Inferring regulatory element landscapes and gene regulatory networks from integrated analysis in eight hulless barley varieties under abiotic stress.

BACKGROUND: The cis-regulatory element became increasingly important for resistance breeding. There were many DNA variations identified by resequencing. To investigate the links between the DNA variations and cis-regulatory element was the fundamental work. DNA variations in cis-regulatory elements caused phenotype variations in general. RESULTS: We used WGBS, ChIP-seq and RNA-seq technology to decipher the regulatory element landscape from eight hulless barley varieties under four kinds of abiotic stresses. We discovered 231,440 lowly methylated regions (LMRs) from the methylome data of eight varieties. The LMRs mainly distributed in the intergenic regions. A total of 97,909 enhancer-gene pairs were identified from the correlation analysis between methylation degree and expression level. A lot of enriched motifs were recognized from the tolerant-specific LMRs. The key transcription factors were screened out and the transcription factor regulatory network was inferred from the enhancer-gene pairs data for drought stress. The NAC transcription factor was predicted to target to TCP, bHLH, bZIP transcription factor genes. We concluded that the H3K27me3 modification regions overlapped with the LMRs more than the H3K4me3. The variation of single nucleotide polymorphism was more abundant in LMRs than the remain regions of the genome. CONCLUSIONS: Epigenetic regulation is an important mechanism for organisms to adapt to complex environments. Through the study of DNA methylation and histone modification, we found that many changes had taken place in enhancers and transcription factors in the abiotic stress of hulless barley. For example, transcription factors including NAC may play an important role. This enriched the molecular basis of highland barley stress response.

The draft genome of Tibetan hulless barley reveals adaptive patterns to the high stressful Tibetan Plateau.

The Tibetan hulless barley (Hordeum vulgare L. var. nudum), also called "Qingke" in Chinese and "Ne" in Tibetan, is the staple food for Tibetans and an important livestock feed in the Tibetan Plateau. The diploid nature and adaptation to diverse environments of the highland give it unique resources for genetic research and crop improvement. Here we produced a 3.89-Gb draft assembly of Tibetan hulless barley with 36,151 predicted protein-coding genes. Comparative analyses revealed the divergence times and synteny between barley and other representative Poaceae genomes. The expansion of the gene family related to stress responses was found in Tibetan hulless barley. Resequencing of 10 barley accessions uncovered high levels of genetic variation in Tibetan wild barley and genetic divergence between Tibetan and non-Tibetan barley genomes. Selective sweep analyses demonstrate adaptive correlations of genes under selection with extensive environmental variables. Our results not only construct a genomic framework for crop improvement but also provide evolutionary insights of highland adaptation of Tibetan hulless barley.

Transcriptomics analysis of hulless barley during grain development with a focus on starch biosynthesis.

Hulless barley, with its unique nutritional value and potential health benefits, has increasingly attracted attentions in recent years. However, the transcription dynamics during hulless barley grain development is not well understood. In the present study, we investigated the transcriptome changes during barley grain development using Illumina paired-end RNA-sequencing. Two datasets of the developing grain transcriptomes from two barley landraces with the differential seed starch synthesis traits were generated, and comparative transcriptome approach in both genotypes was performed. The results showed that 38 differentially expressed genes (DEGs) were found co-modulated in both genotypes during the barley grain development. Of those, the proteins encoded by most of those DGEs were found, such as alpha-amylase-related proteins, lipid-transfer protein, homeodomain leucine zipper (HD-Zip), NUCLEAR FACTOR-Y, subunit B (NF-YBs), as well as MYB transcription factors. More interestingly, two genes Hvulgare_GLEAN_10012370 and Hvulgare_GLEAN_10021199 encoding SuSy, AGPase (Hvulgare_GLEAN_10033640 and Hvulgare_GLEAN_10056301), as well as SBE2b (Hvulgare_GLEAN_10018352) were found to significantly contribute to the regulatory mechanism during grain development in both genotypes. Moreover, six co-expression modules associated with specific biological processes or pathways (M1 to M6) were identified by consensus co-expression network. Significantly enriched pathways of those module genes showed difference in both genotypes. These results will expand our understanding of the complex molecular mechanism of starch synthesis during barley grain development.

