH and GSSG) content, as well as expression of the related genes (HvPCS1 and HvGR1). Yan66, a Co tolerant genotype was less affected in oxidative stress, and had higher AOS scavenging capacity in comparison with Ea52, a Co sensitive one. Among three HvSOD isoforms, only HvFeSOD expression was up-regulated in the combined treatment relative to control as well as the treatment of Co or Cu alone, while HvCuZnSOD and HvMnSOD were down-regulated and unaffected, respectively. In addition, the expressions of metal transporter genes (HvHMA2, HvHMA3 and HvHMA5) varied with genotype and metal treatments, with the extent being greater in Yan66 on the whole. The results suggest that upon longer exposure to the combined stress of Co and Cu, the greater phyto-toxicity than each element alone is associated with more Cu accumulation stimulated by Co and that, the higher regulation of transporter genes observed in Yan66 could in part explain for its higher metal tolerance ability.

MicroRNA-mediated responses to colchicine treatment in barley

In Hordeum vulgare, nine differentially expressed novel miRNAs were induced by colchicine. Five novel miRNA in colchicine solution showed the opposite expression patterns as those in water. Colchicine is a commonly used agent for plant chromosome set doubling. MicroRNA-mediated responses to colchicine treatment in plants have not been characterized. Here, we characterized new microRNAs induced by colchicine treatment in Hordeum vulgare using high-throughput sequencing. Our results showed that 39 differentially expressed miRNAs were affected by water treatment, including 34 novel miRNAs and 5 known miRNAs; 42 miRNAs, including 37 novel miRNAs and 5 known miRNAs, were synergistically affected by colchicine and water, and 9 differentially expressed novel miRNAs were induced by colchicine. The novel_mir69, novel_mir57, novel_mir75, novel_mir38, and novel_mir56 in colchicine treatment showed the opposite expression patterns as those in water. By analyzing these 9 differentially expressed novel miRNAs and their targets, we found that novel_mir69, novel_mir56 and novel_mir25 co-target the genes involving the DNA repair pathway. Based on our results, microRNA-target regulation network under colchicine treatment was proposed, which involves actin, cell cycle regulation, cell wall synthesis, and the regulation of oxidative stress. Overall, the results demonstrated the critical role of microRNAs mediated responses to colchicine treatment in plants.

Anatomical and ultrastructural responses of Hordeum sativum to the soil spiked by copper

Effects of Cu toxicity from contaminated soil were analysed in spring barley (Hordeum sativum distichum), a widely cultivated species in South Russia. In this study, H. sativum was planted outdoors in one of the most fertile soils-Haplic Chernozem spiked with high concentration of Cu and examined between the boot and head emergence phase of growth. Copper toxicity was observed to cause slow ontogenetic development of plants, changing their morphometric parameters (shape, size, colour). To the best of our knowledge, the ultrastructural changes in roots, stems and leaves of H. sativum induced by excess Cu were fully characterized for the first time using transmission electron microscopy. The plant roots were the most effected, showing degradation of the epidermis, reduced number of parenchyma cells, as well as a significant decrease in the diameter of the stele and a disruption and modification to its cell structure. The comparative analysis of the ultrastructure of control plants and plants exposed to the toxic effects of Cu has made it possible to reveal significant disruption of the integrity of the cell wall and cytoplasmic membranes in the root with deposition of electron-dense material. The changes in the ultrastructure of the main cytoplasmic organelles-endoplasmic reticulum, mitochondria, chloroplasts and peroxisomes-in the stem and leaves were found. The cellular Cu deposition, anatomical and ultrastructural modifications could mainly account for the primary impact points of metal toxicity. Therefore, this work extends the available knowledge of the mechanisms of the Cu effect tolerance of barley.

The HKT Transporter HvHKT1;5 Negatively Regulates Salt Tolerance

Maintaining low intracellular Na+ concentrations is an essential physiological strategy in salt stress tolerance in most cereal crops. Here, we characterized a member of the high-affinity K+ transporter (HKT) family in barley (Hordeum vulgare), HvHKT1;5, which negatively regulates salt tolerance and has different functions from its homology in other cereal crops. HvHKT1;5 encodes a plasma membrane protein localized to root stele cells, particularly in xylem parenchyma cells adjacent to the xylem vessels. Its expression was highly induced by salt stress. Heterogenous expression of HvHKT1;5 in Xenopus laevis oocytes showed that HvHKT1;5 was permeable to Na+, but not to K+, although its Na+ transport activity was inhibited by external K+ HvHKT1;5 knockdown barley lines showed improved salt tolerance, a dramatic decrease in Na+ translocation from roots to shoots, and increases in K+/Na+ when compared with wild-type plants under salt stress. The negative regulation of HvHKT1;5 in salt tolerance distinguishes it from other HKT1;5 members, indicating that barley has a distinct Na+ transport system. These findings provide a deeper understanding of the functions of HKT family members and the regulation of HvHKT1;5 in improving salt tolerance of barley.

