Comparison of Hexaploid and Tetraploid Wheat Cultivars in their Responses to Water Stress

We studied the effect of water stress imposed at anthesis and pre-anthesis stages on oxidative stress and antioxidant activity in four wheat cultivars, two hexaploid Triticum aestivum cultivars, drought resistant cv. C 306 and drought susceptible cv. Hira, and two tetraploid cultivars, T. durum cv. A 9-30-1 and T. dicoccum cv. HW 24. Water stress decreased relative water content (RWC), membrane stability index (MSI), and increased H₂O₂ and malondialdehyde (MDA) contents as well as activity of superoxide dismutase (SOD), catalase (Cat) and peroxidase (POX) in all the genotypes at all the stages. Both the tetraploid cultivars showed higher RWC, MSI and SOD activity, and lower H₂O₂ and MDA contents under water stress than hexaploid ones. Cat and POX activities were highest in C 306.     

Responses of Wheat Seedlings to Exogenous Selenium Supply Under Cold Stress

Dose-dependent effects of selenium on growth and physiological trait of wheat seedlings (Triticum aestivum L. cv Han NO.7086) exposed to cold stress are reported. Responses of seedlings were different depending on the Se concentration. The treatments with 0.5 and 1.0 mg Se kg⁻¹ significantly increased biomass and chlorophyll content of seedlings. However, the treatments at 2.0 and 3.0 mg Se kg⁻¹ only induced an evident increase in chlorophyll content and did not promote biomass accumulation of seedlings. Antioxidant compounds content (anthocyanins, flavonoids, and phenolic compounds) and antioxidant enzymes’ activities (peroxidase and catalase) increased by different Se treatments, while only the treatment with 1.0 mg Se kg⁻¹ induced a significant reduce in malondialdehyde content and the rate of superoxide radical production of wheat seedlings. The results of this study demonstrated that Se supply could increase antioxidant capacity of seedlings, and optimal Se supply reduced production of free radicals, membrane lipid peroxidation, and promoted biomass accumulation.     

Molecular Analysis of Leaf Rust-Resistant Introgression Lines Obtained by Crossing of Hexaploid Wheat Triticum aestivum with Tetraploid Wheat Triticum timopheevii

Twenty-four Triticum aestivum×T. timopheevii hybrid lines developed on the basis of five varieties of common wheat and resistant to leaf rust were analyzed by the use of microsatellite markers specific for hexaploid wheat T. aestivum. Investigation of intervarietal polymorphism of the markers showed that the number of alleles per locus ranged from 1 to 4, depending on the marker (2.5 on average). InT. timopheevii, amplification fragments are produced by 80, 55, and 30% of primers specific to the A, B, and D common wheat genomes, respectively. Microsatellite analysis revealed two major areas of introgression of the T. timopheevii genome: chromosomes of homoeological groups 2 and 5. Translocations were detected in the 2A and 2B chromosomes simultaneously in 11 lines of 24. The length of the translocated fragment in the 2B chromosome was virtually identical in all hybrid lines and did not depend on the parental wheat variety. In 15 lines developed on the basis of the Saratovskaya-29, Irtyshanka, and Tselinnaya-20, changes occurred in the telomeric region of the long arm of the 5A chromosome. Analysis with markers specific to the D genome suggested that introgressions of the T. timopheevii genome occurred in chromosomes of the D genome. However, the location of these markers on T. timopheevii chromosomes is unknown. Our data suggest that the genes for leaf rust resistance transferred from T. timopheevii to T. aestivum are located on chromosomes of homoeological group 2.     

Antioxidant Responses of Lentil to Cold and Drought Stress

The effects of cold and drought stress on antioxidant responses and growth parameters in shoots and roots of lentil (Lens culinaris M cv Sultan 1) seedlings were investigated. Ten-day-old hydroponically grown seedlings were subjected to drought and cold (4°C) stress for 5 days. The length and fresh weight of shoots decreased significantly under both stress conditions, contrary to the increase in these growth parameters for roots under the same conditions. The oxidative damage as generation of malondialdehyde and hydrogen peroxide, was markedly higher in shoots under cold. Both stress conditions caused a significant increase in malondialdehyde levels in root tissues. The increase in proline levels was more pronounced under cold stress in shoots and roots. The tested stress conditions had no significant effect on chlorophyll contents. Superoxide dismutase activity was differentially altered in shoot and root tissues under drought and cold stress. The catalase activity was higher in roots under drought stress. On the other hand, ascorbate peroxidase activity increased in root tissues under cold stress. The results indicate that improved tolerance to cold and drought stress in root and shoot tissues of lentil might be correlated to the increased capacity of antioxidative defense system.     

