Response Of Barley Research Articles

Partial root‐zone drying irrigation enhances synthesis of glutathione in barley roots to improve low temperature tolerance

SUMMARYPartial root‐zone drying irrigation (PRD) has been widely employed to regulate crop root development and responses to environmental fluctuations. However, its role in reprogramming rhizospheric microorganisms and inducing plant stress tolerance remains largely unexplored. This study aimed to investigate the effects of PRD on the response of barley (Hordeum vulgare) plants to low temperatures under various irrigation regimes. Under low temperature, barley plants subjected to PRD exhibited a significantly enhanced net photosynthetic rate, stomatal conductance, and maximum quantum efficiency of photosystem II compared to fully irrigated plants. Additionally, these plants showed a reduction in relative conductance. These results suggest that PRD could be a viable strategy for enhancing crop stress tolerance through irrigation management. Metabolomic analysis revealed that PRD influenced the accumulation of glutathione and 9‐octadecenamide in roots under low temperature, which was corroborated by transcriptome profiling data. Furthermore, the study highlighted the close association between this regulatory process and rhizosphere core microorganisms, such as Sphingobium and Mortierella, enriched in barley roots under PRD. This study revealed the mechanism underlying plant stress tolerance induction by PRD and the roles of rhizosphere microorganisms in this process. Also, the current study suggests that PRD is a promising strategy for enhancing crop stress tolerance through effective irrigation management.

To divide or not to divide? NAC8 (SOG1) as a key regulator of DNA Damage Response in barley (Hordeum vulgare L.)

To divide or not to divide? NAC8 (SOG1) as a key regulator of DNA Damage Response in barley (Hordeum vulgare L.)

Effect of fertility levels and liquid biofertilizers on quality parameters of malt barley (Hordeum vulgare L.)

Barley (Hordeum vulgare L.) is crucial for malt production in the beverage industry, driving the need for sustainable practices to improve grain yield and quality. Fertility management and biofertilizers enhance nutrient availability and soil health, but their combined effects on 1malt barley quality require further study. A field experiment was conducted during rabi season 2020–21 and 2021–22 with the objective to evaluate the response of malt barley to fertility levels and biofertilizers. The experiment was laid out in randomized block design (Factorial) with 15 treatment combinations comprised of three fertility levels, i.e. application of 70 kg N + 40 kg P2 O5 + 25 kg K2 O/ha, 60 kg N + 30 kg P2O5 + 20 kg K2 O/ha and 50 kg N + 25 kg P2O5 + 15 kg K2O/ha with 5 liquid biofertilizers, i.e. control, Azotobacter, PSB, KMB and Azotobacter + PSB + KMB. The result revealed that malt barley crop fertilized with 70 kg N + 40 kg P2 O5 + 25 kg K2O/ha recorded highest protein content (11.6%) and average grain weight (43.8 mg) which was significantly higher over rest of fertility levels. While the highest starch (61.8%) and malt content (82.6%) in grain recorded under application of 50 kg N + 25 kg P2O5 + 15 kg K2 O/ha. The results showed that seed inoculation with liquid biofertilizers Azotobacter + PSB + KMB significantly improved protein content (11.4%) and average grain weight (43.6 mg) of malt barley crop. While the highest starch (62.0%) and malt content (82.7%) in grain recorded under control. The study concludes that higher fertility levels and combined biofertilizer application (Azotobacter + PSB + KMB) enhance protein content and grain weight in malt barley, while lower fertility levels favour higher starch and malt content.