Impact of calcium and magnesium substituted strontium nano-hexaferrite on mineral uptake, magnetic character, and physiology of barley (Hordeum vulgare L.)

In this study, calcium and magnesium substituted strontium nano-hexaferrites (Sr_0.96Mg_0.02Ca_0.02Fe₁₂O₁₉, SrMgCa nano-HF) were synthesized by the sol-gel auto-combustion method and their impact on the nutrient uptake, magnetic character and physiology of barley (Hordeum vulgare L.), a crop plant, was investigated. Structural, microstructural, and magnetic properties of nano-HF were evaluated by using vibrating sample magnetometry (VSM), X-ray diffraction (XRD), scanning electron microscopy (SEM) along with energy-dispersive X-ray (EDX) and elemental mapping techniques. Plants were hydroponically exposed to nano-HF (ranging from 125 to 1000 mg/L) for three weeks. Results showed that the SrMgCa nano-HF application enhanced germination rate (about 20%), tissue growth (about 38%), biomass (about 20%), soluble protein content (about 41%), and chlorophyll pigments (about 33-42%) when compared to the untreated control. In general, the plants showed the highest growth achievement at 125 or 250 mg/L of nano-HF treatment. However, higher doses diminished the growth parameters. Element concentrations and magnetic behavior analyses of plant parts proved that SrMgCa nano-HF with a size of 42.4 nm are up-taken by the plant roots and lead to increase in iron, calcium, magnesium, and strontium contents of leaves, which were about 20, 18, 3, and 60 times higher in 500 mg/L nano-HF-treated leaves than those of control, respectively. Overall, this study shows for the first time that the four elements have been internalized into the plant body through the application of substituted nano-HF. These findings suggest that mineral-substituted nanoparticles can be incorporated into plant breeding programs for the i) enhancement of seed germination and ii) treatment of plants by fighting with mineral deficiencies.

Drought stress and re-watering affect the abundance of TIP aquaporin transcripts in barley

Tonoplast Intrinsic Proteins (TIP) are plant aquaporins that are primarily localized in the tonoplast and play a role in the bidirectional flux of water and other substrates across a membrane. In barley, eleven members of the HvTIP gene subfamily have been identified. Here, we describe the transcription profile of the HvTIP genes in the leaves of barley seedlings being grown under optimal moisture conditions, drought stress and a re-watering phase. The applied drought stress caused a 55% decrease in the relative water content (RWC) in seedlings, while re-watering increased the RWC to 90% of the control. Our analysis showed that all HvTIP genes, except HvTIP3;2, HvTIP4;3 and HvTIP5.1, were expressed in leaves of ten-day-old barley seedlings under optimal water conditions with the transcripts of HvTIP2;3, HvTIP1;2 and HvTIP1;1 being the most abundant. We showed, for the first time in barley, a significant variation in the transcriptional activity between the analysed genes under drought stress. After drought treatment, five HvTIP genes, which are engaged in water transport, were down-regulated to varying degrees, while two, HvTIP3;1 and HvTIP4;1, were up-regulated. The HvTIP3;1 isoform, which is postulated as transporting hydrogen peroxide, expressed the highest increase of activity (ca. 5000x) under drought stress, thus indicating its importance in the response to this stress. Re-hydration caused the return of the expression of many genes to the level that was observed under optimal moisture conditions or, at least, a change in this direction Additionally, we examined the promotor regions of HvTIP and detected the presence of the cis-regulatory elements that are connected with the hormone and stress responses in all of the genes. Overall, our results suggest that 7 of 11 studied HvTIP (HvTIP1;1, HvTIP1;2, HvTIP2;1, HvTIP2;2, HvTIP2;3, HvTIP3;1, HvTIP4;1) have an important function during the adaptation of barley to drought stress conditions. We discuss the identified drought-responsive HvTIP in terms of their function in the adaptation of barley to this stress.

