EGTA和La~(3 )对几种逆境诱导辣椒样半萜环化酶基因表达的影响

用钙离子螯合剂EGTA及细胞膜钙离子通道拮抗剂La3 预处理辣椒叶片 ,以破坏辣椒叶片中的钙信使系统 ,再用紫外线、CuCl2 、HgCl2 处理辣椒叶片 ,研究表明EGTA和La3 预处理未能降低CuCl2 、HgCl2 、UV诱导辣椒倍半萜环化酶活化的作用 ,EGTA预处理反而对CuCl2 、HgCl2 、UV的诱导辣椒倍半萜环化酶活性作用有一定的促进效应 .单独用EGTA处理也能诱导离体辣椒叶片表现出倍半萜环化酶活性 .NorthenBlot分析结果表明 ,EGTA能诱导辣椒倍半萜环化酶基因转录 .研究表明 ,在辣椒倍半萜环化酶基因表达过程中 ,还存在钙信使系统以外的信号传递途径 ;非生物诱发因子对倍半萜环化酶基因表达诱导作用与生物Elicitor的诱导作用在信号传递上有差异 .     

EGTA和La3+对几种逆境诱导辣椒样半萜环化酶基因表达的影响

用钙离子螯合剂EGTA及细胞膜钙离子通道拮抗剂La³⁺预处理辣椒叶片,以破坏辣椒叶片中的钙信使系统,再用紫外线、CuCl₂、HgCl₂处理辣椒叶片,研究表明EGTA和La³⁺预处理未能降低CuCl₂、HgCl₂、UV诱导辣椒倍半萜环化酶活化的作用,EGTA预处理反而对CuCl₂、HgCl₂、UV的诱导辣椒倍半萜环化酶活性作用有一定的促进效应.单独用EGTA处理也能诱导离体辣椒叶片表现出倍半萜环化酶活性.Northen Blot分析结果表明,EGTA能诱导辣椒倍半萜环化酶基因转录.研究表明,在辣椒倍半萜环化酶基因表达过程中,还存在钙信使系统以外的信号传递途径;非生物诱发因子对倍半萜环化酶基因表达诱导作用与生物Elicitor的诱导作用在信号传递上有差异.     

Cu2+作用下辣椒膜脂过氧化及倍半萜环化酶基因转录

分析了在CuCl2作用下辣椒叶片倍半萜环化酶活性,倍半萜环化酶mRNA表达,细胞GSH和GSSG代谢及膜脂过氧化,结果表明,Cu^2 能诱导辣椒叶片表达倍半萜环化酶活性,酶活性的表达与相应的基因转录有关,辣椒叶片在CuCl2作用下合成了含－SH的螯合肽,相应地GSH含量下降,GSSG的含量有所上升,细胞膜过氧化作用加剧,推测细胞膜脂过氧化产物或GSH氧化产物可能参与了CuCl2诱导辣椒倍半萜环化酶基因表达的信号传递作用。     

水杨酸对苦瓜叶片白粉病抗性及抗氧化酶活性的影响

以‘碧绿3号’苦瓜幼苗为材料,采用100、500和1000μmol.L-1的水杨酸(SA)溶液预处理后进行白粉菌的诱导接种,研究了SA处理对苦瓜叶片光合色素含量和4个抗氧化酶活性的影响。结果显示:各浓度SA处理苦瓜植株的病情指数均显著低于对照(蒸馏水处理),并随SA处理浓度增加而逐渐下降;各SA处理苦瓜叶片的光合色素含量均高于其对照,且随SA处理浓度升高而逐渐增加;苦瓜叶片APX、CAT和GR活性随SA处理浓度增加而升高,但GPX活性反而下降,各处理CAT和GR活性增幅均高于病情指数增幅,1000μmol.L-1SA处理的APX活性增幅也高于病情指数增幅。研究发现,SA处理可以提高苦瓜感染白粉病植株叶片的光合色素含量及其抗氧化酶活性,显著降低其病情指数,增强其白粉病抗性,且以1000μmol.L-1SA处理效果最好。     