Association mapping of drought stress response for yield and quality traits in barley

AbstractBarley (Hordeum vulgare L.) is a major cereal crop grown worldwide for human consumption, malting, and animal feed. Drought is one of the major abiotic stresses that reduce grain yield and quality in barley. This study was conducted to evaluate a set of 250 barley lines grown under irrigated, water‐stressed, and rainfed conditions and to identify genomic regions associated with 10 traits related to grain yield and quality across eight independent field environments. Variability was observed among barley lines for tolerance to water‐stressed conditions in all tested environments. Genotype and environment both contributed to the phenotypic variation of the barley lines. Population structure analysis identified two subpopulations using 20,700 single nucleotide polymorphism (SNP) markers. Genome‐wide association mapping detected 74 significant SNPs (p ≤ 6.5 × 10−6), representing 14 quantitative trait loci (QTLs), on all barley chromosomes, except 3H. The QTL, QBG.ARS.7H, associated with beta‐glucan (BG), was consistently detected across environments and explained 13.93% of phenotypic variation. Carriers of the minor allele for the BG‐associated SNP, JHI‐Hv50k‐2016‐488035, exhibited up to 14.65% higher BG content, on average, compared with carriers of the common allele. This study advances our understanding of the genetics of barley response to water‐stress conditions and suggests molecular markers for QTL, which may be used in barley improvement.

Growth, Yield, and Photosynthetic Dry Matter Remobilization Response of Barley to Plant Growth Promoting Rhizobacteria (PGPR) and Nitrogen

A two-year factorial experiment based on a randomized complete block design with three replicates was carried out on barley cultivar LB-IRAN at the research farm of the Islamic Azad University, Ardabil, Iran, during the cropping years of 2019–2021, in order to survey the impact of plant growth-promoting rhizobacteria (PGPR) and nitrogen fertilizer on growth, yield, and remobilization of photosynthetic dry matter in barley. The first factor included five nitrogen levels: 0 (control), 25, 50, 75, 100 kg/ha net nitrogen; the second factor contained grain inoculations with four bacteria: no inoculation (control), Azotobacter chroococcum race 5, Azospirillum lipoferum race of, and a combination of the two mentioned bacteria. Fertilization was performed at the planting, tillering, and grain filling stages. Results revealed that the number of plant/m2, tiller per plant, 1000 grain weight, grain per spike, grain yield per unit area, biological yield, rate of dry matter remobilization from stem to the grain, contribution of dry matter remobilization from stem to the grain, rate of remobilization from whole of the plant to the grain, contribution of remobilization from whole of the plant to the grain, single grain weight, and harvest index significantly increased. Nitrogen rate increment resulted in the higher rates of the above-mentioned traits as 100 kg/ha nitrogen significantly showed the highest amounts while control showed the least. Combined treatment of the bacteria resulted in a higher rates as compared to the single bacteria, and the control showed the lowest amounts. It was also observed that application of 100 kg/ha nitrogen on Azotobacter chroococcum race 5 and Azospirillum lipoferum race of resulted in the lowest rate of dry matter remobilization from the stem and whole plant to the grain as well as the contribution of dry matter remobilization from the stem and whole plant to the grain, while control treatments of nitrogen and of PGPRs caused the highest rates. Difference between the highest and lowest rates of grain yield was observed by applying nitrogen (24%) and PGPRs (40%).

Field versus controlled environmental experiments to evaluate the heat stress response of barley (Hordeum vulgare L.)

The complexity of heat stress hinders both the exploration of the genetic basis of stress response and breeding of genotypes with increased stress tolerance. Our main goal was to analyze and compare the possibilities of evaluating heat stress responses of barley cultivars in field sowing and controlled environmental experiments. For this purpose, a four-year field-sown experiment was carried out at one location in a panel of 190 winter and facultative barleys. In parallel, a subset of 28 cultivars were included into controlled environmental tests, where their reactions were determined to single heat stress treatment applied at heading and to combined heat stresses applied at first node appearance and then at heading. Based on the grain-yield related parameters, seven distinct clusters of the cultivars could be established with specific reaction patterns across the years. There was one year with close to optimal weather conditions and one year, when heat stress occurred during flowering and grain setting, making it possible to evaluate the heat stress responses of the 190 barley genotypes. In the heat stress prone 2022 year, the general trends were a strong reduction in the reproductive tiller number and a slight reduction in the fertility. In several groups, these negative effects were compensated with significant increases in grain number per ears and with strong increases in the average grain weight. Under controlled conditions, heat stress significantly reduced most of the grain-yield related traits. Among the more tolerant genotypes, two basic response types could be distinguished. One group was able to better preserve the grain number and weight in the main ear under heat stress, while the other was more able to allocate resources into the side tillers during the recovery period. In the combined heat stress, the average trait values were similar to those in the single stress or even lower, and there was no general priming effect clearly detectable. In the case of the 28 genotypes, there were significant correlations between the stress-induced changes in grain-yield related traits measured under field and under controlled conditions, underlining the possibility of combining the information originating from the two different environments.