A microsatellite diversity analysis and the development of core-set germplasm in a large hulless barley (Hordeum vulgare L.) collection.

BACKGROUND: Clarifying genetic diversity in a large germplasm resource plays important roles in experimental designs that provides flexible utility in fundamental research and breeding in crops. However, the work is limited due to small collections of barley that are insufficient representatives. RESULTS: In the present study, we collected 562 hulless barley (Hordeum vulgare L.) accessions with worldwide geographic origins and evaluated their genetic variability and relatedness based on 93 simple sequence repeat (SSR) markers. In an integrated analysis of the population structure, analysis of molecular variance (AMOVA) and pairwise F ST, the 562 barley accessions exhibited a strong stratification that allowed for them to be divided into two major subpopulations (p1 and p2) and an admixture subpopulation, with 93, 408 and 61 accessions, respectively. In a neutral test, considerable proportions of SSR alleles expressed the strong non-neutrality in specific subpopulations (44 and 37), which are probably responsible for population differentiation. To reduce the diversity redundancy in large barley collections, we delicately selected a core set of 200 barley accessions as a tradeoff between diversity and representativeness in an easily handled population. In comparing the 562 barley accessions, the core barley set accounted for 96.2% of allelic diversity and 93% to 95% of phenotypic variability, whereas it exhibited a significant enhancement in minor allelic frequencies, which probably benefit association mapping in the barley core set. CONCLUSIONS: The results provided additional insight into the genetic structure in a large barley germplasm resource, from which an easily manageable barley core set was identified, demonstrating the great potential for discovering key QTLs and ultimately facilitating barley breeding progress.

Transcriptome analysis revealed the drought-responsive genes in Tibetan hulless barley.

BACKGROUND: Hulless barley, also called naked barley, is an important cereal crop worldwide, serving as a healthy food both for human consumption and animal feed. Nevertheless, it often suffered from drought stress during its growth and development, resulting in a drastic reduction in barley yields. Therefore, study on molecular mechanism of hulless barley drought-tolerance is very important for increasing barley production. To investigate molecular mechanism of barley drought-resistance, this study examined co-regulated mRNAs that show a change in expression pattern under early well water, later water deficit and finally water recovery treatments, and to identify mRNAs specific to water limiting conditions. RESULTS: Total of 853 differentially expressed genes (DEGs) were detected and categorized into nine clusters, in which VI and VIII were apparently up-regulated under low relative soil moisture content (RSMC) level. The majority of genes in these two clusters was relevant to abiotic stress responses in abscisic acid (ABA) dependent and independent signaling pathway, including NCED, PYR/PYL/RCAR, SnRK2, ABF, MYB/MYC, AP2/ERF family, LEA and DHN. In contrast, genes within clusters II and IV were generally down-regulated under water stress; cluster IX genes were up-regulated during water recovery response to both low and high RSMC levels. Genes in implicated in tetrapyrrole binding, photosystem and photosynthetic membrane were the most affected in cluster IX. CONCLUSION: Taken together, our findings indicate that the responses of hulless barley to drought stress shows differences in the pathways and genes activated. Furthermore, all these genes displayed different sensitivities to soil water deficit and might be profitable for future drought tolerance improvement in barley and other crops.

Transcriptome sequencing in a Tibetan barley landrace with high resistance to powdery mildew.

