Improved tolerance to various abiotic stresses in transgenic sweet potato (Ipomoea batatas) expressing spinach betaine aldehyde dehydrogenase

Abiotic stresses are critical delimiters for the increased productivity and cultivation expansion of sweet potato (Ipomoea batatas), a root crop with worldwide importance. The increased production of glycine betaine (GB) improves plant tolerance to various abiotic stresses without strong phenotypic changes, providing a feasible approach to improve stable yield production under unfavorable conditions. The gene encoding betaine aldehyde dehydrogenase (BADH) is involved in the biosynthesis of GB in plants, and the accumulation of GB by the heterologous overexpression of BADH improves abiotic stress tolerance in plants. This study is to improve sweet potato, a GB accumulator, resistant to multiple abiotic stresses by promoted GB biosynthesis. A chloroplastic BADH gene from Spinacia oleracea (SoBADH) was introduced into the sweet potato cultivar Sushu-2 via Agrobacterium-mediated transformation. The overexpression of SoBADH in the transgenic sweet potato improved tolerance to various abiotic stresses, including salt, oxidative stress, and low temperature. The increased BADH activity and GB accumulation in the transgenic plant lines under normal and multiple environmental stresses resulted in increased protection against cell damage through the maintenance of cell membrane integrity, stronger photosynthetic activity, reduced reactive oxygen species (ROS) production, and induction or activation of ROS scavenging by the increased activity of free radical-scavenging enzymes. The increased proline accumulation and systemic upregulation of many ROS-scavenging genes in stress-treated transgenic plants also indicated that GB accumulation might stimulate the ROS-scavenging system and proline biosynthesis via an integrative mechanism. This study demonstrates that the enhancement of GB biosynthesis in sweet potato is an effective and feasible approach to improve its tolerance to multiple abiotic stresses without causing phenotypic defects. This strategy for trait improvement in sweet potato not only stabilizes yield production in normal soils in unpredictable climates but also provides a novel germplasm for sweet potato production on marginal lands.     

UVA诱发的1O2和O2-·产生与脂质过氧化水平关系的研究

紫外A(UVA,320 nm-400 nm)诱发的脂质过氧化反应是通过活性氧(ROS)介导的。在UVA照射之后,单线态氧(1O2)和超氧阴离子(O2-.)是细胞内最初产生的ROS,它们进一步生成过氧化氢(H2O2),羟自由基(.OH)等其它自由基。为了探讨UVA照射后最早生成的1O2和O2-.与细胞氧化损伤后果的关系,我们采用一种特异性检测1O2和O2-.的高灵敏度化学发光探针MCLA(2-methyl-6-(4-methoxyphenyl)-3,7-dihydroimid-azo[1,2-α]pyrazin-3-one hydrochloride)检测人外周血淋巴细胞经UVA照射后的化学发光变化。发现不同剂量UVA照射后,细胞MCLA化学发光变化和MDA浓度变化一致。结果表明UVA照射后1O2和O2-.的水平与由此引发的脂质过氧化损伤存在正相关关系。因此,MCLA化学发光方法可望作为一种检测UVA诱发脂质过氧化水平的简单快速方法。     

Ectopic expression of GmPAP3 alleviates oxidative damage caused by salinity and osmotic stresses

The primary biochemical reaction of purple acid phosphatases (PAP) is to catalyze the hydrolysis of phosphate esters and anhydrides. However, the soybean GmPAP3 gene expression is induced by NaCl, osmotic, and oxidative treatments, indicating a possible role of PAP in abiotic stress responses. Confocal and electron microscopic studies demonstrated that GmPAP3 protein is mainly localized in mitochondria, a primary site for reactive oxygen species (ROS) production. When subjected to NaCl and polyethylene glycol (PEG) treatments, ectopic expression of GmPAP3 in transgenic tobacco BY-2 cells mimicked the protective effects exhibited by the antioxidant ascorbic acid: increase in the percentage of cells with active mitochondria; reduction in the percentage of dead cells; and reduced accumulation of ROS. In addition, when GmPAP3 transgenic Arabidopsis thaliana seedlings were subjected to NaCl, PEG, and paraquat (PQ) treatments, the percentage of root elongation was significantly higher than the wild type. Furthermore, PQ-induced lipid peroxidation in these transgenic seedlings was also reduced. In summary, the mitochondrial localized GmPAP3 may play a role in stress tolerance by enhancing ROS scavenging.     