Effects of Soil Flooding on Growth and Grain Yield of Populations of Tetraploid and Hexaploid Species of Wheat

Single populations of three hexaploid species of wheat, Triticumaestivum, Triticum spelta and Triticum macha, and two populationsof the tetraploid wheat, Triticum dicoccum (Pontus and Bordeaux),were grown in a greenhouse experiment at a range of soil floodingregimes: free draining, two levels of transient flooding andcontinuous flooding. Increasing severity of flooding treatment resulted in increasedsoil reduction and an increase in the concentration of reducediron and manganese in the experimental soil, and also resultedin a reduction in vegetative growth, number of inflorescences,grain number and grain weight. There were, however, large differencesbetween the wheat populations in the degree of reduction inyield caused by flooding. The population of T. macha was muchmore flooding-tolerant than the other hexaploid species andthe ‘Pontus’ population of the emmer wheat, T. dicoccum,was more tolerant than the ‘Bordeaux’ populationof this species and than T. spelta and T. aestivum. The results are discussed in relation to the origin of the populations. Soil flooding, Triticum aeslivum, Triticum macha, Triticum spelta, Triticum dicoccum     

Expression of Vernalization Requirement and Spikelet Number in Synthetic Hexaploid Wheats and their Triticum tauschii and Tetraploid Wheat Parents

Vernalization requirement, as measured by days from sowing toear emergence (plants grown under an 18-h photoperiod), andspikelet number per ear were recorded for 17 synthetic hexaploidwheats and the six tetraploid (Triticum durum) and the ninediploid T. tauschii parents used to synthesize them. The tetraploid parents and the synthetic hexaploids had springphenotypes (little or no vernalization requirement) whereasthe T. tauschii parents were all winter types (strong vernalizationrequirement). The tetraploid wheats and the synthetic hexaploidsreached ear emergence 50·3 to 63·8 d and 58·2to 75·3 d after sowing, respectively, while the T. tauschiilines reached ear emergence 114·3 to 179·5 d aftersowing. The spring habit of the synthetic hexaploids demonstrates theepistasis of spring over winter habit. It is considered thatwith a presumed single vrn locus in the diploid species T. tauschiithe range of ear emergence in these lines is consistent withthe action of multiple alleles at that locus. Although there was no general epistasis for spikelet number,the tetraploid parents appear to be exerting more influenceover spikelet number in the synthetic hexaploids than T. tauschii.The well established association between the duration from sowingto ear emergence and spikelet number was not evident eitherwithin each ploidy group or when the 32 lines were consideredtogether. Triticum tauschii, Triticum durum, hexaploid wheat, spikelet number, vernalization requirement     

基于cDNA-AFLP及MSAP技术分析西瓜同源二倍体和四倍体低温胁迫差异表达

为了研究西瓜二倍体及同源四倍体在低温胁迫下的分子机制,以西瓜‘京欣’1号母本83166（二倍体）及其同源四倍体为材料,利用MSAP及cDNA-AFLP技术研究低温处理前后基因表达的差异,并对差异带进行克隆、测序和比对。22对MSAP引物扩增得到1564个位点,其中二倍体经低温处理后总甲基化率下降2.8%,四倍体下降6.4%。将12条差异带与西瓜基因组数据库比对,有7条带确定是西瓜基因组序列。26对cDNA-AFLP引物组合扩增出1267条带,其中二倍体上调表达占48.2%,下调表达占51.8%;四倍体上调表达占58.6%,下调表达占41.4%。23条差异带在NCBI中找到了同源序列基因,包括假定蛋白（39.13%）、能量与代谢（43.48%）、物质运输（8.70%）、转录相关（4.35%）以及逆境相关（4.35%）,另有10条无同源序列。低温胁迫后,四倍体去甲基化率与上调表达量均高于二倍体,而且四倍体诱导出的差异基因参与了物质的能量代谢调控及逆境胁迫过程,说明四倍体较二倍体有更强的耐冷性。     

