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Our previous studies showed that high salt tolerance in Tibetan wild barley accessions was associated with HvHKT1;1, a member of the high-affinity potassium transporter family. However, molecular mechanisms of HvHKT1;1 for salt tolerance and its roles in K+/Na+ homeostasis remain to be elucidated. Functional characterization of HvHKT1;1 was conducted in the present study. NaCl-induced transcripts of HvHKT1;1 were significantly higher in the roots of Tibetan wild barley XZ16 relative to other genotypes, being closely associated with its higher biomass and lower tissue Na+ content under salt stress. Heterologous expression of HvHKT1;1 in Saccharomyces cerevisiae (yeast) and Xenopus laevis oocytes showed that HvHKT1;1 had higher selectivity for Na+ over K+ and other monovalent cations. HvHKT1;1 was found to be localized at the cell plasma membrane of root stele and epidermis. Knock-down of HvHKT1;1 in barley led to higher Na+ accumulation in both roots and leaves, while overexpression of HvHKT1;1 in salt-sensitive Arabidopsis hkt1-4 and sos1-12 loss-of-function lines resulted in significantly less shoot and root Na+ accumulation. Additionally, microelectrode ion flux measurements and root elongation assay revealed that the transgenic Arabidopsis plants exhibited a remarkable capacity for regulation of Na+, K+, Ca2+ and H+ homeostasis under salt stress. These results indicate that HvHKT1;1 is critical in radial root Na+ transport, which eventually reduces shoot Na+ accumulation. Additionally, HvHKT1;1 may be indirectly involved in retention of K+ and Ca2+ in root cells, which also improves plant salt tolerance. [ABSTRACT FROM AUTHOR]

Summary: Qingke, the local name of hulless barley in the Tibetan Plateau, is a staple food for Tibetans. The availability of its reference genome sequences could be useful for studies on breeding and molecular evolution. Taking advantage of the third‐generation sequencer (PacBio), we de novo assembled a 4.84‐Gb genome sequence of qingke, cv. Zangqing320 and anchored a 4.59‐Gb sequence to seven chromosomes. Of the 46,787 annotated ‘high‐confidence’ genes, 31 564 were validated by RNA‐sequencing data of 39 wild and cultivated barley genotypes with wide genetic diversity, and the results were also confirmed by nonredundant protein database from NCBI. As some gaps in the reference genome of Morex were covered in the reference genome of Zangqing320 by PacBio reads, we believe that the Zangqing320 genome provides the useful supplements for the Morex genome. Using the qingke genome as a reference, we conducted a genome comparison, revealing a close genetic relationship between a hulled barley (cv. Morex) and a hulless barley (cv. Zangqing320), which is strongly supported by the low‐diversity regions in the two genomes. Considering the origin of Morex from its breeding pedigree, we then demonstrated a close genomic relationship between modern cultivated barley and qingke. Given this genomic relationship and the large genetic diversity between qingke and modern cultivated barley, we propose that qingke could provide elite genes for barley improvement. [ABSTRACT FROM AUTHOR]

Summary: Pseudogenes have a reputation of being ‘evolutionary relics’ or ‘junk DNA’. While they are well characterized in mammals, studies in more complex plant genomes have so far been hampered by the absence of reference genome sequences. Barley is one of the economically most important cereals and has a genome size of 5.1 Gb. With the first high‐quality genome reference assembly available for a Triticeae crop, we conducted a whole‐genome assessment of pseudogenes on the barley genome. We identified, characterized and classified 89 440 gene fragments and pseudogenes scattered along the chromosomes, with occasional hotspots and higher densities at the chromosome ends. Full‐length pseudogenes (11 015) have preferentially retained their exon–intron structure. Retrotransposition of processed mRNAs only plays a marginal role in their creation. However, the distribution of retroposed pseudogenes reflects the Rabl configuration of barley chromosomes and thus hints at founding mechanisms. While parent genes related to the defense‐response were found to be under‐represented in cultivated barley, we detected several defense‐related pseudogenes in wild barley accessions. The percentage of transcriptionally active pseudogenes is 7.2%, and these may potentially adopt new regulatory roles.The barley genome is rich in pseudogenes and small gene fragments mainly located towards chromosome tips or as tandemly repeated units. Our results indicate non‐random duplication and pseudogenization preferences and improve our understanding of the dynamics of gene birth and death in large plant genomes and the mechanisms that lead to evolutionary innovations. [ABSTRACT FROM AUTHOR]