Rapid monitoring of diabetes-induced lipid peroxidation by Fourier transform infrared spectroscopy: evidence from rat liver microsomal membranes

Increased oxidative stress is the consequence of either enhanced reactive oxygen species (ROS) production or attenuated ROS scavenging capacity, resulting in tissue damage that in most instances is assessed by the measurement of lipid peroxides. In the current study, diabetes-induced lipid peroxidation in rat liver microsomal membranes was investigated by Fourier transform infrared (FT-IR) spectroscopy at different temperatures. The olefinic (CH) band at 3012 cm-1 was used to probe diabetes-induced lipid peroxidation. The intensity and area values of this band of diabetic samples were found to be increased significantly (P<0.05) compared with nondiabetic samples. The increase in olefinic band intensity is attributed mainly to the lipid peroxidation end products. The results of the FT-IR study were found to be in agreement with biochemical studies that revealed a significant increase in malondialdehyde levels of diabetic samples compared with control samples (P<0.05) using the thiobarbituric acid test.     

Genetic diversity analysis of North Africa’s barley using SSR markers

It was demonstrated that some North Africa barley accessions have diverse tolerance sources for abiotic stresses and a good nutritional quality, but the studies done were incomplete since they were realized separately in each country apart.To implement a more complete analysis, 31 barley accessions originated from North Africa (Algeria, Tunisia and Egypt) were analyzed using 11 SSR markers selected from the seven barley linkage groups for studying the genetic diversity among these chosen barley accessions.Over the 11 SSR markers, a total of 478 reproducible bands were scored with an average of 2.13 alleles/primer and the average polymorphism information content of 0.5.Genetic distance analysis of the 31 accessions showed a large genetic diversity and high number of different groups. The most accessions are clustered according to their eco-geographical origin, according to their pedigree and agronomic characters or according to the caryopsis character (hulled or naked caryopsis). This high number of obtained groups is an invaluable aid in crop improvement strategies and confirms the opinion suggesting that North Africa could be a secondary center of origin of barley. The various growing conditions and the multiple uses of barley in each country may be the cause of the large variability of the barley germplasm in each region.     

Oxidative stress in plant cell culture: a role in production of beta-thujaplicin by Cupresssus lusitanica suspension culture

Oxidative stress is a common physiological stress that often challenges plants. Reactive oxygen species (ROS) are major factors in oxidative stress that significantly affect plant cell growth and secondary metabolism. Here we used beta-thujaplicin production by Cupressus lusitanica cell culture as an example to demonstrate the common occurrence of oxidative stress in cultivated plant cells and its effect on multiple aspects of cell culture process. C. lusitanica cells cultivated under Fe(2+) stress generate a significant level of ROS, and oxidative stress also occurs at late stages of C. lusitanica cell cultures under normal conditions. ROS production inhibited cell growth, induced lipid peroxidation and cell death, and enhanced ethylene and beta-thujaplicin production. It is demonstrated that Fe(2+) stress enhances ROS production via the Fenton reaction and promotes beta-thujaplicin production via ROS-induced lipid peroxidation that may activate cyclic oxylipin and ethylene pathways. Results further indicate that H(2)O(2) is a positive signal for beta-thujaplicin production, whereas superoxide anion radical (O(2) (- )) negatively affects beta-thujaplicin induction and strongly induces cell death. The study suggests that evaluating the oxidative stress and plant responses in a cell culture process is very necessary and important for understanding biochemical processes and for gaining the maximal productivity of target secondary metabolites.     

Drought acclimation reduces O2*- accumulation and lipid peroxidation in wheat seedlings

Abiotic stresses cause ROS accumulation, which is detrimental to plant growth. It is well known that acclimation of plants under mild or sub-lethal stress condition leads to development of resistance in plants to severe or lethal stress condition. The generation of ROS and subsequent oxidative damage during drought stress is well documented in the crop plants. However, the effect of drought acclimation treatment on ROS accumulation and lipid peroxidation has not been examined so far. In this study, the effect of water stress acclimation treatment on superoxide radical (O(2)(-z.rad;)) accumulation and membrane lipid peroxidation was studied in leaves and roots of wheat (Triticum aestivum) cv. C306. EPR quantification of superoxide radicals revealed that drought acclimation treatment led to 2-fold increase in superoxide radical accumulation in leaf and roots with no apparent membrane damage. However under subsequent severe water stress condition, the leaf and roots of non-acclimated plants accumulated significantly higher amount of superoxide radicals and showed higher membrane damage than that of acclimated plants. Thus, acclimation-induced restriction of superoxide radical accumulation is one of the cellular processes that confers enhanced water stress tolerance to the acclimated wheat seedlings.     