Cu~(2 )作用下辣椒膜脂过氧化及倍半萜环化酶基因转录

分析了在ＣｕＣｌ２作用下辣椒叶片倍半萜环化酶活性、倍半萜环化酶ｍＲＮＡ表达、细胞ＧＳ Ｈ和ＧＳＳＧ代谢及膜脂过氧化。结果表明,Ｃｕ２＋能诱导辣椒叶片表达倍半萜环化酶活性,酶活性的表达与相应的基因转录有关。辣椒叶片在ＣｕＣｌ２作用下合成了含－ＳＨ的螯合肽,相应地ＧＳＨ含量下降,ＧＳＳＧ的含量有所上升,细胞膜脂过氧化作用加剧。推测细胞膜脂过氧化产物或ＧＳＨ氧化产物可能参与了ＣｕＣｌ２诱导辣椒倍半萜环化酶基因表达的信号传递作用。     

CO2和O3浓度升高及其复合作用对玉米（Zea mays L.）活性氧代谢及抗氧化酶活性的影响

为了揭示CO2和O3浓度升高及其复合作用对植物活性氧(ROS)代谢及抗氧化酶活性的影响机理,以玉米(Zea mays L.)为研究材料,利用开顶式气室(OTCs)研究了CO2和O3浓度升高及其复合作用下,玉米叶片活性氧产生速率、含量,膜脂过氧化程度,抗氧化酶活性,净光合速率及玉米籽粒产量的变化.结果表明,在整个生育期内,与对照相比,高浓度CO2((550±20)μmol · mol-1)处理下,玉米叶片净光合速率升高,O- ·2 产生速率、H2O2含量下降, MDA含量、相对电导率减小,SOD、CAT、POD活性增强,玉米百粒重和穗粒数增加;而在O3浓度为(80±10)nmol · mol-1的条件下,玉米叶片净光合速率下降,O- ·2 产生速率、H2O2含量升高,MDA含量、相对电导率增大,SOD、CAT、POD活性减弱,玉米百粒重和穗粒数降低;CO2和O3浓度升高复合((550±20)μmol · mol-1 (80±10)nmol · mol-1)处理下,玉米叶片的净光合速率、H2O2含量、SOD活性先升高后降低, MDA含量、相对电导率、CAT活性增加,POD活性减弱,而O- ·2 产生速率几乎不变化,且玉米的百粒重和穗粒数略低于对照.以上结果说明,CO2浓度升高抑制了玉米叶片活性氧的代谢速率,提高了抗氧化酶的活性,从而增强了光合作用,使玉米籽粒产量增加,对玉米表现为保护效应,而O3浓度升高促进了玉米叶片活性氧的代谢速率,降低了抗氧化酶的活性,抑制了光合作用,使玉米籽粒产量下降,对玉米表现为伤害效应.在CO2和O3浓度升高复合处理下,CO2浓度升高在一定程度上缓解了O3浓度升高对玉米的伤害效应,而O3浓度升高亦在一定程度上削弱了CO2浓度升高对玉米的保护效应.     

外源亚精胺对Hg2+胁迫下凤眼莲抗氧化系统的影响

通过Hoagland溶液培养实验,研究了外源亚精胺(Spd)(0.1 mmol?L-1)对Hg2+(0、10、20、30和40μmol?L-1)胁迫下凤眼莲叶片细胞内叶绿素、可溶性糖、可溶性蛋白含量及抗氧化系统的调节作用.结果显示,(1)随Hg2+处理浓度的升高,各处理凤眼莲叶片叶绿素a(Chl a)和叶绿素b(Chl b)含量均先升后降,并均在10μmol?L-1时达到最高值,但外源Spd处理组显著高于相应对照.(2)各处理凤眼莲叶片可溶性蛋白含量随Hg2+处理浓度的升高也呈先升后降趋势,而可溶性糖含量则呈持续上升趋势,但外源Spd处理亦明显高于相应对照.(3)随Hg2+处理浓度的升高,抗氧化物质AsA和GSH含量及抗氧化酶SOD、CAT、POD、APX及GR活性也均呈先升后降的变化趋势,而外源Spd处理植株的含量和活性均显著高于相应对照.(4)各处理凤眼莲叶片的H2O2、MDA含量及O2?-产生速率随Hg2+处理浓度的升高均持续上升,但在外源Spd处理后均比对照组下降.研究表明,Hg2+胁迫使凤眼莲生长受到严重伤害,外源Spd可大幅度地提高其抗氧化物质含量和保护酶活性,从而增强凤眼莲抗Hg2+胁迫的能力.     