Cobalt (Co) is beneficial for legume plants and not an essential element for most plants. There is no sufficient information about the effect of Co stress on barley growth. The current experiment was carried out to investigate the effects of different Co levels (25, 50, 75, and 100 µM) on growth and physiological traits of three barley genotypes (B325, J36, and B340) differing in Co tolerance. The results showed that Co stress inhibited plant growth, decreased chlorophyll content and photosynthetic rate, and enhanced oxidative stress. However, the effects differed among genotypes, with B325 and B340 being the most and the least affected, respectively. Co stress caused decrease and increase of manganese (Mn) and phosphorus (P) concentrations in both roots and shoots, respectively; iron (Fe) concentration had little change in shoots and a significant decrease in roots. The current results showed a close association of Co tolerance and its accumulation in plant tissues. [ABSTRACT FROM PUBLISHER]

Purple grains in barley are caused by the presence of anthocyanin in both aleurone and pericarp, and the trait is controlled by one or two dominant genes. In this study, we demonstrated that purple grain was controlled by a single dominant gene using reciprocal crosses between Yuyaohongdamai and AC Parkhill or ACCA. The close linkage between grain color and spike type (controlled by Vrs1) was found in the crosses between Yuyaohongdamai and ACCA. The purple-grain gene was mapped on chromosome 2HL between the SSR markers Bmag0125 (1.2 cM) and GBMS244 (2.8 cM), and was about 5.1 cM distal from Vrs1. The marker enrichment in the target region was carried out by amplifying barley EST- and rice homologous gene-based searching for polymorphic loci adjacent to Pre2. Four of the newly developed markers were mapped in the Pre2 gene region. The purple lemma and pericarp gene ( Pre2) was then finely mapped between InDel marker PQJ1056 (from EST BM096525) and HvOs04g47170 with genetic distance of 0.3 and 0.1 cM, respectively. [ABSTRACT FROM AUTHOR]

Potassium (K) deficiency is one of the major factors affecting crop growth and productivity. Development of low-K tolerant crops is an effective approach to solve the nutritional deficiency in agricultural production. Tibetan annual wild barley is rich in genetic diversity and can grow normally under poor soils, including low-K supply. However, the molecular mechanism about low K tolerance is still poorly understood. In this study, Illumina RNA-Sequencing was performed using two Tibetan wild barley genotypes differing in low K tolerance (XZ153, tolerant and XZ141, sensitive), to determine the genotypic difference in transcriptome profiling. We identified a total of 692 differentially expressed genes (DEGs) in two genotypes at 6 h and 48 h after low-K treatment, including transcription factors, transporters and kinases, oxidative stress and hormone signaling related genes. Meanwhile, 294 low-K tolerant associated DEGs were assigned to transporter and antioxidant activities, stimulus response, and other gene ontology (GO), which were mainly involved in starch and sucrose metabolism, lipid metabolism and ethylene biosynthesis. Finally, a hypothetical model of low-K tolerance mechanism in XZ153 was presented. It may be concluded that wild barley accession XZ153 has a higher capability of K absorption and use efficiency than XZ141 under low K stress. A rapid response to low K stress in XZ153 is attributed to its more K uptake and accumulation in plants, resulting in higher low K tolerance. The ethylene response pathway may account for the genotypic difference in low-K tolerance. [ABSTRACT FROM AUTHOR]

Tibetan annual wild barley is rich in genetic variation. This study was aimed at the exploitation of new SSRs for the genetic diversity and phylogenetic analysis of wild barley by data mining. We developed 49 novel EST-SSRs and confirmed 20 genomic SSRs for 80 Tibetan annual wild barley and 16 cultivated barley accessions. A total of 213 alleles were generated from 69 loci with an average of 3.14 alleles per locus. The trimeric repeats were the most abundant motifs (40.82%) among the EST-SSRs, while the majority of the genomic SSRs were di-nuleotide repeats. The polymorphic information content (PIC) ranged from 0.08 to 0.75 with a mean of 0.46. Besides this, the expected heterozygosity (He) ranged from 0.0854 to 0.7842 with an average of 0.5279. Overall, the polymorphism of genomic SSRs was higher than that of EST-SSRs. Furthermore, the number of alleles and the PIC of wild barley were both higher than that of cultivated barley, being 3.12 vs 2.59 and 0.44 vs 0.37. Indicating more polymorphism existed in the Tibetan wild barley than in cultivated barley. The 96 accessions were divided into eight subpopulations based on 69 SSR markers, and the cultivated genotypes can be clearly separated from wild barleys. A total of 47 SSR-containing EST unigenes showed significant similarities to the known genes. These EST-SSR markers have potential for application in germplasm appraisal, genetic diversity and population structure analysis, facilitating marker-assisted breeding and crop improvement in barley. [ABSTRACT FROM AUTHOR]