Hulless barley is an important cereal crop worldwide, especially in Tibet of China. However, this crop is usually susceptible to powdery mildew caused by Blumeria graminis f. sp. hordei. In this study, we aimed to understand the functions and pathways of genes involved in the disease resistance by transcriptome sequencing of a Tibetan barley landrace with high resistance to powdery mildew. A total of 831 significant differentially expressed genes were found in the infected seedlings, covering 19 functions. Either "cell," "cell part," and "extracellular region" in the cellular component category or "binding" and "catalytic" in the category of molecular function as well as "metabolic process" and "cellular process" in the biological process category together demonstrated that these functions may be involved in the resistance to powdery mildew of the hulless barley. In addition, 330 KEGG pathways were found using BLASTx with an E-value cut-off of <10(-5). Among them, three pathways, namely, "photosynthesis," "plant-pathogen interaction," and "photosynthesis-antenna proteins" had significant matches in the database. Significant expressions of the three pathways were detected at 24 h, 48 h, and 96 h after infection, respectively. These results indicated a complex process of barley response to powdery mildew infection.

Integrated Transcriptomics and Metabolomics Analyses Provide Insights into Qingke in Response to Cold Stress.

The survival and productivity of qingke in high altitude (>4300 m, average yearly temperature <0 °C) of the Tibetan Plateau are significantly impacted by low-temperature stress. Uncovering the mechanisms underlying low-temperature stress response in cold-tolerant qingke varieties is crucial for qingke breeding. Herein, we conducted a comprehensive transcriptomic and metabolomic analysis on cold-sensitive (ZQ) and cold-tolerant (XL) qingke varieties under chilling and freezing treatments and identified lipid metabolism pathways as enriched in response to freezing treatment. Additionally, a significant positive correlation was observed between the expression of C-repeat (CRT) binding factor 10A (HvCBF10A) and Gly-Asp-Ser-Leu-motif lipase (HvGDSL) and the accumulation of multiple lipids. Functional analysis confirmed that HvCBF10A directly binds to HvGDSL, and silencing HvCBF10A resulted in a significant decrease in both HvGDSL and lipid levels, consequently impairing the cold tolerance. Overall, HvCBF10A and HvGDSL are functional units in actively regulating lipid metabolism to enhance freezing stress tolerance in qingke.

Extraction and characterization of waxy and normal barley ß-glucans and their effects on waxy and normal barley starch pasting and degradation properties and mash filtration rate.

Interactions between ß-glucan and starch influence the health benefits of barley-based foods and barley brewing performance. Here, we characterized ß-glucans from waxy and normal barley varieties and compared the effects of different ß-glucans on the pasting and degradation of waxy and normal barley starches as well as the filterability of mashes from unmalted waxy and normal barley. Waxy barley Zangqing18 ß-glucan displayed more compact micrographic features, higher molecular weight, larger particle size, higher thermal decomposition temperature and lower rheological viscosity than normal barley Zangqing2000 ß-glucan. ß-Glucan not only significantly decreased the pasting viscosities of waxy and normal starches but also lowered the pasting temperatures and peak times of normal starch, likely by inhibiting granule swelling and disrupting the integrity of the continuous phase. ß-Glucan also decreased in vitro digestion extent of starch and increased the resistant starch. The unmalted waxy barley had a mash filtration rate much faster than normal barley because starch and ß-glucan in waxy barley were rapidly and completely digested and formed more open filter passages. The effects of ß-glucan on starch properties varied with the types and contents of ß-glucans, whilst the types of starches showed more significant effects. CHEMICAL COMPOUNDS STUDIED: ß-Glucan (Pubchem CID: 439262); Amylopectin (Pubchem CID: 439207); Starch (Pubchem CID: 156595876).

Genome diversity and highland-adaptative variation in Tibet barley landrace population of China.