HRGP在小麦抗寒锻炼过程中的变化及其与抗寒性的关系

强抗寒小麦品种(R-025、中品94-19、品83-1、品83-2、品83-3、米罗诺夫808)经抗寒锻炼后,其幼苗体内的游离脯氨酸、细胞壁结合的羟脯氨酸和糖蛋白含量发生了明显的变化.游离脯氨酸含量比未经抗寒锻炼处理时增加5～32倍,细胞壁结合的羟脯氨酸含量比对照增加1.77～2.17倍,糖蛋白含量比对照增加4.68～9.72倍,而不抗寒小麦品种(中国春、冬103)增加量较小.脯氨酸积累进程各个品种间差异比较大,品83-1、品83-2积累较快,抗寒锻炼第21d时达到最高峰,而R-025在第56d达到最高峰.脯氨酸含量与小麦品种抗寒性相关不显著(相关系数为0.3462),而羟脯氨酸含量、糖蛋白含量与小麦品种抗寒性相关显著,相关系数分别为0.6491和0.7039.从小麦细胞壁纯化得到了2种伸展蛋白Extensm1和Ex-tensin2,其含量都和小麦品种抗寒性呈正相关.Extensin1是分子量为28kD、羟脯氨酸为主要成份(32mo1%)的富含羟脯氨酸糖蛋白.     

哺乳动物冷应激的主要神经内分泌反应

为便于了解哺乳动物冷应激生理变化的调节机理,介绍了冷应激的主要神经内分泌反应。控制冷应激反应的主要中枢位于下丘脑。冷应激激活交感神经系统,激活下丘脑－垂体－甲状腺轴和下丘脑－垂体－肾上腺轴激素的合成和分泌,引起肾上腺髓质儿茶酚胺分泌增加;同时抑制促生长激素轴、促性腺轴、催乳激素轴的激素分泌。神经肽Y、瘦素、褪黑激素等多种神经肽和激素参与冷应激反应。     

小麦根系特征对干旱胁迫的响应

干旱胁迫时, 小麦(Triticum aestivum)根系率先产生应激响应, 同时向地上部发出信号, 诱导地上部发生生理反应, 从而提高植株抗旱能力。根系构型包括平面几何性状和立体几何结构(即拓扑构型), 具有遗传稳定性和可塑性。干旱胁迫影响根系理化特性, 如根源化学信号、根系细胞酶类和根系渗透作用的响应。根系通过调整其解剖学结构和水分吸收动力等来适应干旱胁迫。该文从根系构型、理化特性和解剖学结构3个方面, 系统阐述了小麦根系特征对干旱胁迫的响应, 并探讨了其与干旱胁迫的关系和当前研究中存在的问题, 以期为相关研究提供参考。     

Water and Nutrient Use Efficiency in Diploid, Tetraploid and Hexaploid Wheats

Three diploid (Triticum boeoticum, AA; Aegilops speltoides, BB and Ae. tauschii, DD), two tetraplold (T. dlcoccoides,AABB and T. dicoccon, AABB) and one hexaploid (T. vulgare, AABBDD) varieties of wheat, which are very important in the evolution of wheat were chosen in this study. A pot experiment was carried out on the wheat under different water and nutrient conditions (i) to understand the differences in biomass, yield, water use efficiency (WUE), and nutrient (N, P and K) use efficiency (uptake and utilization efficiency) among ploldles in the evolution of wheat; (ii) to clarify the effect of water and nutrient conditions on water and nutrient use efficiency; and (iii) to assess the relationship of water and nutrient use efficiency in the evolution of wheat. Our results showed that from diploid to tetraploid then to hexaploid during the evolution of wheat, both root biomass and above-ground biomass increased initially and then decreased. Water consumption for transpiration decreased remarkably, correlating with the decline of the growth period, while grain yield, harvest index, WUE, N, P and K uptake efficiency, and N, P and K utilization efficiency increased significantly. Grain yield, harvest index and WUE decreased in the same order: T.vulgare ＞ T. dicoccon ＞ T. dicoccoides ＞ Ae. tauschii ＞ Ae. speltoides ＞ T. boeoticum. Water stress significantly decreased root biomass, above-ground biomass, yield, and water consumption for transpiration by 47-52%, butremarkably increased WUE. Increasing the nutrient supply increased wheat above-ground biomass, grain yield,harvest index, water consumption for transpiration and WUE under different water levels, but reduced root biomass under drought conditions. Generally, water stress and low nutrient supply resulted in the lower nutrientuptake efficiency of wheat. However, water and nutrient application had no significant effects on nutrient utilization efficiency, suggesting that wheat nutrient utilization efficiency is mainly controlled by genotypes. Compared to theother two diploid wheats, Ae. squarrosa (DD) had significant higher WUE and nutrient utilization efficiency, Indicating that the D genome may carry genes controlling high efficient utilization of water and nutrient. Significant relationships were found between WUE and N, P and K utilization efficiency.     