To reveal grain physio-chemical and proteomic differences between two barley genotypes, Zhenong8 and W6nk2 of high- and low- grain-Cd-accumulation, grain profiles of ultrastructure, amino acid and proteins were compared. Results showed that W6nk2 possesses significantly lower protein content, with hordein depicting the greatest genotypic difference, compared with Zhenong8, and lower amino acid contents with especially lower proportion of Glu, Tyr, Phe and Pro. Both scanning and transmission electron microscopy observation declared that the size of A-type starch molecule in W6nk2 was considerably larger than that of Zhenong8. Grains of Zhenong8 exhibited more protein-rich deposits around starch granules, with some A-type granules having surface pits. Seventeen proteins were identified in grains, using 2-DE coupled with mass spectrometry, with higher expression in Zhenong8 than that in W6nk2; including z-type serpin, serpin-Z7 and alpha-amylase/trypsin inhibitor CM, carbohydrate metabolism, protein synthesis and signal transduction related proteins. Twelve proteins were less expressed in Zhenong8 than that in W6nk2; including barley trypsin inhibitor chloroform/methanol-soluble protein (BTI-CMe2.1, BTI-CMe2.2), trypsin inhibitor, dehydroascorbate reductase (DHAR), pericentrin, dynein heavy chain and some antiviral related proteins. The data extend our understanding of mechanisms underlying Cd accumulation/tolerance and provides possible utilization of elite genetic resources in developing low-grain-Cd barley cultivars. [ABSTRACT FROM AUTHOR]

Aluminum (Al) toxicity is a major limiting factor for plant production in acid soils. Wild barley germplasm is rich in genetic diversity and may provide elite genes for crop Al tolerance improvement. The hydroponic-experiments were performed to compare proteomic and transcriptional characteristics of two contrasting Tibetan wild barley genotypes Al- resistant/tolerant XZ16 and Al-sensitive XZ61 as well as Al-resistant cv. Dayton. Results showed that XZ16 had less Al uptake and translocation than XZ61 and Dayton under Al stress. Thirty-five Al-tolerance/resistance-associated proteins were identified and categorized mainly in metabolism, energy, cell growth/division, protein biosynthesis, protein destination/storage, transporter, signal transduction, disease/defense, etc. Among them, 30 were mapped on barley genome, with 16 proteins being exclusively up-regulated by Al stress in XZ16, including 4 proteins (S-adenosylmethionine-synthase 3, ATP synthase beta subunit, triosephosphate isomerase, Bp2A) specifically expressed in XZ16 but not Dayton. The findings highlighted the significance of specific-proteins associated with Al tolerance, and verified Tibetan wild barley as a novel genetic resource for Al tolerance. [ABSTRACT FROM AUTHOR]

Tibetan wild barley is rich in genetic diversity with potential allelic variation useful for salinity-tolerant improvement of the crop. The objectives of this study were to evaluate salinity tolerance and analysis of the allelic function of HvHKT1 and HvHKT2 in Tibetan wild barley. Salinity tolerance of 189 Tibetan wild barley accessions was evaluated in terms of reduced dry biomass under salinity stress. In addition, Na and K concentrations of 48 representative accessions differing in salinity tolerance were determined. Furthermore, the allelic and functional diversity of HvHKT1 and HvHKT2 was determined by association analysis as well as gene expression assay. There was a wide variation among wild barley genotypes in salt tolerance, with some accessions being higher in tolerance than cultivated barley CM 72, and salinity tolerance was significantly associated with K/Na ratio. Association analysis revealed that HvHKT1 and HvHKT2 mainly control Na and K transporting under salinity stress, respectively, which was validated by further analysis of gene expression. The present results indicated that Tibetan wild barley offers elite alleles of HvHKT1 and HvHKT2 conferring salinity tolerance. [ABSTRACT FROM AUTHOR]