Barley landraces accumulated variation in adapting to extreme highland environments during long-term domestication in Tibet, but little is known about their population structure and genomic selection traces. In this study, tGBS (tunable genotyping by sequencing) sequencing, molecular marker and phenotypic analyses were conducted on 1,308 highland and 58 inland barley landraces in China. The accessions were divided into six sub-populations and clearly distinguished most six-rowed, naked barley accessions (Qingke in Tibet) from inland barley. Genome-wide differentiation was observed in all five sub-populations of Qingke and inland barley accessions. High genetic differentiation in the pericentric regions of chromosomes 2H and 3H contributed to formation of five types of Qingke. Ten haplotypes of the pericentric regions of 2H, 3H, 6H and 7H were further identified as associated with ecological diversification of these sub-populations. There was genetic exchange between eastern and western Qingke but they shared the same progenitor. The identification of 20 inland barley types indicated multiple origins of Qingke in Tibet. The distribution of the five types of Qingke corresponded to specific environments. Two predominant highland-adaptative variations were identified for low temperature tolerance and grain color. Our results provide new insights into the origin, genome differentiation, population structure and highland adaptation in highland barley which will benefit both germplasm enhancement and breeding of naked barley.

Quantitative Proteomics Analysis Reveals Proteins Associated with High Melatonin Content in Barley Seeds under NaCl-Induced Salt Stress.

Soil salinization limits hull-less barley cultivation in the Qinghai-Tibet Plateau of China. However, some wild hull-less barley seeds accumulate high melatonin (MEL) during germination with improved salt tolerance; but the mechanism of melatonin-mediated salt tolerance in hull-less barley is not well understood at the protein level. This study investigated proteome changes resulting in high melatonin content in germinating hull-less barley seeds under high saline conditions. The proteome profiles of seed treatment with 240 mM-NaCl (N), water (H), and control (C) taken 7 days after germination were compared using the TMT-based quantitative proteomics. Our results indicate that salt stress-induced global changes in the proteomes of germinating hull-less barley seeds, altering the expression and abundance of proteins related to cell cycle and control, carbohydrate and energy metabolism, and amino acid transport and metabolism including proteins related to melatonin production. Furthermore, proteins associated with cellular redox homeostasis, osmotic stress response, and secondary metabolites derived primarily from amino acid metabolism, purine degradation, and shikimate pathways increased significantly in abundance and may contribute to the high melatonin content in seeds under salt stress. Consequently, triggering the robust response to oxidative stress occasioned by the NaCl-induced salt stress, improved seed germination and strong adaptation to salt stress.

Genetic architecture of inducible and constitutive metabolic profile related to drought resistance in qingke (Tibetan hulless barley).

Qingke (Tibetan hulless barley, Hordeum vulgare L. var. nudum) is the primary food crop on the Tibet Plateau, the long-term drought and other harsh environments makes qingke an important resource for the study of abiotic resistance. Here, we evaluated the drought sensitivity of 246 qingke varieties. Genome-wide association studies (GWAS) found that root-specific expressed gene CYP84 may be involved in the regulation of drought resistance. Based on widely targeted metabolic profiling, we identified 2,769 metabolites in qingke leaves, of which 302 were significantly changed in response to drought stress, including 4-aminobutyric acid (GABA), proline, sucrose and raffinose. Unexpectedly, these drought-induced metabolites changed more violently in drought-sensitive qingkes, while the constitutive metabolites that had little response to drought stress, such as C-glycosylflavonoids and some amino acids, accumulated excessively in drought-resistant qingkes. Combined with metabolite-based genome-wide association study (mGWAS), a total of 1,006 metabolites under optimal condition and 1,031 metabolites under mild drought stress had significant associated loci. As a marker metabolite induced by drought stress, raffinose was significantly associated with two conservatively adjacent α-galactosidase genes, qRT-PCR suggests that these two genes may jointly regulate the raffinose content in qingke. Besides, as constituent metabolites with stable differences between drought-sensitive and drought-resistant qingkes, a class of C-glycosylflavonoids are simultaneously regulated by a UDP-glucosyltransferase gene. Overall, we performed GWAS for sensitivity and widely targeted metabolites during drought stress in qingke for the first time, which provides new insights into the response mechanism of plant drought stress and drought resistance breeding.

Resistance to Powdery Mildew in Qingke Involves the Accumulation of Aromatic Phenolamides Through Jasmonate-Mediated Activation of Defense-Related Genes.