Targeting sources of drought tolerance within an Avena spp. collection through multivariate approaches

In this study, we find and characterize the sources of tolerance to drought amongst an oat (Avena sativa L.) germplasm collection of 174 landraces and cultivars. We used multivariate analysis, non-supervised principal component analyses (PCA) and supervised discriminant function analyses (DFA) to suggest the key mechanism/s responsible for coping with drought stress. Following initial assessment of drought symptoms and area under the drought progress curve, a subset of 14 accessions were selected for further analysis. The collection was assessed for relative water content (RWC), cell membrane stability, stomatal conductance (g ₁), leaf temperature, water use efficiency (WUE), lipid peroxidation, lipoxygenase activity, chlorophyll levels and antioxidant capacity during a drought time course experiment. Without the use of multivariate approaches, it proved difficult to unequivocally link drought tolerance to specific physiological processes in the different resistant oat accessions. These approaches allowed the ranking of many supposed drought tolerance traits in the order of degree of importance within this crop, thereby highlighting those with a causal relationship to drought stress tolerance. Analyses of the loading vectors used to derive the PCA and DFA models indicated that two traits involved in water relations, temperature and RWC together with the area of drought curves, were important indicators of drought tolerance. However, other parameters involved in water use such as g ₁ and WUE were less able to discriminate between the accessions. These observations validate our approach which should be seen as representing a cost-effective initial screen that could be subsequently employed to target drought tolerance in segregating populations.     

Changes in the biochemical status of plant cells induced by the environmental pollutant ozone

Tropospheric ozone will increase during the next decades and will reach the critical threshold concentration of 40 nl l⁻¹ more often in rural regions than in urban areas. Damage inflicted on plants by ozone can be divided into chronic and acute damage, reflecting different defence strategies of the plants. Chronic damage, somewhat similar to a premature senescence, follows disturbances in sugar metabolism, inhibition of photosynthesis, disbalances in the redox-status and ROS-production in the chloroplast stroma. The acute damage resembles the hypersensitive response which occurs after a pathogen attack. Either the accumulation of reactive oxygen species (ROS) or the efficiency of scavenging systems in the apoplast may govern the spread of cell death. Probably, different signalling pathways mediate the plant responses, such as ethylene, salicylate and ROS. ROS production and lipid peroxidation take place either on the plasma membrane or in the chloroplastic membrane and lipid hydroperoxides and derivatives, such as jasmonate, can act as signals for subsequent plant reactions. Both kinds of plant responses, i.e., acute as well as chronic damage, can affect the plants' abilities to respond to further stress attacks.     

玉米种质资源对六种重要病虫害的抗性鉴定与评价

在2003-2005年间,对604份玉米种质进行了抗弯孢菌叶斑病和玉米螟鉴定,筛选出抗弯孢菌叶斑病的材料93份,抗玉米螟材料22份。2006-2009年间,对836份玉米种质进行了抗大斑病、茎腐病、穗腐病和瘤黑粉病的鉴定与评价,筛选出一批高抗和多抗的资源。在836份资源中,对大斑病1、2和N号3个生理小种具有抗性的材料均为50%左右;抗茎腐病材料为41.3%,高抗和抗性种质分别为264和81份;穗腐病高抗和抗性种质分别为5和171份,占比为21.1%;瘤黑粉病高抗和抗性种质各261和14份,占总鉴定材料的32.9%。上述结果表明抗大斑病、茎腐病和瘤黑粉病的种质资源较为丰富。通过对抗性结果进行对比分析,发现不同生态区玉米种质的抗性强弱以及抗性多样性存在明显差异,黑龙江和内蒙古的种质对病虫害的抗性强弱及多样性程度明显高于四川种质。此外,玉米自交系对病虫害的抗性强弱以及多抗性程度高于农家种。     

Melatonin reduces Fenton reaction-induced lipid peroxidation in porcine thyroid tissue