Impact nano- and micro- form of CdO on barley growth and oxidative stress response

The objective was investigated the effects of CdO and nano-CdO as potential toxic pollutants on growth and redox response of barley. CdO and nano-CdO have been found to cause significant phytotoxicity in barley seedlings, with nano-CdO increasing plant tissue cadmium accumulation. This accumulation is linked to growth retardation and oxidative stress. Low molecular weight antioxidants like restored glutathione and ascorbate have been found to increase the activity of glutathione peroxidase (GPX), glutathione-S-transferase (GSTs), and ascorbate peroxidase (APX) in green tissues. Catalase (CAT) activity increased from 50 % with 100 mg/l CdO to 70 % with 1000 mg/l and nano-CdO. The observed disturbance in redox balance signals the upregulation of corresponding genes. Antioxidant enzyme isoform gene transcripts increased for SODB, CAT2, and APX. Cadmium buildup in root cells causes oxidative stress, leading to upregulation of SOD, CAT, GR, and GSTs isoform genes as well as protein carbonylation, sulfhydryl group degradation, and MDA accumulation. CdO and nano-CdO have similar phytotoxic effects, but bioavailability affects biochemical and molecular responses.

Evaluating waterlogging stress response and recovery in barley (Hordeum vulgare L.): an image-based phenotyping approach

Waterlogging is expected to become a more prominent yield restricting stress for barley as rainfall frequency is increasing in many regions due to climate change. The duration of waterlogging events in the field is highly variable throughout the season, and this variation is also observed in experimental waterlogging studies. Such variety of protocols make intricate physiological responses challenging to assess and quantify. To assess barley waterlogging tolerance in controlled conditions, we present an optimal duration and setup of simulated waterlogging stress using image-based phenotyping. Six protocols durations, 5, 10, and 14 days of stress with and without seven days of recovery, were tested. To quantify the physiological effects of waterlogging on growth and greenness, we used top down and side view RGB (Red-Green-Blue) images. These images were taken daily throughout each of the protocols using the PSI PlantScreen™ imaging platform. Two genotypes of two-row spring barley, grown in glasshouse conditions, were subjected to each of the six protocols, with stress being imposed at the three-leaf stage. Shoot biomass and root imaging data were analysed to determine the optimal stress protocol duration, as well as to quantify the growth and morphometric changes of barley in response to waterlogging stress. Our time-series results show a significant growth reduction and alteration of greenness, allowing us to determine an optimal protocol duration of 14 days of stress and seven days of recovery for controlled conditions. Moreover, to confirm the reproducibility of this protocol, we conducted the same experiment in a different facility equipped with RGB and chlorophyll fluorescence imaging sensors. Our results demonstrate that the selected protocol enables the assessment of genotypic differences, which allow us to further determine tolerance responses in a glasshouse environment. Altogether, this work presents a new and reproducible image-based protocol to assess early stage waterlogging tolerance, empowering a precise quantification of waterlogging stress relevant markers such as greenness, Fv/Fm and growth rates.

