镉胁迫下萝卜基因组DNA甲基化敏感扩增多态性分析

应用甲基化敏感扩增多态性(MSAP)技术分析了重金属镉(cd)胁迫处理后萝卜基因组DNA甲基化程度的变化。结果表明,经50、250和500mg/L CdCl_2处理后,MSAP比率分别为37%、43%和51%,均高于对照(34%);全甲基化率(双链C~mCGG)分别为23%、25%和27%,而其对照为22%,表明重金属CdCl_2胁迫后,某些位点发生了重新甲基化。萝卜叶片DNA中总甲基化水平的增加与CdCl_2处理浓度呈显著正相关。甲基化变异可分为重新甲基化、去甲基化、不定类型以及与对照相同的甲基化模式等类型,Cd胁迫处理引起的植株基因组DNA甲基化程度的提高主要是重新甲基化。     

镉胁迫对拟南芥幼苗基因组DNA多态性的影响

应用随机扩增多态性DNA(RAPD)技术,检测了镉(Cd)胁迫对拟南芥幼苗叶片DNA多态性的影响,并结合其形态和生理指标,选取Cd污染敏感的生物标记物.结果表明:0.125～3.0 mg·L-1Cd处理21 d后,拟南芥幼苗叶片的可溶性蛋白质含量随Cd浓度的增加呈倒U字型曲线变化,但其鲜重和叶绿素含量变化均不明显;12条寡核苷酸引物中,有5条引物扩增出稳定、特异的PCR产物;拟南芥幼苗叶片基因组的RAPD图谱中,对照组RAPD图谱中分辨出44条清晰的条带;Cd胁迫使拟南芥幼苗叶片基因组的RAPD图谱发生了改变,包括条带的增加、缺失和条带荧光强度的改变,且与Cd剂量相关.实验证明,Cd影响基因组模板的稳定性,即DNA多态性对Cd污染敏感,可以作为检测Cd污染及其相关生物学效应的潜在生物标记物.     

大肠杆菌不同菌株基因组DNA的多态性分析

从大肠杆菌K12菌株JM109基因组克隆了两段DNA重复序列,长度为0.9和0.6kb,分别命名为ECR-1和ECR-6。以ECR-1和ECR-6重复序列作DNA多态性分析的探针,可以鉴别大肠杆菌非常相近的菌株。表明ECR-1和ECR-6 DNA序列可用于大肠杆菌菌株的分类、流行病学和微生态学研究以及大肠杆菌各种致病菌株的临床诊断。     

镉、铜和锌胁迫下黑藻活性氧的产生及抗氧化酶活性的变化研究

研究了不同Cd、Cu、Zn处理浓度对黑藻体内活性氧()产生及对抗氧化酶(SOD、POD、CAT)活性的分子毒理学效应以探讨高等水生植物抗氧化酶对重金属胁迫的反应。结果表明,三种重金属都不同程度地加快了产生速率;Cu使SOD、POD、CAT活性下降;Cd也都减弱了SOD和POD活性,而CAT活性在0.5—5mg/L处理浓度时增加;Zn对SOD活性也为抑制作用,当浓度为0.5—5mg/L时POD和CAT活性都上升。关联度分析发现Cd、Cu和Zn胁迫下黑藻起主要保护作用的分别为SOD、POD和CAT,而SOD最易受到影响。Cd、Cu处理下的叶绿素含量也都呈下降趋势,而0.5—5mg/L的Zn浓度刺激了叶绿素合成。所有Zn处理、0.5mg/L的Cu处理和0.5—1mg/L的Cd处理的叶绿素a/b值都大于对照值。除了Cu使可溶性蛋白含量减少外,0.5—5mg/L的Zn和0.5—1mg/L的Cd都使其含量增加。综合起来,Cu的毒性最强,其次为Cd,Zn最弱。致死阈浓度分别为:Cu:0.5—1mg/L;Cd:1—2mg/L;Zn:5—6mg/L。SOD是评价重金属对沉水植物毒性效应的灵敏指标。黑藻对水环境Cu污染反应敏感。       