greenhouse hydroponic experiment was performed using Cd-sensitive (cv. Dong 17) and Cd-tolerant (Weisuobuzhi) barley seedlings to evaluate how different genotypes responded to cadmium (Cd) toxicity in the presence of sodium nitroprusside (SNP), a nitric oxide (NO) donor. Results showed that 5 μM Cd increased the accumulation of O, HO, and malondialdehyde (MDA) but reduced plant height, chlorophyll content, net photosynthetic rate ( P), and biomass, with a much more severe response in the Cd-sensitive genotype. Antioxidant enzyme activities increased significantly under Cd stress in the roots of the tolerant genotype, whereas in leaves of the sensitive genotype, superoxide dismutase (SOD) and ascorbate peroxide (APX), especially cytosol ascorbate peroxidase (cAPX), decreased after 5-15 days Cd exposure. Moreover, Cd induces NO synthesis by stimulating nitrate reductase and nitric oxide synthetase-like enzymes in roots/leaves. A Cd-induced NO transient increase in roots of the Cd-tolerant genotype might partly contribute to its Cd tolerance. Exogenous NO dramatically alleviated Cd toxicity, markedly diminished Cd-induced reactive oxygen species (ROS) and MDA accumulation, ameliorated Cd-induced damage to leaf/root ultrastructure, and increased chlorophyll content and P. External NO counteracted the pattern of alterations in certain antioxidant enzymes induced by Cd; for example, it significantly elevated the depressed SOD, APX, and catalase (CAT) activities in the Cd-sensitive genotype after 10- and 15-day treatments. Furthermore, NO significantly increased stromal APX and Mn-SOD activities in both genotypes and upregulated Cd-induced decrease in cAPX activity and gene expression of root/leaf cAPX and leaf CAT1 in the Cd-sensitive genotype. These data suggest that under Cd stress, NO, as a potent antioxidant, protects barley seedlings against oxidative damage by directly and indirectly scavenging ROS and helps to maintain stability and integrity of the subcellular structure. [ABSTRACT FROM AUTHOR]

Heading date (HD) is an important agronomic trait that influences plant adaptability to varying environment and, ultimately, grain yield. In this study, two doubled haploid (DH) populations were used to identify new QTL for HD. One of the DH populations is originated from a cross between an Australian malting barley cv. Franklin and a wild barley accession TAM407227 and the other one is from the cross between a Syrian wild barley SYR01 and an Australian malting barley cv. Gairdner. Using three times of sowing (TOS) differing in daylength and temperature, we investigated quantitative trait loci (QTL) controlling HD from both populations. Fourteen QTL were identified for HD from different populations and sowing dates. The expression of HD related genes varied with the TOS, suggesting a significant QTL × environment interaction. By comparing the positions of previously mapped HD genes and those of QTL detected in this population, we found that eleven of the fourteen QTL identified in this study were located at similar positions to those reported genes for HD. Among the three new potential QTL, one was located at 73.5 cM on chromosome 2H, explaining 19.2% and 4.6% HD of DH lines in spring and summer growing, respectively. The wild barley parent TAM407227 contributed the early maturity allele. HORVU2Hr1G088460 within the interval of QTL could be the candidate gene. The second new QTL was identified on chromosome 3H from a summer sowing trial and the third one on chromosome 4H affected HD of DH lines only under spring sowing condition. These new QTL identified will provide alternative genetic resources for plant breeders developing barley varieties with improved HD adaptability to varying environments. [ABSTRACT FROM AUTHOR]

Limit dextrinase (LD) and limit dextrinase inhibitor (LDI) are the two important traits affecting malt quality. The genetic variation and controlling of LD activity and LDI content in barley grains and malt are not well understood. In this study, we measured LD activity and LDI content in both grains and malt of 68 cultivated barley genotypes. The results show that there is a wide difference among barley genotypes in both LD activity and LDI content. LD in malt is not correlated with LD in grains, but negatively correlated with LDI in malt. LD in malt is positively correlated with diastatic power (DP), Kolbach index (KI) and soluble nitrogen content (SN), and negatively correlated with viscosity (VC). LDI in malt is positively correlated with DP and total nitrogen (TN), and negatively correlated with KI. Association analysis identifies 5 QTLs associated with LD and 3 QTLs associated with LDI in malt. Three major QTLs controlling LD in malt account for 35.7%, 35.7% and 28.4% of phenotypic variation, respectively. A total of 17 QTLs associated with malt quality are identified. The current results address the importance of both LD and LDI in affecting malt quality and the identified QTLs could be useful in barley breeding. [ABSTRACT FROM AUTHOR]