Metabolomics, phytohormone and transcriptomics strategies to reveal the mechanism of barley heading date regulation to responds different photoperiod

BackgroundThe correlation between heading date and flowering time significantly regulates grain filling and seed formation in barley and other crops, ultimately determining crop productivity. In this study, the transcriptome, hormone content detection, and metabolome analysis were performed systematically to analyze the regulatory mechanism of heading time in highland barley under different light conditions. The heading date of D18 (winter highland barley variety, Dongqing18) was later than that of K13 (vernal highland barley variety) under normal growth conditions or long-day (LD) treatment, while this situation will reverse with short-day (SD) treatment.ResultsThe circadian rhythm plant, plant hormone signaling transduction, starch and sucrose metabolism, and photosynthesis-related pathways are significantly enriched in barley under SD and LD to influence heading time. In the plant circadian rhythm pathway, the key genes GI (Gigantea), PRR (Pesudoresponseregulator), FKF1 (Flavin-binding kelch pepeat F-Box 1), and FT (Flowering locus T) are identified as highly expressed in D18SD3 and K13SD2, while they are significantly down-regulated in K13SD3. These genes play an important role in regulating the heading date of D18 earlier than that of K13 under SD conditions. In photosynthesis-related pathways, a-b binding protein and RBS were highly expressed in K13LD3, while NADP-dependent malic enzyme, phosphoenolpyruvate carboxylase, fructose-bisphosphate aldolase, and triosephosphate isomerase were significantly expressed in D18SD3. In the starch and sucrose metabolism pathway, 41 DEGs (differentially expressed genes) and related metabolites were identified as highly expressed and accumulated in D18SD3. The DEGs SAUR (Small auxin-up RNA), ARF (Auxin response factor), TIR1 (Transport inhibitor response 1), EIN3 (Ethylene-insensitive 3), ERS1 (Ethylene receptor gene), and JAZ1 (Jasmonate ZIM-domain) in the plant hormone pathway were significantly up-regulated in D18SD3. Compared with D18LD3, the content of N6-isopentenyladenine, indole-3-carboxylic acid, 1-aminocyclopropanecarboxylic acid, trans-zeatin, indole-3-carboxaldehyde, 1-O-indol-3-ylacetylglucose, and salicylic acid in D18SD3 also increased. The expression levels of vernalization genes (HvVRN1, HvVRN2, and HvVRN3), photoperiod genes (PPD), and PPDK (Pyruvate phosphate dikinase) that affect photosynthetic efficiency in barley are also analyzed, which play important regulatory roles in barley heading date. The WGCNA analysis of the metabolome data and circadian regulatory genes identified the key metabolites and candidate genes to regulate the heading time of barley in response to the photoperiod.ConclusionThese studies will provide a reference for the regulation mechanism of flowering and the heading date of highland barley.

Response of Malt Barley to NPSZnB and Urea Fertilizers Across Soil Types and Agro-ecologies, Arsi Zone of Oromia, South-Eastern Ethiopia

Field trials were conducted on farmers’ fields during the 2017, 2018, and 2019 cropping seasons to determine the optimum NPSZnB and urea fertilizer rates for selected crop, soil, and climatic conditions, as well as to assess the economic feasibility of blended and urea fertilizer rates for malt barley by varying levels of NPSZnB fertilizer (0, 100, 150, 200, 250 kg ha-1) and recommended NP in combined RCBD with three replications on growth performance and yield. The post-harvest soil analysis results of experimental sites revealed that the use of treatments significantly (p< 0.05 and p< 0.001) altered pH, total N, available P, and organic matter for samples taken from malt barley crop experimental sites. Application of different fertilizer levels significantly affected post-harvest pH and organic carbon contents. A significant improvement was observed in soil chemical contents compared to the contents of the soil before treatment application at Lemu-Bilbilo district. Combined levels of NPSZnB and urea fertilizer rates significantly affected grain and above-ground biomass yields at Lemu-Bilbilo and Kofele districts. The maximum grain and biomass yield (6197 and 11018 kg ha-1) in 2019 and minimum (3646 and 6875 kg ha-1) in the 2018 cropping season were obtained, respectively at Lemu-Bilbilo district up on the application of NPSZnB and urea fertilizers. Similarly, significant grain and biomass yield (5554 and 10412 kg ha-1) were obtained from the application of 250 + 200 and 250 + 150 kg ha-1 NPSZnB with urea fertilizer, respectively. The maximum grain and biomass yield (5244 and 10092 kg ha-1) in 2019 and minimum (3477 and 7736 kg ha-1) in 2017 and 2018 cropping season were obtained, respectively at Kofele district from the application of NPSZnB and urea fertilizers. Similarly, a significant grain and biomass yield (5125 and 9826 kg ha-1) were obtained from the application of 250 + 150 and 250 + 200 kg ha-1 NPSZnB + urea, respectively.