低温胁迫下红松幼苗活性氧的产生及保护酶的变化

在不同低温胁迫时间下,对红松（Ｐｉｎｕｓ ｋｏｒａｉｅｎｓｉｓ Ｓｉｅｂ．ｅｔ．Ｚｕｃｃ）幼苗针叶中Ｈ２Ｏ２、Ｏ＾－．２、膜脂过氧化产物丙二醛（ＭＤＡ）、组织自动化氧化速率及保护酶超氧化物歧化酶（ＳＯＤ）、过氧化物酶（ＰＯＤ）、过氧化氢酶（ＣＡＴ）和抗坏血酸过氧化物酶（ＡＳＰ）的动态变化过程进行了测定。结果表明,随着低温胁迫时间的延长,Ｏ＾－．２产生速率和Ｈ２Ｏ２含量先上升后下降;ＭＤＡ的含量呈波     

光氧化胁迫条件下叶绿体中活性氧的产生、清除及防御

活性氧(ROS)具有双重作用,高浓度引起细胞损伤,低浓度起保护作用。在光氧化胁迫条件下,光合作用高能态的反应与O2丰富供应使叶绿体成为活性氧丰富的来源。当ROS的积累超过抗氧化剂防护系统清除能力,叶绿体及细胞不可逆的光氧化损伤就会出现。而高等植物的质粒是半自主的细胞器,有它们自己的基因组学及转录、翻译机制来控制ROS生成、保护光合作用机构免受光氧化损伤。因此,本文就光氧化胁迫期间,叶绿体中ROS的乍成、功能与防护机制进行了综述。     

活性氧引起的DNA合成抑制与小麦的抗旱性

用不同浓度的 PEG60 0 0对两个抗旱性不同的小麦品种进行干旱胁迫 ,抗旱品种的DNA合成抑制程度明显低于干旱敏感品种 ,单独增加 3种主要活性氧 · O- 2 、HO· 、H2 O2 之一 ,结果亦然 ,其中以 HO· 抑制 DNA合成作用最强。加入活性氧清除剂 VC或 DMSO可部分抵消干旱胁迫或单独增加活性氧引起的 DNA合成抑制。结果表明小麦的抗旱性与干旱胁迫后 DNA合成水平具有密切联系。     

低温胁迫下玉米幼苗叶片活性氧的产生及保护酶活性的变化

在光照和黑暗条件下, 对低温胁迫玉米幼苗叶片中超氧自由基(O₂·)产生速率、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)动态变化过程的研究结果表明, 不同强度低温胁迫后, O₂·产生速率增加;保护酶SOD 、CAT 活性下降, POD 活性升高。同一低温胁迫下光照处理后的O₂·产生速率、SOD 、CAT 、POD 活性与黑暗处理相比差异达到极显著水平。     

水分胁迫引起的两种不同生态型芦苇的DNA损伤与修复

利用DNA解链荧光分析（FADU）法检测两种不同生态型芦苇（Phragmites communis T.)在PEG6000胁迫处理后的DNA损伤。结果表明：无论是20％还是30％PEG6000胁迫处理,耐旱性强的沙丘芦苇的DNA损伤都比耐旱性弱的沼泽芦苇较轻。利用不同浓度的二乙基二硫代谢氨基甲酸钠（DDC）、H2O2、FeSO4以增加芦苇的3种活性氧（O2^-、H2O2、OH）的实验也同样显示出沙丘芦苇抵抗水分胁迫引起的DNA损伤的能力较强。同时,当加入外源活性氧清除剂二甲基亚砜（DMSO）、抗坏血酸（Vc）时,水分胁迫处理的芦苇DNA损伤表现出不同程度的减轻。当PEG胁迫处理的芦苇复水后,DNA损伤随复水时间延长而逐渐减轻,但沙丘芦苇的DNA损伤修复较快而完全。实验初步证明：水分胁迫可引起植物体内DNA损伤且该损伤与活性氧有关,植物的抗旱性与DNA损伤及修复密切相关。     

土霉素胁迫下拟南芥基因组DNA甲基化的MSAP分析

以拟南芥 (Arabidopsis thaliana)为材料,研究不同土霉素浓度下拟南芥幼苗生长发育及基因组DNA的甲基化水平和变化模式。结果表明,3、5、7\,9 μmol/L土霉素胁迫对拟南芥幼苗的根长和株高有显著抑制作用;但对拟南芥幼苗的侧根数量有显著促进作用。甲基化敏感扩增多态性 (methylation-sensitive amplification polymorphism, MSAP)分析表明,经3、5、7\,9 μmol/L土霉素处理后基因组DNA甲基化比率分别为17.91%、12.50%、11.81%和14.62%,均低于对照 (18.18%)。结果表明,拟南芥经土霉素胁迫后存在基于 DNA甲基化水平和模式改变的表观遗传变异,5-甲基胞嘧啶百分含量的变化无统一趋势或规律。与对照相比,3、5、7\,9 μmol/L土霉素胁迫下拟南芥幼苗基因组DNA的甲基化和去甲基化分别为13.29%、9.22%、8.03%、12.59%和2.80%、4.26％、5.11%、4.90％。由此推测,DNA甲基化可能是植物适应土霉素胁迫机制的机制之一。     