Free radicals and reactive oxygen species (ROS) participate in physiological and pathological processes in the thyroid gland. Bivalent iron cation (ferrous, Fe(2+)), which initiates the Fenton reaction (Fe(2+) + H2O2 --> Fe(3+) + *OH + OH(-)) is frequently used to experimentally induce oxidative damage, including that caused by lipid peroxidation. Lipid peroxidation is involved in DNA damage, thus indirectly participating in the early steps of carcinogenesis. In turn, melatonin is a well-known antioxidant and free radical scavenger. The aim of the study was to estimate the effect of melatonin on basal and iron-induced lipid peroxidation in homogenates of the porcine thyroid gland. In order to determine the effect of melatonin on the auto-oxidation of lipids, thyroid homogenates were incubated in the presence of that indoleamine in concentrations of 0.0, 0.00001, 0.0001, 0.001, 0.01, 0.1, 0.25, 0.5, 1.0, 2.5, or 5.0 mM. To study melatonin effects on iron-induced lipid peroxidation, the homogenates were incubated in the presence of FeSO(4) (40 microM) plus H2O2 (0.5 mM), and, additionally, in the presence of melatonin in the same concentrations as above. The degree of lipid peroxidation was expressed as the concentration of malondialdehyde + 4-hydroxyalkenals (MDA + 4-HDA) per mg protein. Melatonin, in a concentration-dependent manner, decreased lipid peroxidation induced by Fenton reaction, without affecting the basal MDA + 4-HDA levels. In conclusion, melatonin protects against iron + H2O2-induced peroxidation of lipids in the porcine thyroid. Thus, the indoleamine would be expected to prevent pathological processes related to oxidative damage in the thyroid, cancer initiation included.     

水杨酸调节决明根系铝诱导的氧化胁迫

水杨酸(Salicylicacid,SA)在调节生物和非生物胁迫,诱导植物氧化胁迫中起着重要的作用,但对铝诱导的氧化胁迫的调节作用尚不清楚。本文研究了SA对决明(CassiatoraL.)根系铝诱导的H2O2和O2-含量变化,包括抗氧化酶活性以及细胞质膜过氧化胁迫变化的影响。介质中20mmol/L铝处理增加质膜透性,导致MDA含量上升及根尖细胞Evansblue染色加重(测定细胞死亡),而外源供给5mmol/LSA能缓解铝诱导的氧化胁迫。SA处理能明显降低根尖H2O2和O2-的含量,但两者含量与CAT、APX和GR的活性变化没有相关性,而与POD活性增加有关。水杨酸诱导H2O2含量的下降与抑制O2-积累和SOD活性有关。结果表明,SA可能激活一条由H2O2介导的、依赖于POD的抗氧化机制来缓解脂质的过氧化作用。     

Haplotype diversity and population structure in cultivated and wild barley evaluated for Fusarium head blight responses

Fusarium head blight (FHB) is a threat to barley (Hordeum vulgare L.) production in many parts of the world. A number of barley accessions with partial resistance have been reported and used in mapping experiments to identify quantitative trait loci (QTL) associated with FHB resistance. Here, we present a set of barley germplasm that exhibits FHB resistance identified through screening a global collection of 23,255 wild (Hordeum vulgare ssp. spontaneum) and cultivated (Hordeum vulgare ssp. vulgare) accessions. Seventy-eight accessions were classified as resistant or moderately resistant. The collection of FHB resistant accessions consists of 5, 27, 46 of winter, wild and spring barley, respectively. The population structure and genetic relationships of the germplasm were investigated with 1,727 Diversity Array Technology (DArT) markers. Multiple clustering analyses suggest the presence of four subpopulations. Within cultivated barley, substructure is largely centered on spike morphology and growth habit. Analysis of molecular variance indicated highly significant genetic variance among clusters and within clusters, suggesting that the FHB resistant sources have broad genetic diversity. The haplotype diversity was characterized with DArT markers associated with the four FHB QTLs on chromosome 2H bin8, 10 and 13 and 6H bin7. In general, the wild barley accessions had distinct haplotypes from those of cultivated barley. The haplotype of the resistant source Chevron was the most prevalent in all four QTL regions, followed by those of the resistant sources Fredrickson and CIho4196. These resistant QTL haplotypes were rare in the susceptible cultivars and accessions grown in the upper Midwest USA. Some two- and six-rowed accessions were identified with high FHB resistance, but contained distinct haplotypes at FHB QTLs from known resistance sources. These germplasm warrant further genetic studies and possible incorporation into barley breeding programs.     

