外源水杨酸对氯化钠胁迫下番茄幼苗糖代谢的影响

采用营养液水培法,用100、300和500 mg·L^-1不同浓度的水杨酸（SA）处理‘辽园多丽’番茄幼苗,测定在NaCl胁迫下番茄幼苗叶片果糖、葡萄糖、蔗糖含量和蔗谢代谢相关酶活性（酸性转化酶AI、中性转化酶NI、蔗糖磷酸合成酶SPS、蔗糖合成酶活性SS）的变化.结果表明：SA处理叶片可以维持或提高NaCl胁迫条件下番茄幼苗叶片果糖、葡萄糖含量及AI、NI、SPS和SS活性,其最高值分别比单纯NaCl处理植株增加30.0%、31.1%、24.7%、27.9%、22.0%和24.5%;但对NaCl胁迫条件下番茄幼苗叶片蔗糖含量的影响不大.表明水杨酸可以通过提高NaCl胁迫下番茄叶片转化酶活性来提高番茄叶片果糖和葡萄糖含量,从而缓解NaCl胁迫对番茄的伤害,其中以500 mg·L^-1的SA处理效果较理想.     

Effects of salicylic acid on the photosystem 2 of barley seedlings under osmotic stress

The effects of exogenous salicylic acid (SA) on photosystem 2 (PS 2) in barley (Hordeum vulgare L.) seedlings were investigated. SA pretreatment provided protection against subsequent osmotic stress. The highest protective effect of 0.25 mM SA was confirmed by determination of chlorophyll fluorescence, electrolyte leakage, malonyldialdehyde contents, PS 2 mRNAs and proteins. SA pretreatment increased reactive oxygen species (ROS), decreased net photosynthetic rate and stomatal conductance immediately, but prevented ROS accumulation during subsequent osmotic stress by activating antioxidant enzymes. Elimination of H₂O₂ during SA pretreatment inhibited almost all above mentioned SA effects. Therefore, SA pretreatment enhanced osmotic stress tolerance in barley seedlings mainly through ROS signals, rather than SA itself. The only SA-dependent and ROS-independent effect of exogenous SA on PS 2 was reduction of non-photochemical quenching.     

水杨酸对NaCl胁迫下菊芋幼苗光合作用及离子吸收的影响

为探明水杨酸(SA)对NaCl胁迫下菊芋耐盐生理的调控作用,研究了100μmol·L-1水杨酸对不同浓度NaCl胁迫下菊芋幼苗光合响应特征及离子吸收运输的影响.结果表明:施用水杨酸不仅能够有效缓解NaCl胁迫对菊芋光合作用的抑制,促进NaCl胁迫下菊芋幼苗各种光合色素含量、净光合速率、蒸腾速率、气孔导度和水分利用效率的增加,降低细胞间隙CO2浓度,同时也能明显降低NaCl胁迫下菊芋体内Na+的积累,促进菊芋幼苗对K+和Ca2+的吸收和向上运输,其中在100 mmol·L-1 NaCl处理下施用水杨酸处理的菊芋叶片中K+和Ca2+含量分别比未施用水杨酸处理增加了12.9％和14.7％,而Na+含量则降低了30.6％.由此证明,一定浓度外源水杨酸的施用有利于促进NaCl胁迫下菊芋幼苗光合功能的改善,以及有效维持菊芋幼苗体内矿质营养元素含量平衡,从而增强菊芋对NaCl胁迫的抗性,提高NaCl胁迫下的生产力.     

Alleviating the adverse effects of NaCl stress in maize seedlings by pretreating seeds with salicylic acid and 24-epibrassinolide

The effects of bio-regulators salicylic acid (SA) and 24-epibrassinolide (EBL) as seed soaking treatment on the growth traits, content of photosynthetic pigments, proline, relative water content (RWC), electrolyte leakage percent (EC%), antioxidative enzymes and leaf anatomy of Zea mays L. seedlings grown under 60 or 120 mM NaCl saline stress were studied. A greenhouse experiment was performed in a completely randomized design with nine treatments [control (treated with tap water); 60 mM NaCl; 120 mM NaCl; 10^− 4 M SA; 60 mM NaCl + 10^− 4 M SA; 120 mM NaCl + 10^− 4 M SA; 10 μM EBL; 60 mM NaCl + 10 μMEBL or 120 mM NaCl + 10 μM EBL] each with four replicates. The results indicated that NaCl stress significantly reduced plant growth traits, leaf photosynthetic pigment, soluble sugars, RWC%, and activities of catalase (CAT), peroxidase (POX) as well as leaf anatomy. However, the application of SA or EBL mitigated the toxic effects of NaCl stress on maize seedlings and considerably improved growth traits, photosynthetic pigments, proline, RWC%, CAT and POX enzyme activities as well as leaf anatomy. This study highlights the potential ameliorative effects of SA or EBL in mitigating the phytotoxicity of NaCl stress in seeds and growing seedlings.     