O3和CO2浓度升高对油松针叶抗氧化系统的影响

利用开顶箱模拟大气O3与CO2浓度升高,对油松进行了连续4个月的熏蒸实验,探讨了油松针叶抗氧化系统化系统的响应.结果表明:1)高浓度O3显著增加了油松针叶过氧化氢的积累,到处理后期过量的过氧化氢显著地抑制了抗氧化酶活性,如SOD和APX,并且抗坏血酸被耗竭,加剧了膜质过氧化,最终导致了严重氧化伤害;2)高浓度CO2处理中油松针叶抗氧化酶活性普遍低于对照,ASA含量显著高于对照,可能是高CO2浓度促进ASA合成,或者是ASA的消耗减少,到处理后期使H2O2含量比对照降低了15.5%,从而减轻了膜质过氧化产物丙二醛含量,减轻了氧化伤害;3)与O3单因素相比,在协同处理中油松针叶具有较高的抗氧化酶活性和ASA含量,说明高CO2浓度减轻了高O3对抗氧化酶活性的抑制作用,并且提高了针叶内ASA含量,增强了针叶的抗氧化能力,有效地控制了ROS的产生与清除平衡,缓解了高O3带来的氧化伤害.     

土壤不同镉水平对马缨丹生长及其抗氧化酶活性的影响

采用盆栽试验方法,分别设置0(对照,不添加镉)、30、60、90、120、150、180、210mg·kg-1共8个土壤镉处理水平,研究土壤不同镉水平对马缨丹(Lantana comara L.)生长及其抗氧化酶活性的影响,以探讨马缨丹对镉胁迫的生理响应机制。结果显示:(1)随着土壤镉处理浓度的升高,马缨丹干重呈先升高后降低的趋势,30mg·kg-1镉处理能促进植株的生长,而浓度高于60mg·kg-1时显著抑制马缨丹的生长。(2)马缨丹叶片和根系中O-·2产生速率、H2O2和MDA含量及电解质渗漏率均随土壤镉处理浓度的升高和胁迫时间的延长逐渐升高,胁迫90d时,叶片和根系中O-·2产生速率、H2O2和MDA含量及电解质渗漏率分别在镉浓度高于60和30mg·kg-1时显著低于对照。(3)叶片和根系抗氧化酶SOD、POD、APX和CAT活性随着土壤镉处理浓度的增加大体呈先升高后降低的趋势,并在镉浓度分别高于90和60mg·kg-1时,叶片和根系抗氧化酶活性显著低于对照。研究表明,低浓度镉处理土壤能促进马缨丹植株生长,而高浓度镉处理土壤显著降低了马缨丹体内抗氧化酶活性,导致活性氧大量积累,引起严重的膜脂过氧化伤害,从而显著抑制马缨丹植株的生长。     

草酸诱导黄瓜幼苗对霜霉病的抗性与H2O2的关系

以长春密刺黄瓜幼苗为材料,对经草酸处理或霜霉菌接种后黄瓜叶片的过氧化物酶(POD)、超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性及H2O2含量的变化进行了研究.结果表明:草酸处理或霜霉菌接种均可诱导黄瓜幼苗叶片H2O2含量显著增加,且草酸预处理后接种的叶片比相应对照叶片能更快地积累H2O2;草酸处理后叶片SOD和POD活性均升高,而CAT活性却受到一定程度的抑制.研究发现,H2O2参与了幼苗对霜霉病的抗性诱导;叶片H2O2含量的增加与其SOD、POD活性升高、CAT活性下降有关;通过调节黄瓜叶片H2O2的含量来调控有关黄瓜霜霉病抗性的防御基因表达是草酸诱导抗性的机制之一.     