Powdery mildew (PM) leads to severe yield reduction in qingke (Hordeum vulgare L. var. nudum). Although studies have focused on identifying PM-related resistance genes, mechanistic insights into the metabolic regulation networks of resistance against PM have rarely been explored in qingke. Here, we integrated transcriptomic, proteomic and metabolomic data using PM-susceptible (G72) and PM-resistant (K69) accessions to systemically explore the mechanisms of PM resistance. The integrated results show that a rapidly transduction of jasmonic acid (JA) and (+)-7-iso-jasmonoyl-L-isoleucine (JA-Ile), and importantly, a inducing accumulation of aromatic PAs conferred qingke-specific resistance for PM stress. Functional analysis revealed that the four BAHD N-acyltransferase genes were responsible for the synthesis of aliphatic and aromatic PAs. The expression of the four genes are induced by methyl jasmonate (MeJA) and PM treatment. Co-expression network analysis shows that a histone lysine demethylase, JMJ705 gene, also induced by MeJA and PM treatment, had highly correlation with PAs biosynthesis. Chromatin immunoprecipitation (ChIP)-seq assays revealed that the level of trimethylated histone H3 lysine 27 (H3K27me3) of the four genes in MeJA and PM-treated plants was significantly reduced. Overall, our results suggest that a novel strategy for jasmonic acid signal-mediated demethylation controlling the accumulation of aromatic PAs to enhance plant immune resistance through removal of H3K27me3 and activating defense-related gene expression.

Integrative metabolomic and transcriptomic analyses reveal the mechanisms of Tibetan hulless barley grain coloration.

Cereal grains accumulate anthocyanin during developmental process. The anthocyanin content increases at grain filling stages to develop grain coloration in cereals. However, anthocyanin biosynthesis responsible for grain coloring and its regulatory mechanisms controlled by structural and functional genes remain unclear. Therefore, this study aimed to explore the global map of metabolic changes linked to grain coloration of Tibetan hulless barley (qingke) using an integrative metabolome and transcriptome approach. Grains from three colored qingke cultivars at different developmental stages were considered for molecular and metabolic investigations. A total of 120 differentially accumulated metabolites (DAMs) and 8,327 differentially expressed genes (DEGs) were filtered. DEGs were mainly enriched in the phenylpropanoid and flavonoid pathways. The transcript levels of anthocyanin biosynthesis genes (PAL, C4H, 4CL, CHS, FLS, F3H, F3'H, DFR, ANS, GT, OMT, and MAT) significantly upregulate in colored qingke compared to the non-colored variety. During grain development and maturation, the strong correlation of HvMYC2 expression with anthocyanin contents and anthocyanin biosynthesis genes suggested it as a critical gene in anthocyanin accumulation. Further results confirmed that HvMYC2 could be activated by HvMYB and be a positive regulator of UV-B and cold tolerance in qingke. In addition, verification based on enzymatic assays indicated that six key modifier enzymes could catalyze glycosylation, malonylation, and methylation of anthocyanins, thereby dissecting the major anthocyanin modification pathway in colored qingke. Overall, our study provides global insight into anthocyanin accumulation and the mechanism underlying grain coloration in qingke.

Effects of Two Starch Synthase IIa Isoforms on Grain Components and Other Grain Traits in Barley.

Starch biosynthesis in cereal crops is a complex pathway regulated by multiple starch synthetic enzymes. Starch synthase IIa (SSIIa) is well-known to be one of the major starch synthases and is very important in amylopectin biosynthesis. It has significant effects on grain composition and kernel traits. However, there are few reports on the association of natural variation of SSIIa in barley and grain composition and characteristics. In this work, two SSIIa isoforms were first identified as SSIIaH and SSIIaL by one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis, mass spectrometry, and Western blotting. Sequence analysis of the SSIIa gene demonstrated that a 33 bp insertion coding a peptide of APPSSVVPAKK caused different SSIIa, e.g., SSIIaH and SSIIaL. Based on this molecular difference, a polymerase chain reaction marker was developed, which could be used to screen different SSIIa genotypes easily. Kernel hardness of SSIIaL genotypes was significantly higher than that of SSIIaH Chinese barley cultivars. The proportion of SSIIaL genotypes was extremely low in Australian barley cultivars (5/24) and much higher in Tibetan hull-less barley cultivars (46/74), consistent with the end-use requirements of barley grain. This study provided new information in barley endosperm starch synthesis and indicated that it is valuable for choosing the preferred SSIIa genotype according to the end-use requirements.