Mitochondria: omega-3 in the route of mitochondrial reactive oxygen species

Mitochondria are the main organelles that produce reactive oxygen species (ROS). Overproduction of ROS induces oxidative damage to macromolecules, including lipids, and can damage cellular membrane structure and functions. Mitochondria, the main target of ROS-induced damage, are equipped with a network of antioxidants that control ROS production. Dietary intake of omega-3 polyunsaturated fatty acids (ω3PUFAs) and consequently the increase in ω3PUFA content of membrane lipids may be disadvantageous to the health because ROS-induced oxidative peroxidation of ω3PUFAs within membrane phospholipids can lead to the formation of toxic products. Mitochondrial control of lipid peroxidation is one of the mechanisms that protect cell against oxidative damage. This review discusses the role of mitochondria in ROS generation and the mechanisms by which it regulates ROS production. The susceptibility to peroxidation of PUFAs by ROS raises the question of the adverse effects of ω3PUFA dietary supplementation on embryonic development and prenatal developmental outcomes.     

The upstream oxylipin profile of Arabidopsis thaliana: a tool to scan for oxidative stresses

Various physiological imbalances lead to reactive oxygen species (ROS) overproduction and/or increases in lipoxygenase (LOX) activities, both events ending in lipid peroxidation of polyunsaturated fatty acids (PUFAs). Besides the quantification of such a process, the development of tools is necessary in order to allow the identification of the primary cause of its development and localization. A biochemical method assessing 9 LOX, 13 LOX and ROS-mediated peroxidation of membrane-bound and free PUFAs has been improved. The assay is based on the analysis of hydroxy fatty acids derived from PUFA hydroperoxides by both the straight and chiral phase high-performance liquid chromatography. Besides the upstream products of peroxidation of the 18:2 and 18:3 PUFAs, products coming from the 16:3 were characterized and their steady-state level quantified. Moreover, the observation that the relative amounts of the ROS-mediated peroxidation isomers of 18:3 were constant in leaves allowed us to circumvent the chiral analyses for the discrimination and quantification of 9 LOX, 13 LOX and ROS-mediated processes in routine experiments. The methodology has been successfully applied to decipher lipid peroxidation in Arabidopsis leaves submitted to biotic and abiotic stresses. We provide evidence of the relative timing of enzymatic and non-enzymatic lipid peroxidation processes. The 13 LOX pathway is activated early whatever the nature of the stress, leading to the peroxidation of chloroplast lipids. Under cadmium stress, the 9 LOX pathway added to the 13 LOX one. ROS-mediated peroxidation was mainly driven by light and always appeared as a late process.     

臭氧胁迫对大豆叶片抗坏血酸-谷胱甘肽循环的影响

由于城市化的加剧导致近地面臭氧（O3）浓度日益增加,对植物生长和生态系统的功能产生了显著影响,因此准确评估近地层O3浓度升高对植物的影响具有重要意义。本文利用开顶式气室（OTCs）,系统探讨了模拟O3胁迫下大豆抗氧化系统抗坏血酸（AsA）-谷胱甘肽（GSH）循环清除活性氧（ROS）的机制及其对植株生长发育的影响。结果表明,在整个生育期内,与对照相比, 80?10 nL?L-1和110?10 nL?L-1 O3可以使大豆叶片丙二醛（MDA）含量、相对电导率增大,超氧阴离子（O2 ）产生速率、过氧化氢（H2O2）含量升高,超氧化物歧化酶（SOD）活性减弱; AsA-GSH循环中的AsA、GSH含量减少,脱氢抗坏血酸（DHA）、氧化型谷胱甘肽（GSSG）含量增加,过氧化物酶（APX）、单脱氢抗坏血酸还原酶（MDHAR）、谷胱甘肽还原酶（GR）活性呈现出前期增强后期减弱趋势,而脱氢抗坏血酸还原酶（DHAR）活性呈现出增强-减弱-增强的趋势。以上结果说明,O3浓度升高促进了大豆叶片ROS的代谢速率,降低了AsA-GSH循环效率,表明抗氧化系统不能长时间忍受高浓度O3带来的氧化伤害,从而使膜脂过氧化程度加重,对大豆表现为伤害效应。