Involvement of Polyamine Oxidase in Abscisic Acid induced Cytosolic Antioxidant Defense in Leaves of Maize

Using pharmacological and biochemical approaches, the role of maize polyamine oxidase (MPAO) in abscisic acid (ABA)induced antioxidant defense in leaves of maize (Zea mays L.) plants was investigated. Exogenous ABA treatment enhanced the expression of the MPAO gene and the activities of apoplastic MPAO. Pretreatment with two different inhibitors for apoplastic MPAO partly reduced hydrogen peroxide (H2O2) accumulation induced by ABA and blocked the ABA-induced expression of the antioxidant genes superoxide dismutase 4 and cytosolic ascorbate peroxidase and the activities of the cytosolic antioxidant enzymes. Treatment with spermidine, the optimum substrate of MPAO, also induced the expression and the activities of the antioxidant enzymes, and the upregulation of the antioxidant enzymes was prevented by two inhibitors of MPAO and two scavengers of H2O2. These results suggest that MPAO contributes to ABA-induced cytosolic antioxidant defense through H2O2, a Spd catabolic product.     

Regulation of Antioxidant Enzymes by Salicylic Acid in Cucumber Leaves

Activities of the antioxidant enzymes involved in superoxide anion (O2-) and hydrogen peroxide (H2O2) metabolism were determined and the contents of O2 and 14202 were also measured. All concentrations of sahcylic acid (SA) tested (0.5, 1.0, 2.5 and 5.0 mmoL/L) significantly enhanced superoxide dismutase (SOD) and peroxidase (POD) activities not only in the first treated true leaf (leaf 1 ) but also in the second untreated true leaf (leaf 2) of Cucumis sativus L. When the leaves were treated with 1 mmol/L SA within 6 to 72 h, the activity of POD increased by 22 % to 67% in the treated leaf 1 and by 14% to 86% in the untreated leaf 2. However, no changes were observed during 3 h after treatment and at 96 h following treatment. Measurement of O2- and H202 showed that there was a significant decrease in 02' content and an increase in H202 content after SA treatment, but catalase (CAT) activity was only slighfiy inhibited and this suggested that the reason of the increase in H2O2 by SA treatment is not due to the inhibition of CAT but rather the increase in SOD activity. It was also found that SA at all concentrations tested could not induce new SOD isozyme but it induced 1 to 2 bands of new POD isozyme within one day after treatment. The results indicate that SA might involve in the regulation of antioxidant enzymes.     

Role of nitric oxide in abscisic acid-induced subcellular antioxidant defense of maize leaves

The sources of nitric oxide (NO) production in response to abscisic acid (ABA) and the role of NO in ABA-induced hydrogen peroxide (H(2)O(2)) accumulation and subcellular antioxidant defense in leaves of maize (Zea mays L.) plants were investigated. ABA induced increases in generation of NO and activity of nitric oxide synthase (NOS) in maize leaves. Such increases were blocked by pretreatment with each of the two NOS inhibitors. Pretreatments with a NO scavenger or NR inhibitors inhibited ABA-induced increase in production of NO, but did not affect the ABA-induced increases in activity of NOS, indicating that ABA-induced NO production originated from sources of NOS and NR. ABA- and H(2)O(2)-induced increases in expression of the antioxidant genes superoxide dismutase 4 (SOD4), cytosolic ascorbate peroxidase (cAPX), and glutathione reductase 1 (GR1) and the activities of the chloroplastic and cytosolic antioxidant enzymes were arrested by pretreatments with the NO scavenger, inhibitors of NOS and NR, indicating that NO is involved in the ABA- and H(2)O(2)-induced subcellular antioxidant defense reactions. On the other hand, NO donor sodium nitroprusside (SNP) reduced accumulation of H(2)O(2) induced by ABA, and c-PTIO reversed the effect of SNP in decreasing the accumulation of H(2)O(2). SNP induced increases in activities of subcellular antioxidant enzymes, and the increases were substantially prevented from occurring by the pretreatment with c-PTIO. These results suggest that ABA induces production of H(2)O(2) and NO, which can up-regulate activities of the subcellular antioxidant enzymes, to prevent overproduction of H(2)O(2) in maize plants. There is a negative feedback loop between NO and H(2)O(2) in ABA signal transduction in maize plants.     