Drought Resistance in Qingke Involves a Reprogramming of the Phenylpropanoid Pathway and UDP-Glucosyltransferase Regulation of Abiotic Stress Tolerance Targeting Flavonoid Biosynthesis.

Tibetan hulless barley (qingke) is an important food crop in the Tibetan plateau. However, it often suffers from drought stress resulting in reduction of food production because of the extreme plateau environment. To elucidate the molecular mechanisms underlying the drought resistance of qingke, the transcriptomic and metabolomic responses of drought-sensitive (D) and drought-resistant (XL) accessions were characterized in experiments with a time course design. The phenylpropanoid pathway was reprogrammed by downregulating the lignin pathway and increasing the biosynthesis of flavonoids and anthocyanins, and this regulation improved plant tolerance for drought stress. Besides, flavonoid glycosides have induced accumulation of metabolites that participated in drought stress resistance. HVUL7H11410 exhibited the activity of wide-spectrum glucosyltransferase and mediated flavonoid glycosylation to enhance drought stress resistance. Overall, the findings provide insights into the regulatory mechanism underlying drought stress tolerance associated with metabolic reprogramming. Furthermore, the flavonoid-enriched qingke is more tolerant to drought stress and can be used as a functional food to benefit human health.

Quantitative Proteome Profiling Provides Insight into the Proteins Associated with ß-Glucan Accumulation in Hull-less Barley Grains.

The hull-less barley (Qingke) is widely planted as a staple food crop in the Tibetan area, China, and the grains contains high content of ß-glucan (BG). The mechanisms of BG synthesis and accumulation in qingke has not been studied at the protein level. This study characterized the proteins associated with BG synthesis and accumulation during qingke seed development. The proteome profiles of qingke seeds taken at 20, 30, and 40 days after flowering were compared using the TMT-based quantitative proteomics. A total of 4283 proteins were identified, with 759 being differentially expressed (DEPs) throughout seed development. Comparisons of protein expression pattern, functions, and pathway enrichment tests highlight cell wall modification, carbon and energy metabolism, polysaccharide metabolism, post-transcriptional modifications, and vesicular transport as critical biological processes related to qingke BG accumulation. Furthermore, induction of starch synthase, starch branching enzyme, pectin acetyl esterases, beta-glucosidases, beta-amylases, 1,4-beta-xylan, xyloglucan, α-amylase inhibitors, and glycosyltransferases underpinned BG synthesis. The results also indicated that the proteins involved in glycolytic, gluconeogenesis, and glyoxylate bypass pathways provided energy and reducing power for BG storage. Parallel reaction monitoring (PRM) and quantitative real-time PCR (qPCR) analyses confirmed the expression profile of the proteins obtained by TMT-based proteomics. The current results provided an insight into the mechanisms of BG synthesis and accumulation during qingke seed development.

Comparative proteomics analysis of Tibetan hull-less barley under osmotic stress via data-independent acquisition mass spectrometry.