小麦根系特征对干旱胁迫的响应

干旱胁迫时, 小麦(Triticum aestivum)根系率先产生应激响应, 同时向地上部发出信号, 诱导地上部发生生理反应, 从而提高植株抗旱能力。根系构型包括平面几何性状和立体几何结构(即拓扑构型), 具有遗传稳定性和可塑性。干旱胁迫影响根系理化特性, 如根源化学信号、根系细胞酶类和根系渗透作用的响应。根系通过调整其解剖学结构和水分吸收动力等来适应干旱胁迫。该文从根系构型、理化特性和解剖学结构3个方面, 系统阐述了小麦根系特征对干旱胁迫的响应, 并探讨了其与干旱胁迫的关系和当前研究中存在的问题, 以期为相关研究提供参考。     

Ribulose-1,5-bisphosphate Carboxylase/Oxygenase Content and Degradation in Diploid,Tetraploid, and Hexaploid Wheat Species during Monocarpic Senescence

Wheat provides a unique genetic system in which variable sink size is available across the ploidies. We characterized monocarpic senescence in diploid, tetraploid, and hexaploid wheat species in flag leaf from anthesis up to full grain maturity at regular intervals. Triticum tauschii Acc. cv. EC-331751 showed the fastest rate of senescence among the species studied and the rate of loss per day was highest in terms of photosynthesis rate, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) content, and flag leaf N content coupled with a higher rate of gain in grain N content. Cultivars Kundan and HD 4530 maintained high flag leaf N content throughout grain filling as compared to the diploids and showed a slower rate of senescence. RuBPCO content was higher in the diploids as compared to Kundan and HD 4530 at anthesis. However, the rate of decline in RuBPCO content per day was also higher in the diploids. This degradation in RuBPCO was mediated by high endoproteolytic activities in the diploids which in turn supported its higher rate of N mobilization as compared to the tetraploid and hexaploid wheat. Acidic endopeptidases were responsible for the mobilization of flag leaf nitrogen in wheat across ploidy levels (r=–0.582, p<0.01).     

6个棉花品种幼苗对低温胁迫的响应

4 ℃低温条件处理6个不同熟性棉花品种幼苗,测定供试材料叶片中SOD活性、POD活性、超氧阴离子含量、可溶性糖含量、可溶性蛋白含量、MDA、相对电导率以及根系活体染色等8项指标,比较不同棉花品种苗期抗冷性差异.对测定指标进行综合评价结果显示：4 ℃低温胁迫1 d后,6个品种耐冷性由强到弱依次为中50＞N203＞N52＞K-1＞N181＞N177;4 ℃低温胁迫2 d后,耐冷性顺序为中50＞N177＞N52＞K-1＞N203＞N181;4 ℃低温胁迫3d后N52＞中50＞N203＞K-1＞N177＞N181.各生理指标综合评判结果为早熟品种中50和N52耐受性较强.     

Differences in Zinc Efficiency among and within Diploid, Tetraploid and Hexaploid Wheats

Greenhouse experiments were carried out with six diploid, ninetetraploid and seven hexaploid wheats, including wild and primitivegenotypes, to study the influence of varied zinc (Zn) supplyon the severity of Zn deficiency symptoms, shoot dry matterproduction and shoot Zn concentrations. In addition to wildand primitive genotypes, one modern tetraploid cultivar withhigh sensitivity to Zn deficiency and two modern hexaploid cultivars,one highly sensitive to and one resistant to Zn deficiency,were included for comparison. Plants were grown for 44 d ina severely Zn-deficient calcareous soil, with (+Zn; 5 mg Znkg^-1soil) and without (-Zn) Zn fertilization. Visible Zn deficiencysymptoms, including whitish-brown necrotic patches on leaf blades,appeared very rapidly and severely in all tetraploid wheat genotypes.Compared with tetraploid wheats, diploid and hexaploid wheatswere less sensitive to Zn deficiency. With additional Zn, shootdry matter production was higher in tetraploid than diploidand hexaploid wheats. However, under Zn-deficient conditionstetraploid wheats had the lowest shoot dry matter production,indicating the very high sensitivity of tetraploid wheats toZn deficiency. Consequently, Zn efficiency expressed as theratio of shoot dry matter produced under Zn deficiency to Znfertilization, was much lower in tetraploid wheats than in diploidand hexaploid wheats. On average, Zn efficiency ratios were36% for tetraploid, 60% for diploid and 64% for hexaploid wheats.Differences in Zn efficiency among and within diploid, tetraploidand hexaploid wheats were positively related to the amount ofZn per shoot of the genotypes, but not to the amount of Zn perunit dry weight of shoots or seeds used in the experiments.The seeds of the accessions of tetraploid wild wheats containedup to 120 mg Zn kg^-1, but the resulting plants showed very highsensitivity to Zn deficiency. By contrast, hexaploid wheatsand primitive diploid wheats with much lower Zn concentrationsin seeds had higher Zn efficiencies. It is suggested that notonly enhanced Zn uptake capacity but also enhanced internalZn utilization capacity of genotypes play important roles indifferential expression of Zn efficiency. The results of thisstudy also suggest the importance of the A and D genomes asthe possible source of genes determining Zn efficiency in wheat.Copyright 1999 Annals of Botany Company Seeds, Triticum aestivum, Triticum monococcum, Triticum turgidum, zinc concentrations, zinc deficiency, zinc efficiency.     