海岸带盐沼生态系统卤代甲烷释放研究进展

卤代甲烷是破坏臭氧层的主要物质,也是重要的痕量温室气体和有机污染物.目前,其源汇格局和全球收支存在很大的不确定性.受海陆两相交互作用影响的海岸带盐沼是卤代甲烷重要的自然来源.本文综述了卤代甲烷自然源汇的研究现状、海岸带盐沼卤代甲烷的释放规律以及主要影响因素.鉴于当前研究中存在的问题,其后的研究需在以下几个方面进一步加强: 1)较长时间尺度、更大区域范围的盐沼卤代甲烷释放规律及源汇评估研究;2)利用目前已比较成熟的稳定同位素技术,更精确地定量不同盐生植物种类以及各种生物类型对盐沼卤代甲烷的贡献比率;3)关注潮水对其产生的直接或间接影响,进一步研究潮汐涨落过程、淹水时长等对盐沼卤代甲烷释放的影响;4)人类活动和气候变化对盐沼卤代甲烷释放的影响.     

桂西北喀斯特峰丛洼地土壤物理性质的时空分异及成因

运用经典统计方法,以桂西北喀斯特峰丛洼地4个植被演替阶段(草地、灌木林、次生林、原生林)土壤表层(0～15 cm)和剖面为研究对象,采用冗余分析(RDA)方法分析土壤物理性质的时空分异成因.结果表明： 灌木林和原生林表土的粘粒(＜0.002 mm)和粉粒(0.002～0.05 mm)含量分别与其他3个演替阶段有显著差异;草地与次生林之间各粒级颗粒含量差异不显著;各演替阶段土壤砂粒(0.05～2.0 mm)含量均无显著差异;草地的容重与其他3个演替阶段差异极显著.草地粘粒含量随坡位升高而增加,其他植被类型为中坡位粘粒含量最高,且同一植被类型下不同坡位之间差异不显著.原生林0～30 cm土壤各层次间的粘粒含量变化幅度(14.55%)大于草地(7.12%)、灌木林(11.24%)和次生林(13.77%),人类干扰对表层土壤颗粒组成有很大影响.土壤物理性质主要受土壤有机碳和各演替阶段植被类型的影响,其中砂粒含量受裸岩率的影响较大.     

Reactive oxygen species production and antioxidative defense system in pea root tissues treated with lead ions: the whole roots level

The lead absorbed by the roots induce oxidative stress conditions through the Reactive oxygen species (ROS) production for the pea plants cultivated hydroponically for 96 h on a Hoagland medium with the addition of 0.1 and 0.5 mM of Pb(NO₃)₂. The alterations in \textO₂ ^{- ·} {\text{O}}_{2}^{ - \cdot } and H₂O₂ concentrations were monitored spectrophotometrically which show a rapid increase in \textO₂ ^{- ·} {\text{O}}_{2}^{ - \cdot } production during the initial 2 h, and in case of H₂O₂, during the eighth hour of cultivation. The level of ROS remained higher at all the time points for the roots of the plants cultivated with Pb²⁺ and it was proportional to metal concentration. The production of \textO₂ ^{- ·} {\text{O}}_{2}^{ - \cdot } and H₂O₂ was visualized by means of fluorescence microscope technique. They are produced in nonenzymatic membrane lipid peroxidation and its final product is Malondialdehyde, the level of which increased together with the level of H₂O₂. As stress intensity raised (duration of treatment and Pb²⁺ concentration), so did the activities of superoxide dismutases, catalase and ascorbate peroxidase antioxidative enzymes and of low-molecular antioxidants, particularly glutathione (GSH), homoglutathione (h-GSH) and cysteine substrate toward their synthesis. The root cells redox state (GSH/GSSG) dropped proportionally to lead stress intensity.     