Evidence of mitochondrial involvement in the transduction of signals required for the induction of genes associated with pathogen attack and senescence

Using the mRNA differential display technique, seven cDNAs have been isolated that are rapidly induced when cultured tobacco (Nicotiana tabacum) cells are treated with the mitochondrial electron transport inhibitor antimycin A (AA). Interestingly, six of the cDNAs show distinct similarity to genes known to be induced by processes that involve programmed cell death (PCD), such as senescence and pathogen attack. All of the cDNAs as well as Aox1, a gene encoding the alternative oxidase, were found to also be strongly induced by H2O2 and salicylic acid (SA). AA, H2O2 and SA treatment of tobacco cells caused a rapid rise in intracellular ROS accumulation that, when prevented by antioxidant treatment, resulted in inhibition of gene induction. Besides AA, both H2O2 and SA were found to disrupt normal mitochondrial function resulting in decreased rates of electron transport and a lowering of cellular ATP levels. Furthermore, the pre-treatment of tobacco cells with bongkrekic acid, a known inhibitor of the mitochondrial permeability transition pore in animal cells, was found to completely block gene induction when AA, H2O2 or SA were subsequently added. These findings suggest that the mitochondrion may serve an important role in conveying intracellular stress signals to the nucleus, leading to alterations in gene expression.     

Water stress-induced abscisic acid accumulation triggers the increased generation of reactive oxygen species and up-regulates the activities of antioxidant enzymes in maize leaves

The interrelationship among water-stress-induced abscisic acid (ABA) accumulation, the generation of reactive oxygen species (ROS), and the activities of several antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) was investigated in leaves of detached maize (Zea mays L.) plants exposed to -0.7 MPa water stress induced by polyethylene glycol (PEG 6000). Time-course analyses of ABA content, the production of ROS, and the activities of antioxidant enzymes in water-stressed leaves showed that a significant increase in the content of ABA preceded that of ROS, which was followed by a marked increase in the activities of these antioxidant enzymes. Pretreatment with an ABA biosynthesis inhibitor, tungstate, significantly suppressed the accumulation of ABA, and also reduced the increased generation of ROS and the up-regulation of these antioxidant enzymes in water-stressed leaves. A mild oxidative stress induced by paraquat, which generates O(2)(-) and then H(2)O(2), resulted in a significant enhancement in the activities of antioxidant enzymes in non-water-stressed leaves. Pretreatment with some ROS scavengers, such as Tiron and dimethylthiourea (DMTU), and an inhibitor of NAD(P)H oxidase, diphenyleneiodonium (DPI), almost completely arrested the increase in ROS and the activities of these antioxidant enzymes induced by water stress or ABA treatment. These data suggest that water stress-induced ABA accumulation triggers the increased generation of ROS, which, in turn, leads to the up-regulation of the antioxidant defence system.     

Role of salicylic acid in regulating ultraviolet radiation-induced oxidative stress in pepper leaves

The effect of salicylic acid (SA) counteracting the UV-A, UV-B, and UV-C-induced action on pepper (Capsicum annuum L.) plants was studied. For this purpose, the activities of antioxidant enzymes (peroxidase, polyphenol oxidase, ascorbate peroxidase, catalase, and glutathione reductase) were measured. Plants were sprayed with SA and treated with UV-A (320–390 nm), UV-B (312 nm), and UV-C (254 nm) radiation with a density of 6.1, 5.8, and 5.7 W/m². The activities of antioxidant enzymes were enhanced in leaves in response to UV-B and UV-C radiation. SA treatment moderated an increase in the activities of some antioxidant enzymes (peroxidase, ascorbate peroxidase, catalase, and glutathione reductase) in plants that were treated with UV radiation. The activity of antioxidant enzyme polyphenol oxidase in plants that were treated with UV-B, UV-C, and SA was significantly increased. The aim of the present study was to investigate the possible protective effect of SA treatment on UV-A, UV-B, and UV-C stress.     