Comparative Analysis and Identification of miRNAs and Their Target Genes Responsive to Salt Stress in Diploid and Tetraploid Paulownia fortunei Seedlings

Salt stress is a global environmental problem that affects plant growth and development. Paulownia fortunei is an adaptable and fast-growing deciduous tree native to China that is environmentally and economically important. MicroRNAs (miRNAs) play important regulatory roles in growth, development, and stress responses in plants. MiRNAs that respond to biotic stresses have been identified; however, how miRNAs in P. fortunei respond to salt stress has not yet been reported. To identify salt-stress-responsive miRNAs and predict their target genes, four small RNA and four degradome libraries were constructed from NaCl-treated and NaCl-free leaves of P. fortunei seedlings. The results indicated that salt stress had different physiological effects on diploid and tetraploid P. fortunei. We detected 53 conserved miRNAs belonging to 17 miRNA families and 134 novel miRNAs in P. fortunei. Comparing their expression levels in diploid and tetraploid P. fortunei, we found 10 conserved and 10 novel miRNAs that were significantly differentially expressed under salt treatment, among them eight were identified as miRNAs probably associated with higher salt tolerance in tetraploid P. fortunei than in diploid P. fortunei. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses were performed to predict the functions of the target genes of the conserved and novel miRNAs. The expressions of 10 differentially expressed miRNAs were validated by quantitative real-time polymerase chain reaction (qRT-PCR). This is the first report on P. fortunei miRNAs and their target genes under salt stress. The results provided information at the physiological and molecular levels for further research into the response mechanisms of P. fortunei to salt stress.     

小麦胚芽鞘扩展蛋白特性及对水分胁迫的响应

扩展蛋白是植物细胞壁延伸过程中的关键调节因子,在植物的生长发育以及对逆境的响应过程中起着重要作用。本文选用小麦(HF 9703)胚芽鞘为材料,采用Hepes法和SDS法分别提取小麦胚芽鞘扩展蛋白,通过改良的植物组织伸长测定仪测定其活性,并利用扩展蛋白抗体进行免疫印迹以检测其丰度,主要研究了小麦胚芽鞘扩展蛋白的特性及对水分胁迫的响应。结果表明:Hepes法提取的扩展蛋白活性较高,而SDS法的提取效率高;离体小麦胚芽鞘扩展蛋白的活性具有pH依赖性,且随缓冲液的交替更换(pH 4.5:pH 6.8)而反复逆转;扩展蛋白主要定位于细胞壁中;小麦胚芽鞘扩展蛋白和黄瓜下胚轴扩展蛋白具有交叉重组活性,但这种活性具有种属特异性。水分胁迫诱导小麦胚芽鞘扩展蛋白的活性和丰度提高,扩展蛋白活性的提高在小麦对水分胁迫的抗性方面可能具有重要作用。     

小麦耐盐细胞系对盐胁迫的伤害性反应

通过逐级提高ＮａＣｌ浓度的筛选方法,得到了能在１．５％ＮａＣｌ下生长良好的小麦（ＴｒｉｔｉｃｕｍａｅｓｔｉｖｕｍＬ．）耐盐细胞系。在盐分胁迫下,耐盐细胞系含水量的降低幅度小于不耐盐细胞系（对照）,Ｈ２Ｏ２含量和Ｏ－２产生速率的增加幅度也明显小于对照细胞系。同时,膜的相对透性、膜脂过氧化和脱酯化程度的提高幅度也明显低于对照细胞系。表明盐分对小麦细胞系膜的伤害与活性氧介导的膜脂过氧化和脱酯化有关,而耐盐细胞系比对照细胞系表现出较强的抗活性氧伤害的能力。