Arsenic (As) is a ubiquitous metalloid and toxic to plants. Chemical similarity between arsenate and phosphate (P) indicates possible antagonism between them in uptake and transportation. However, there is little study to reveal the interaction of As and P at transcriptional level. In this study RNA-sequencing was conducted on the two barley genotypes differing in As tolerance. A total of 2942 differentially expressed genes (DEGs) were inclusively expressed in both genotypes under As (100 μM) and As (100 μM) + P (50 μM), and these DEGs included hormonal signaling, stress responsive, transport related and transcription factors. P addition in the culture solution inhibited the KEGG pathways related to ABC transporters, ether lipid metabolism, linolenic acid metabolism, endocytosis and RNA transport. ZDB160 had a higher expression of DEGs associated with hormone signaling, secondary metabolites and stress defense under P conditions compared to ZDB475, which might explain its tolerance mechanism to As under P condition. The abscisic acid, jasmonic acid and salicylic acid signaling pathways were also significantly regulated under As + P conditions, which may also account for genotypic differences. Finally we drew up a hypothetical model of high As + P stress tolerance mechanism in ZDB160. It may be concluded that ZDB160 achieves its tolerance to As under P by up-regulating P transporters, resulting in more P uptake and less As translocation. The identified candidate genes related to As + P tolerance may provide insights into understanding As tolerance under limited P conditions. [ABSTRACT FROM AUTHOR]

In a previous study, we identified the low-nitrogen (LN) tolerant accessions from the Tibetan wild barley ( Hordeum vulgare subsp. spontaneum ). In this study, two wild barley genotypes (XZ149, LN-tolerant and XZ56, LN-sensitive) and a barley cultivar ZD9 ( H. vulgare ) were used to determine the LN tolerant mechanism underlying the wild barley in the ionomic and physiological aspects. XZ149 exhibited higher LN tolerance with highest relative dry weight and N accumulation among three barley genotypes under LN stress. When exposed to LN stress, XZ149 had more N transportation from roots to leaves, and remained relatively higher activities of nitrate reductase (NR, EC.1.7.1.1) and glutamine synthetase (GS, EC.6.3.1.2) in leaves than other two genotypes, ensuring its higher capacity of N assimilation and utilization. The ionome analysis showed that LN stress had a significant effect on tissue ionome and the effect was genotypic and tissue-specific difference. On the whole, XZ149 maintained more stable Mn and Cu contents in roots, and less reduction of root P, K and Ca contents than XZ56 and ZD9 when exposed to LN stress. It may be assumed that more N movement into shoots, greater N assimilating capacity and specific rearrangement of nutrient element levels in tissues under LN stress are attributed to LN tolerance in XZ149. [ABSTRACT FROM AUTHOR]

Abstract: Greenhouse pot experiments were conducted to investigate genotypic differences in response to individual and combined stresses of drought and salinity between Tibetan wild barley genotypes (XZ5, drought-tolerant; XZ16, salinity/aluminum tolerant) and cv. CM72 (salinity-tolerant). Either drought (D) or salinity (S) alone and in combination (D + S) stresses significantly decreased plant growth, chlorophyll content, net photosynthetic rate (Pn), maximal photochemical efficiency of PSII (Fv/Fm), water potential and osmotic potential, with the largest suppression under combined stress, and two wild genotypes showing more tolerance than CM72. Water use efficiency (WUE) increased significantly in XZ5 and XZ16 after D + S, but no significant change in CM72. XZ5 and XZ16 showed 30.9% and 12.1% higher K+ level and 30.5% and 24.1% lower Na+/K+ ratio in plants, compared with CM72, with increased metal nutrients as Ca, Fe and Mn under D + S. The peak accumulation in proline and glycine-beatine was recorded in combined stress with larger accumulation in two wild genotypes. Moreover, larger increases in the level of ASA and GSH, and the activities of Ca2+Mg2+-ATPase, and superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), guaiacol peroxidase (POD) and glutathione reductase (GR) under D + S vs control were observed in XZ5 and XZ16 than CM72, with less accumulation of H2O2 and malondialdehyde. These results suggest that high tolerance to D + S stress of XZ5 and XZ16 is closely related to lower Na+/K+ ratio and enhanced Ca2+Mg2+-ATPase, proline, glycine-beatine and WUE, and improved capacity of antioxidative performance to scavenge reactive oxygen species and thus suppressed level of lipid peroxidation. [Copyright &y& Elsevier]