Joint genetic and network analyses identify loci associated with root growth under NaCl stress in Arabidopsis thaliana

Plants have evolved a series of tolerance mechanisms to saline stress, which perturbs physiological processes throughout the plant. To identify genetic mechanisms associated with salinity tolerance, we performed linkage analysis and genome‐wide association study (GWAS) on maintenance of root growth of Arabidopsis thaliana in hydroponic culture with weak and severe NaCl toxicity. The top 200 single‐nucleotide polymorphisms (SNPs) determined by GWAS could cumulatively explain approximately 70% of the variation observed at each stress level. The most significant SNPs were linked to the genes of ATP‐binding cassette B10 and vacuolar proton ATPase A2. Several known salinity tolerance genes such as potassium channel KAT1 and calcium sensor SOS3 were also linked to SNPs in the top 200. In parallel, we constructed a gene co‐expression network to independently verify that particular groups of genes work together to a common purpose. We identify molecular mechanisms to confer salt tolerance from both predictable and novel physiological sources and validate the utility of combined genetic and network analysis. Additionally, our study indicates that the genetic architecture of salt tolerance is responsive to the severity of stress. These gene datasets are a significant information resource for a following exploration of gene function.     

Influence of salt marsh on bacterial activity in two estuaries with different hydrodynamic characteristics (Ria de Aveiro and Tagus Estuary)

The influence of salt marsh on estuarine bacterioplankton was investigated in two estuaries with different hydrodynamic characteristics (Ria de Aveiro and Tagus Estuary). In the Ria de Aveiro, bacteria in the flood water overlying the marsh were two times more abundant and five to six times more active than in the main channel. In the Tagus Estuary, bacterial abundance was similar in flooding and channel water, but bacterial activity was up to two times higher in the main channel. The two salt marshes have distinct influences on estuarine bacterioplankton abundance and activity. In the Ria de Aveiro, salt marsh enhanced estuarine bacterial communities, increasing their size and stimulating their activity. By contrast, the salt marsh in the Tagus Estuary does not seem to increase the bacterial abundance and production in the channel water. These distinct influences may be explained by the hydrodynamic characteristics of the salt marshes, which were confirmed by the hydrodynamic model implemented for both systems.     

Comparative salt tolerance of two wild Hordeum species (H. maritimum with. and H. murinum L.) from the coast of Tuscany (Italy)

ABSTRACT

The differences in salt tolerance between Hordeum maritimum and H. murinum were studied. Seeds were collected at horn maturity from wild populations growing respectively near the Orbetello Lagoon and S. Piero a Grado (Tuscany, Italy) and were used in germination and growth tests at increasing salinity (NaCl) levels. H. maritimum was confirmed to be a true halophyte as compared to H. murinum, which exhibited germination behavior typical of many wild glycophytes. The higher salt sensitivity of H. murinum compared to H. maritimum was also shown by its shoot length values, which decreased only in H. murinum, albeit in 100 mM NaCl treatment. The higher degree of salt tolerance of H. maritimum is further demonstrated by the Na : K ratio. H. maritimum can accumulate a greater amount of sodium than potassium in both roots and shoots, even in the absence of salt treatment. However, in NaCl solutions H. maritimum showed a higher Na : K ratio for shoots — an index of better uptake and translocation of sodium to leaves — as has been demonstrated for many halophyte includers. These results thus help to enhance knowledge on wild relatives of barley, whose potential contribution to genetic improvement in salinity tolerance has previously not been thoroughly explored.     

Global regulation of reactive oxygen species scavenging genes in alfalfa root and shoot under gradual drought stress and recovery

Reactive oxygen species (ROS) production and scavenging in plants under drought stress have been studied intensively in recent years. Here we report a global analysis of gene expression for the major ROS generating and scavenging proteins in alfalfa root and shoot under gradual drought stress followed by one-day recovery. Data from two alfalfa varieties, one drought tolerant and one drought sensitive, were compared and no qualitative differences in ROS gene regulation between the two were found. Conserved, tissue-specific patterns of gene expression in response to drought were observed for several ROS-scavenging gene families, including ascorbate peroxidase, monodehydroascorbate reductase, and peroxiredoxin. In addition, differential gene expression within families was observed. Genes for the ROS-generating enzyme, NADPH oxidase were generally induced under drought, while those for glycolate oxidase were repressed. Among the ROS-scavenging protein genes, Ferritin, Cu/Zn superoxide dismutase (SOD), and the majority of the glutathione peroxidase family members were induced under drought in both roots and shoots of both alfalfa varieties. In contrast, Fe-SOD, CC-type glutaredoxins, and thoiredoxins were downregulated.