BACKGROUND: Tibetan hull-less barley (Hordeum vulgare L. var. nudum) is one of the primary crops cultivated in the mountains of Tibet and encounters low temperature, high salinity, and drought. Specifically, drought is one of the major abiotic stresses that affect and limit Tibetan barley growth. Osmotic stress is often simultaneously accompanied by drought conditions. Thus, to improve crop yield, it is critical to explore the molecular mechanism governing the responses of hull-less barley to osmotic/drought stress conditions. FINDINGS: In this study, we used quantitative proteomics by data-independent acquisition mass spectrometry to investigate protein abundance changes in tolerant (XL) and sensitive (DQ) cultivars. A total of 6,921 proteins were identified and quantified in all samples. Two distinct strategies based on pairwise and time-course comparisons were utilized in the comprehensive analysis of differentially abundant proteins. Further functional analysis of differentially abundant proteins revealed that some hormone metabolism-associated and phytohormone abscisic acid-induced genes are primarily affected by osmotic stress. Enhanced regulation of reactive oxygen species (may promote the tolerance of hull-less barley under osmotic stress. Moreover, we found that some regulators, such as GRF, PR10, MAPK, and AMPK, were centrally positioned in the gene regulatory network, suggesting that they may have a dominant role in the osmotic stress response of Tibetan barley. CONCLUSIONS: Our findings highlight a subset of proteins and processes that are involved in the alleviation of osmotic stress. In addition, this study provides a large-scale and multidimensional proteomic data resource for the further investigation and improvement of osmotic/drought stress tolerance in hull-less barley or other plant species.

Effects of the addition of waxy and normal hull-less barley flours on the farinograph and pasting properties of composite flours and on the nutritional value, textural qualities, and in vitro digestibility of resultant breads.

Hull-less barley (HLB), especially waxy HLB, contains many physiologically active ingredients; however, its poor processing performance and end-product quality are unfavorable. In this study, 80% waxy or normal HLB wholegrain flour (WGF) and 20% wheat flour were used for baking bread. The farinograph and pasting properties of composite powders, and the nutritional value, textural properties, and in vitro hydrolysis of resultant breads were evaluated. The addition of a high proportion of HLB WGFs significantly increased the nutritional value of breads, especially the ß-glucan contents of waxy HLB breads. The addition of HLB WGFs and a suitable amount of wheat gluten led to a lower degree of softening of HLB bread flours but improved its farinograph characteristics, such as higher water absorption rate, development time, stability time, and farinograph quality number. Although the sensory profiles of HLB breads were considerably lower than those of wheat bread, they still received a good overall acceptability from a panel of sensory evaluators. HLB breads, particularly the waxy types, exhibited higher hardness, gumminess, chewiness, and lower specific volume, glycemic index and equilibrium concentration in starch hydrolysis. After baking, the starch crystallinity of dough changed from A to V type, and the relative crystallinity decreased. Overall, waxy HLB breads had more nutritional value than normal HLB breads. Higher ß-glucan and total dietary fiber content in HLB might have a positive effect on the nutritional value of the resultant breads. However, high ß-glucan and total dietary fiber was also accompanied by a negative effect on the sensory quality and processing performance of the end product. PRACTICAL APPLICATION: The composite flour with 80 g hull-less barley wholegrain flour, 20 g wheat flour, and 30 g wheat gluten can be substituted in breadmaking. Compared to wheat bread, hull-less barley bread exhibited different but acceptable sensory properties and had more nutritional value, particularly the waxy one. Therefore, a high proportion of hull-less barley could be recommended for bread production.

An improved high-quality genome assembly and annotation of Tibetan hulless barley.

Hulless barley (Hordeum vulgare L. var. nudum) is a barley variety that has loose husk cover of the caryopses. Because of the ease in processing and edibility, hulless barley has been locally cultivated and used as human food. For example, in Tibetan Plateau, hulless barley is the staple food for human and essential livestock feed. Although the draft genome of hulless barley has been sequenced, the assembly remains fragmented. Here, we reported an improved high-quality assembly and annotation of the Tibetan hulless barley genome using more than 67X PacBio long-reads. The N50 contig length of the new assembly is at least more than 19 times larger than other available barley assemblies. The new genome assembly also showed high gene completeness and high collinearity of genome synteny with the previously reported barley genome. The new genome assembly and annotation will not only remove major hurdles in genetic analysis and breeding of hulless barley, but will also serve as a key resource for studying barley genomics and genetics.