LncRNA cis- and trans-regulation provides new insight into drought stress responses in wild barley.

Drought is one of the most common abiotic stresses that affect barley productivity. Long noncoding RNA (lncRNA) has been reported to be widely involved in abiotic stress, however, its function in the drought stress response in wild barley remains unclear. In this study, RNA sequencing was performed to identify differentially expressed lncRNAs (DElncRNA) among two wild barley and two cultivated barley genotypes. Then, the cis-regulatory networks were according to the chromosome position and the expression level correction. The GO annotation indicates that these cis-target genes are mainly involved in "ion transport transporter activity" and "metal ion transport transporter activity". Through weighted gene co-expression network analysis (WGCNA), 10 drought-related modules were identified to contract trans-regulatory networks. The KEGG annotation demonstrated that these trans-target genes were enriched for photosynthetic physiology, brassinosteroid biosynthesis, and flavonoid metabolism. In addition, we constructed the lncRNA-mediated ceRNA regulatory network by predicting the microRNA response elements (MREs). Furthermore, the expressions of lncRNAs were verified by RT-qPCR. Functional verification of a candidate lncRNA, MSTRG.32128, demonstrated its positive role in drought response and root growth and development regulation. Hormone content analysis provided insights into the regulatory mechanisms of MSTRG.32128 in root development, revealing its involvement in auxin and ethylene signal transduction pathways. These findings advance our understanding of lncRNA-mediated regulatory mechanisms in barley under drought stress. Our results will provide new insights into the functions of lncRNAs in barley responding to drought stress.

Mineral accumulation, relative water content and gas exchange are the main physiological regulating mechanisms to cope with salt stress in barley

Salinity has become a major environmental concern for agricultural lands, leading to decreased crop yields. Hence, plant biology experts aim to genetically improve barley’s adaptation to salinity stress by deeply studying the effects of salt stress and the responses of barley to this stress. In this context, our study aims to explore the variation in physiological and biochemical responses of five Tunisian spring barley genotypes to salt stress during the heading phase. Two salinity treatments were induced by using 100 mM NaCl (T1) and 250 mM NaCl (T2) in the irrigation water. Significant phenotypic variations were detected among the genotypes in response to salt stress. Plants exposed to 250 mM of NaCl showed an important decline in all studied physiological parameters namely, gas exchange, ions concentration and relative water content RWC. The observed decreases in concentrations ranged from, approximately, 6.64% to 40.76% for K+, 5.91% to 43.67% for Na+, 14.12% to 52.38% for Ca2+, and 15.22% to 38.48% for Mg2+ across the different genotypes and salt stress levels. However, under salinity conditions, proline and soluble sugars increased for all genotypes with an average increase of 1.6 times in proline concentrations and 1.4 times in soluble sugars concentration. Furthermore, MDA levels rose also for all genotypes, with the biggest rise in Lemsi genotype (114.27% of increase compared to control). Ardhaoui and Rihane showed higher photosynthetic activity compared to the other genotypes across all treatments. The stepwise regression approach identified potassium content, K+/Na+ ratio, relative water content, stomatal conductance and SPAD measurement as predominant traits for thousand kernel weight (R2 = 84.06), suggesting their significant role in alleviating salt stress in barley. Overall, at heading stage, salt accumulation in irrigated soils with saline water significantly influences the growth of barley by influencing gas exchange parameters, mineral composition and water content, in a genotype-dependent manner. These results will serve on elucidating the genetic mechanisms underlying these variations to facilitate targeted improvements in barley's tolerance to salt stress.