Abstract: Lipoxygenase (LOX) is a key factor affecting quality of beer in terms of foam stability and flavour. Low LOX content is a desirable trait for malting quality. A doubled haploid (DH) population was made from a cross of Australian malting barley Stirling and Canadian malting barley Harrington and mapped with 513 molecular markers. The 120 DH lines with their parents were planted in field trials and the harvested grains were micro-malted for analysis of LOX content in two consecutive years. LOX content was controlled by both genetic effects and environment conditions. Three QTLs were consistently detected. One QTL flanked by the markers E6216 and SCssr03907 at the telomere region of chromosome 5HL contributed 39% of genetic variation in LOX content. The second QTL close to the centromere region of chromosome 5H accounted for 17% of genetic variation. A minor QTL on chromosome 2H explained 6% of genetic variation but was significant in both years. The Australian variety Stirling contributed to higher LOX content for the three QTLs. The two QTLs mapped at chromosome 5H for LOX content coincided with the QTLs for seed dormancy/pre-harvest sprouting from the same population. The pre-harvest sprouting susceptible alleles were associated with low LOX content, which indicated that the low LOX QTL from the Canadian malting barleys are only useful in the barley growing areas where the pre-harvest sprouting risk is low. New genetic sources for low LOX should be exploited in different germplasm with different mechanisms. [Copyright &y& Elsevier]

Abstract: Improvement of malt quality is the most important objective in malt barley breeding. The current experiments investigated the variation of malt quality characters among barley genotypes and the difference in genetic variants of HvGlb1, encoding β-glucanase isoenzyme I, between Tibetan annual wild barley and cultivated barley. The correlation between the gene variants and malt quality showed that there was a large difference in the four malt quality parameters, i.e. Kolbach index, diastatic power (DP), viscosity and malt extract, among the analyzed barley cultivars. Kolbach index was negatively and positively correlated with viscosity and malt extract, respectively, while malt extract was negatively correlated with viscosity. Malt β-glucan content was a major determinant of malt quality, and was significantly correlated with Kolbach index (−0.633), malt extract (−0.333) and viscosity (0.672). On the other hand, malt β-glucan content was mainly controlled by malt β-glucanase activity. The correlation analysis showed that the HvGlb1 gene was correlated with malt β-glucan content and three of four main malt quality parameters, except DP. In addition, we also found that the HvGlb1 of Tibetan barley had wider diversity in haplotype than that of the cultivated barley, supporting the hypothesis that Tibet is one of the original centers of cultivated barley. [Copyright &y& Elsevier]

Abstract: Soil cadmium (Cd) contamination has posed a serious problem for safe food production and become a potential agricultural and environmental hazard worldwide. Greenhouse hydroponic experiments were conducted to investigate the modulation of exogenous GSH (reduced glutathione) in antioxidant defense system against the Cd-induced toxicity in plants exposed to 5 μM Cd using two barley genotypes differing in Cd tolerance. Addition of 20 mg L−1 GSH in 5 μM Cd culture medium significantly alleviated Cd-induced growth inhibition, especially for the sensitive genotype Dong 17 and dramatically depressed O2 −, H2O2 and malondialdehyde (MDA) accumulation. GSH mediated intracellular GSH content to keep the level over the control especially in the case of Cd-induced GSH reduction. External GSH counteracted Cd-induced alterations of certain antioxidant enzymes, e.g. brought root dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR) and glutathione peroxidase (GPX) activities of the both genotypes down towards the control level, but elevated the depressed ascorbate peroxidase (APX) and catalase (CAT) activities in Dong 17 after 10–15 d treatment. The examination of APX and superoxide dismutase (SOD) isoenzymes revealed GSH significantly increased MnSOD, sAPX and tAPX activities in the both genotypes, and strongly stimulated Cd-induced decrease in cAPX in the sensitive genotype. Furthermore, External GSH up-regulated root cAPX and leaf cAPX, CAT1, and CAT2 expression at transcript level in Dong 17 to achieve stimulation. These data, especially from the results of depressed O2 −, H2O2 and MDA accumulation and elevated Cd-induced decrease in GSH content and APX (strongly stimulated cAPX, sAPX and tAPX) and CAT activities by GSH addition in the sensitive genotype, suggest that elevated intracellular GSH and stimulated APX (especially cAPX, sAPX and tAPX iosenzymes) and CAT activities, when concerning ROS scavenging systems, play an important role in GSH-induced alleviation of oxidative stress. [Copyright &y& Elsevier]