Biosynthesis of Phenylamide Phytoalexins in Pathogen-Infected Barley

Phytoalexins are inducible antimicrobial metabolites in plants, and have been indicated to be important for the rejection of microbial infection. HPLC analysis detected the induced accumulation of three compounds 1–3 in barley (Hordeum vulgare) roots infected by Fusarium culmorum, the causal agent of Fusarium root rot. Compounds 1–3 were identified as cinnamic acid amides of 9-hydroxy-8-oxotryptamine, 8-oxotryptamine, and (1H-indol-3-yl)methylamine, respectively, by spectroscopic analysis. Compounds 1 and 2 had been previously reported from wheat, whereas 3 was an undescribed compound. We named 1–3 as triticamides A–C, respectively, because they were isolated from barley and wheat, which belong to the Triticeae tribe. These compounds showed antimicrobial activities, indicating that triticamides function as phytoalexins in barley. The administration of deuterium-labeled N-cinnamoyl tryptamine (CinTry) to barley roots resulted in the effective incorporation of CinTry into 1 and 2, which suggested that they were synthesized through the oxidation of CinTry. Nine putative tryptamine hydroxycinnamoyl transferase (THT)-encoding genes (HvTHT1–HvTHT9) were identified by database search on the basis of homology to known THT gene sequences from rice. Since HvTHT7 and HvTHT8 had the same sequences except one base, we measured their expression levels in total by RT-qPCR. HvTHT7/8 were markedly upregulated in response to infection by F. culmorum. The HvTHT7 and HvTHT8 enzymes preferred cinnamoyl- and feruloyl-CoAs as acyl donors and tryptamine as an acyl acceptor, and (1H-indol-3-yl)methylamine was also accepted as an acyl acceptor. These findings suggested that HvTHT7/8 are responsible for the induced accumulation of triticamides in barley.

Low toxin doses change plant size distribution in dense populations - Glyphosate exposed Hordeum vulgare as a greenhouse case study

Numerous intentionally released toxins persist in agricultural or natural environments at low concentrations. Such low toxin doses are regularly associated with hormesis, i.e., growth stimulation, and they are suspected to affect mortality and within-population plant size distribution in dense plant stands. However, it is not known whether all these low-dose effects exist when plants grow in soil. We exposed barley to a range of low glyphosate doses and let the plants grow in dense stands for several weeks in soil. Six experiments were done that contained altogether 10,260 seedlings in 572 pots. We evaluated if the changes in average biomass and shoot length occur at the same concentrations as do the effects on slow- and fast-growing individuals, if seed size or early vigor explains variation in the response to glyphosate, and if low toxin doses change within-population mortality. Plant biomass, length and survival of subpopulations changed at doses that did not affect mean biomass. Effects of early vigor faded early, but differences in seed size and particularly vegetative growth had impacts: fast-growing plants hardly showed hormesis, whereas hormesis was particularly strong among slow-growing individuals. Compared to the population mean, glyphosate effects started at lower doses among slow-growing individuals and at higher doses among fast-growing individuals. Several times higher doses were needed before the fast-growing individuals showed the same toxicity as most of the population. Low toxin doses regularly enhanced the growth of the smallest individuals, which reduced size variation within populations and was associated with a higher number of surviving plants. Indeed, in one experiment self-thinning was not observed at low doses that stimulated the growth of slow-growing plants. As glyphosate levels in this study match those observed in agricultural fields and natural environments, we conclude that even low-levels of agro-environmental contamination are likely to shape phenotypic response, which might lead to adaptation and cascading ecological impacts.

Exposure to Nitro-PAHs interfere with germination and early growth of Hordeum vulgare via oxidative stress

Nitrated polycyclic aromatic hydrocarbons (Nitro-PAHs) as important organic pollutants are ubiquitous in the atmospheric environment, agricultural soils and aquatic environments to pose a severe polluting risk. However, little is known about the mechanism of Nitro-PAHs genotoxicity in plants. We analyzed seeds germination, seedlings growth, and toxicity mechanism following 1-Nitropyrene treatment in Hordeum vulgare. Our results reveal that 1-NP treatment could be an inhibited agent on seeds germination and growth of roots and shoots. Additionally, the reduction of mitotic index and the increasing frequency of micronucleus suggest that 1-NP may pose a potential risk of genotoxicity in the plant. We further clarify that O₂^- and H₂O₂ radicals contribute to 1-NP stimulation induced oxidative damage. Our study provides insights into the role of Nitro-PAHs exposure on growth processing toxicity and genotoxicity in plant and provided a useful reference for the surveillance and risk management of Nitro-PAHs in environments.