Sea Barley (Hordeum Marinum) Seed Germination Ecology and Seedling Emergence

Sea barley is weedy grass in agricultural landscapes and infrastructure habitats (roads, railroads, etc.) in Golestan province (the northern part of Iran). This study investigated the germination of sea barley in response to temperature, water potentials, salinity, pH levels, waterlogging, heat stress and also seedling emergence in response to burial depth. Results showed that sea barley seeds germinated over a wide range of temperatures from 5 to 35 °C, with the highest germination at 25 °C. Seed germination was rapidly reduced with increasing osmotic potential so that germination declined by 36% at –0.2 MPa. This was also the case for the salinity stress, and germination declined by 30% at 40 mM NaCl. Seed germination was the highest (> 65%) in 6 to 7 pHs and no germination was observed at alkali levels. Heat stress completely inhibited the germination of seeds at all tested temperatures and durations. Sea barley seed germination was higher than 50% after being waterlogged for 45 days, and some germination (12%) still occurred 60 days after waterlogging. The highest seedling growth occurred at 1–2 cm soil depth and was negligible at ≥5 cm soil depths. The results of this study indicate that deep tillage or flamethrower may be good options to mitigate the negative impacts of this weed.

IMPACT OF SOIL STERILIZATION FROM DIFFERENT LOCATIONS, WHEAT SEEDS CLEANING AND THEIR INTERACTIONS ON WEED CONTROL, AND YIELD AND YIELD COMPONENTS

IMPACT OF SOIL STERILIZATION FROM DIFFERENT LOCATIONS, WHEAT SEEDS CLEANING AND THEIR INTERACTIONS ON WEED CONTROL, AND YIELD AND YIELD COMPONENTS

Cadmium toxicity promotes hormonal imbalance and induces the expression of genes involved in systemic resistances in barley.

Cadmium (Cd) is a widely distributed pollutant that adversely affects plants' metabolism and productivity. Phytohormones play a vital role in the acclimation of plants to metal stress. On the other hand, phytohormones trigger systemic resistances, including systemic acquired resistance (SAR) and induced systemic resistance (ISR), in plants in response to biotic interactions. The present study aimed to investigate the possible induction of SAR and ISR pathways in relation to the hormonal alteration of barley seedlings in response to Cd stress. Barley seedlings were exposed to 1.5mgg-1 Cd in the soil for three days. The nutrient content, oxidative status, phytohormones profile, and expression of genes involved in SAR and ISR pathways of barley seedlings were examined. Cd accumulation resulted in a reduction in the nutrient content of barley seedlings. The specific activity of superoxide dismutase and the hydrogen peroxide content significantly increased in response to Cd toxicity. Abscisic acid, jasmonic acid, and ethylene content increased under Cd exposure. Cd treatment resulted in the upregulation of NPR1, PR3, and PR13 genes in SAR pathways. The transcripts of PAL1 and LOX2.2 genes in the ISR pathway were also significantly increased in response to Cd treatment. These findings suggest that hormonal-activated systemic resistances are involved in the response of barley to Cd stress.

"Response of Malt Barley to NPSB and Urea Fertilizers Across Soil Types and Agro-Ecologies, Arsi Zone of Oromia, South-Eastern Ethiopia"

"Response of Malt Barley to NPSB and Urea Fertilizers Across Soil Types and Agro-Ecologies, Arsi Zone of Oromia, South-Eastern Ethiopia"

Intensified Selection, Elevated Mutations, and Reduced Adaptation Potential in Wild Barley in Response to 28 Years of Global Warming

Many studies have investigated the threat of climate change on wild plants, but few have investigated the genetic responses of crop wild relative populations under threat. We characterized the genetic responses of 10 wild barley (Hordeum spontaneum K. Koch) populations in Israel, sampling them in 1980 and again in 2008, through exome capture and RNA-Seq analyses. Sequencing 48 wild barley samples of these populations representing two collection years generated six million SNPs, and SNP annotations identified 12,926 and 13,361 deleterious SNPs for 1980 and 2008 samples, respectively. The assayed wild barley samples displayed intensified selective sweeps and elevated deleterious mutations across seven chromosomes in response to 28 years of global warming. On average, the 2008 samples had lower individual and population mutational burdens, but the population adaptation potential was estimated to be lower in samples from 2008 than in 1980. These findings highlight the genetic risks of losing wild barley under global warming and support the need to conserve crop wild relatives.