Hydrogen peroxide generation by the pepper extracellular peroxidase CaPO2 activates local and systemic cell death and defense response to bacterial pathogens

Reactive oxygen species (ROS) are responsible for mediating cellular defense responses in plants. Controversy has existed over the origin of ROS in plant defense. We have isolated a novel extracellular peroxidase gene, CaPO2, from pepper (Capsicum annuum). Local or systemic expression of CaPO2 is induced in pepper by avirulent Xanthomonas campestris pv vesicatoria (Xcv) infection. We examined the function of the CaPO2 gene in plant defense using the virus-induced gene silencing technique and gain-of-function transgenic plants. CaPO2-silenced pepper plants were highly susceptible to Xcv infection. Virus-induced gene silencing of the CaPO2 gene also compromised hydrogen peroxide (H(2)O(2)) accumulation and hypersensitive cell death in leaves, both locally and systemically, during avirulent Xcv infection. In contrast, overexpression of CaPO2 in Arabidopsis (Arabidopsis thaliana) conferred enhanced disease resistance accompanied by cell death, H(2)O(2) accumulation, and PR gene induction. In CaPO2-overexpression Arabidopsis leaves infected by Pseudomonas syringae pv tomato, H(2)O(2) generation was sensitive to potassium cyanide (a peroxidase inhibitor) but insensitive to diphenylene iodonium (an NADPH oxidase inhibitor), suggesting that H(2)O(2) generation depends on peroxidase in Arabidopsis. Together, these results indicate that the CaPO2 peroxidase is involved in ROS generation, both locally and systemically, to activate cell death and PR gene induction during the defense response to pathogen invasion.     

外源水杨酸对低温下杏花抗氧化酶和CBF转录因子表达的影响

为探讨水杨酸（SA）对杏花抗寒性的影响机制,以早熟品种‘骆驼黄’杏的显蕾期花枝为试材,分析–2℃的低温下适宜浓度SA及其抑制剂ABT和PAC对杏花MDA、抗氧化酶和CBF转录因子的影响。结果表明,–2℃低温条件下,对照和2个SA抑制剂处理的杏花细胞膜系统均受到严重伤害,CAT、POD和SOD等抗氧化酶活性降低,MDA含量明显升高。而SA预处理的杏花在低温胁迫期间抗氧化酶活性增强,MDA含量比对照和抑制剂处理的有明显降低且相对稳定。通过荧光定量检测CBF转录因子的表达水平,表明SA能诱导杏花CBF基因的表达,尤其在低温处理3 h时,SA预处理的杏花中CBF的表达量明显高于对照和SA抑制剂处理。由此认为,适宜浓度的外源SA可能是通过调控低温下杏花中CBF转录因子的表达、增强细胞的抗氧化酶活性,减轻低温造成的膜脂过氧化伤害,从而在一定程度上增强了杏花的抗寒性。     

Salicylic acid negatively affects the response to salt stress in pea plants

We studied the effect of salicylic acid (SA) treatment on the response of pea plants to salinity. Sodium chloride (NaCl)-induced damage to leaves was increased by SA, which was correlated with a reduction in plant growth. The content of reduced ascorbate and glutathione in leaves of salt-treated plants increased in response to SA, although accumulation of the respective oxidised forms occurred. An increase in hydrogen peroxide also occurred in leaves of salt-exposed plants treated with SA. In the absence of NaCl, SA increased ascorbate peroxidase (APX; 100 μm) and glutathione-S transferase (GST; 50 μm) activities and increased catalase (CAT) activity in a concentration-dependent manner. Salinity decreased glutathione reductase (GR) activity, but increased GST and CAT activity. In salt-stressed plants, SA also produced changes in antioxidative enzymes: 100 μm SA decreased APX but increased GST. Finally, a concentration-dependent increase in superoxide dismutase (SOD) activity was induced by SA treatment in salt-stressed plants. Induction of PR-1b was observed in NaCl-stressed plants treated with SA. The treatment with SA, as well as the interaction between salinity and SA treatment, had a significant effect on PsMAPK3 expression. The expression of PsMAPK3 was not altered by 70 mm NaCl, but was statistically higher in the absence than in the presence of SA. Overall, the results show that SA treatment negatively affected the response of pea plants to NaCl, and this response correlated with an imbalance in antioxidant metabolism. The data also show that SA treatment could enhance the resistance of salt-stressed plants to possible opportunistic pathogen attack, as suggested by increased PR-1b gene expression.