Copper alleviates cobalt toxicity in barley by antagonistic interaction of the two metals

Cobalt (Co) commonly co-exists with copper (Cu) in natural soils, but the information about their combined effects on plants is poorly available. In this study, we hydroponically investigated the combined effects of Co and Cu on two barley genotypes differing in Co toxicity tolerance to reveal the interaction pattern of these two metals. The results showed that single treatment of Co or Cu at the dose of 100 μM led to a significant decrease of growth and photosynthetic rate, and a significant increase of lipid peroxidation, ROS radicals as well as anti-oxidative enzyme (SOD, CAT and GR) activities and glutathione content, with the extent of effect being less in Yan66 than Ea52. The combined treatment of Co and Cu alleviated the toxicity of both metals in comparison with each metal treatment alone, as reflected by improved growth and photosynthesis, and much slight oxidative stress. The alleviation of metal toxicity upon combined treatment is mainly attributed to a drastic reduction of Co uptake and its translocation from roots to shoots. It may be suggested that interaction of Co and Cu on their uptake and movement in plants is antagonistic.

Synergistic Phytotoxic Effects of Culmorin and Trichothecene Mycotoxins

Species of the fungus Fusarium cause Fusarium head blight (FHB) of cereal crops and contaminate grain with sesquiterpenoid mycotoxins, including culmorin (CUL) and trichothecenes. While the phytotoxicity of trichothecenes, such as deoxynivalenol (DON), and their role in virulence are well characterized, less is known about the phytotoxicity of CUL and its role in the development of FHB. Herein, we evaluated the phytotoxic effects of purified CUL and CUL-trichothecene mixtures using Chlamydomonas reinhardtii growth and Triticum aestivum (wheat) root elongation assays. By itself, CUL did not affect growth in either system. However, mixtures of CUL with DON, 3-acetyldeoxynivalenol, 15-acetyldeoxynivalenol, or NX-3, but not with nivalenol, inhibited growth in a synergistic manner. Synergistic phytotoxic effects of CUL and DON were also observed on multiple plant varieties and species. The severity of wheat FHB caused by 15 isolates of Fusarium graminearum was negatively correlated with the CUL/DON ratio, but positively correlated with the sum of both CUL and DON. Additionally, during the first week of infection, CUL biosynthetic genes were more highly expressed than the TRI5 trichothecene biosynthetic gene. Furthermore, genomic analysis of Fusarium species revealed that CUL and trichothecene biosynthetic genes consistently co-occur among species closely related to F. graminearum.

Uptake and translocation of magnetite (Fe3O4) nanoparticles and its impact on photosynthetic genes in barley (Hordeum vulgare L.)

This study investigates the fate and impact of iron oxide or magnetite (Fe₃O₄, ∼13 nm in size) nanoparticles (NPs) in barley (Hordeum vulgare L.), a common crop cultivated around the world. Barley seedlings were grown in hydroponic culture for three weeks to include NPs (125, 250, 500, and 1000 mg/L). Transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) techniques were used to assess their uptake and translocation. Photosynthesis marker genes were quantified by RT-qPCR. Results revealed that increasing doses of Fe₃O₄ NPs were gradually enhanced the plant growth up to 500 mg/L, which promoted the fresh weight (FW) respectively ∼19% and ∼88% for leaf and root tissues than the ones for control. No phytotoxic effect was recorded even at high NPs doses. NPs inclusion increased some phenological parameters such as chlorophyll, total soluble protein, number of chloroplasts, and dry weight. High NPs doses dramatically reduced the catalase activity and hydrogen peroxide content, suggesting a possible function of NPs as nanozyme in vivo. TEM observations showed that Fe₃O₄ NPs penetrated and internalized in the root cells. In leaves, they were mostly existed at the surrounding cell wall, suggesting their translocation from root to shoot without cellular penetration. Further analysis by using VSM confirmed the existence of Fe₃O₄ NPs in leaves which result in dramatic alterations of the photosystem genes (PetA, psaA, BCA and psbA). In conclusion, barley plants uptake and translocate Fe₃O₄ NPs, which promoted the plant growth probably due to the promoted gene expression and efficient photosynthetic activity.