Co3O4 Nanostructured Sensor for Electrochemical Detection of H2O2 as a Stress Biomarker in Barley: Fe3O4 Nanoparticles-Mediated Enhancement of Salt Stress Tolerance.

This research investigates the enhancement of barley's resistance to salt stress by integrating nanoparticles and employing a nanostructured Co3O4 sensor for the electrochemical detection of hydrogen peroxide (H2O2), a crucial indicator of oxidative stress. The novel sensor, featuring petal-shaped Co3O4 nanostructures, exhibits remarkable precision and sensitivity to H2O2 in buffer solution, showcasing notable efficacy in complex analytes like plant juice. The research establishes that the introduction of Fe3O4 nanoparticles significantly improves barley's ability to withstand salt stress, leading to a reduction in detected H2O2 concentrations, alongside positive impacts on morphological parameters and photosynthesis rates. The developed sensor promises to provide real-time monitoring of barley stress responses, providing valuable information on increasing tolerance to crop stressors.

Barley preferentially activates strategy-II iron uptake mechanism under iron deficiency

Plants utilize two main strategies for iron (Fe) uptake from the rhizosphere. Strategy-I is based on the reduction of ferric (Fe3+) to ferrous (Fe2+) iron by ferric chelate reductase (FCR) and is mainly observed in dicots. Strategy-II utilizes the complexation of Fe3+ with phytosiderophores secreted from the plant roots and mainly evolved in Gramineous species, including barley (Hordeum vulgare). Recent studies suggest that some species use a combination of both strategies for more efficient Fe uptake. However, the preference of barley for these strategies is not well understood. This study investigated the physiological and biochemical responses of barley under iron deficiency and examined the expression levels of the genes involved in Strategy-I and Strategy-II mechanisms in the roots. Fe deficiency led to decreased root and shoot lengths, fresh and dry weights, and Fe accumulation in the roots. Parallel to the chlorosis observed in the leaves, FCR activity and rhizosphere acidification were also significantly reduced in the roots, while the release of phytosiderophores increased. Furthermore, Strategy-II genes expressed higher than the Strategy-I genes in the roots under Fe deficiency. These findings demonstrate that Strategy-II is more activated than Strategy-I for Fe uptake in barley roots under Fe-deficient conditions.

Zeocin-induced DNA damage response in barley and its dependence on ATR

DNA damage response (DDR) is an essential mechanism by which living organisms maintain their genomic stability. In plants, DDR is important also for normal growth and yield. Here, we explored the DDR of a temperate model crop barley (Hordeum vulgare) at the phenotypic, physiological, and transcriptomic levels. By a series of in vitro DNA damage assays using the DNA strand break (DNA-SB) inducing agent zeocin, we showed reduced root growth and expansion of the differentiated zone to the root tip. Genome-wide transcriptional profiling of barley wild-type and plants mutated in DDR signaling kinase ATAXIA TELANGIECTASIA MUTATED AND RAD3-RELATED (hvatr.g) revealed zeocin-dependent, ATR-dependent, and zeocin-dependent/ATR-independent transcriptional responses. Transcriptional changes were scored also using the newly developed catalog of 421 barley DDR genes with the phylogenetically-resolved relationships of barley SUPRESSOR OF GAMMA 1 (SOG1) and SOG1-LIKE (SGL) genes. Zeocin caused up-regulation of specific DDR factors and down-regulation of cell cycle and histone genes, mostly in an ATR-independent manner. The ATR dependency was obvious for some factors associated with DDR during DNA replication and for many genes without an obvious connection to DDR. This provided molecular insight into the response to DNA-SB induction in the large and complex barley genome.