Protection against heat stress-induced oxidative damage in Arabidopsis involves calcium, abscisic acid, ethylene, and salicylic acid

Plants, in common with all organisms, have evolved mechanisms to cope with the problems caused by high temperatures. We examined specifically the involvement of calcium, abscisic acid (ABA), ethylene, and salicylic acid (SA) in the protection against heat-induced oxidative damage in Arabidopsis. Heat caused increased thiobarbituric acid reactive substance levels (an indicator of oxidative damage to membranes) and reduced survival. Both effects required light and were reduced in plants that had acquired thermotolerance through a mild heat pretreatment. Calcium channel blockers and calmodulin inhibitors increased these effects of heating and added calcium reversed them, implying that protection against heat-induced oxidative damage in Arabidopsis requires calcium and calmodulin. Similar to calcium, SA, 1-aminocyclopropane-1-carboxylic acid (a precursor to ethylene), and ABA added to plants protected them from heat-induced oxidative damage. In addition, the ethylene-insensitive mutant etr-1, the ABA-insensitive mutant abi-1, and a transgenic line expressing nahG (consequently inhibited in SA production) showed increased susceptibility to heat. These data suggest that protection against heat-induced oxidative damage in Arabidopsis also involves ethylene, ABA, and SA. Real time measurements of cytosolic calcium levels during heating in Arabidopsis detected no increases in response to heat per se, but showed transient elevations in response to recovery from heating. The magnitude of these calcium peaks was greater in thermotolerant plants, implying that these calcium signals might play a role in mediating the effects of acquired thermotolerance. Calcium channel blockers and calmodulin inhibitors added solely during the recovery phase suggest that this role for calcium is in protecting against oxidative damage specifically during/after recovery.     

The plant cuticle is required for osmotic stress regulation of abscisic acid biosynthesis and osmotic stress tolerance in Arabidopsis

Osmotic stress activates the biosynthesis of abscisic acid (ABA). One major step in ABA biosynthesis is the carotenoid cleavage catalyzed by a 9-cis epoxycarotenoid dioxygenase (NCED). To understand the mechanism for osmotic stress activation of ABA biosynthesis, we screened for Arabidopsis thaliana mutants that failed to induce the NCED3 gene expression in response to osmotic stress treatments. The ced1 (for 9-cis epoxycarotenoid dioxygenase defective 1) mutant isolated in this study showed markedly reduced expression of NCED3 in response to osmotic stress (polyethylene glycol) treatments compared with the wild type. Other ABA biosynthesis genes are also greatly reduced in ced1 under osmotic stress. ced1 mutant plants are very sensitive to even mild osmotic stress. Map-based cloning revealed unexpectedly that CED1 encodes a putative α/β hydrolase domain-containing protein and is allelic to the BODYGUARD gene that was recently shown to be essential for cuticle biogenesis. Further studies discovered that other cutin biosynthesis mutants are also impaired in osmotic stress induction of ABA biosynthesis genes and are sensitive to osmotic stress. Our work demonstrates that the cuticle functions not merely as a physical barrier to minimize water loss but also mediates osmotic stress signaling and tolerance by regulating ABA biosynthesis and signaling.     

Endogenous salicylic acid protects rice plants from oxidative damage caused by aging as well as biotic and abiotic stress

Salicylic acid (SA) is a key endogenous signal that mediates defense gene expression and disease resistance in many dicotyledonous species. In contrast to tobacco and Arabidopsis, which contain low basal levels of SA, rice has two orders of magnitude higher levels of SA and appears to be insensitive to exogenous SA treatment. To determine the role of SA in rice plants, we have generated SA-deficient transgenic rice by expressing the bacterial salicylate hydroxylase that degrades SA. Depletion of high levels of endogenous SA in transgenic rice does not measurably affect defense gene expression, but reduces the plant's capacity to detoxify reactive oxygen intermediates (ROI). SA-deficient transgenic rice contains elevated levels of superoxide and H2O2, and exhibits spontaneous lesion formation in an age- and light-dependent manner. Exogenous application of SA analog benzothiadiazole complements SA deficiency and suppresses ROI levels and lesion formation. Although an increase of conjugated catechol was detected in SA-deficient rice, catechol does not appear to significantly affect ROI levels based on the endogenous catechol data and exogenous catechol treatment. When infected with the blast fungus (Magnaporthe grisea), SA-deficient rice exhibits increased susceptibility to oxidative bursts elicited by avirulent isolates. Furthermore, SA-deficient rice is hyperresponsive to oxidative damage caused by paraquat treatment. Taken together, our results strongly suggest that SA plays an important role to modulate redox balance and protect rice plants from oxidative stress.     

Evidence for a predominant role of oxidative damage in germline mutation in mammals

Spontaneous copying errors in replication often are assumed to be the main source of germline mutations in humans and other mammals. However, when laboratory data on context-dependent patterns of oxidative DNA damage are compared with patterns of mutation inferred from mammalian sequence evolution, the strength of the correlation suggests that damage is the main source of mutations. Analysis of damage susceptibility holds promise for improving models of mutational specificity.     

Changes in antioxidant enzymes activity and oxidative stress by abscisic acid and salicylic acid in wheat genotypes

Abscisic acid (ABA) and salicylic acid (SA) were sprayed on leaves of wheat genotypes C 306 and Hira at 25 and 40 d after sowing under moderate water stress (−0.8 MPa) imposed by adding PEG-6000 in nutrient solution. ABA and SA increased the activities of superoxide dismutase, ascorbate peroxidase, glutathione reductase, and catalase in comparison to unsprayed control plants. Both ABA and SA treatments decreased the contents of hydrogen peroxide and thiobarbituric acid reactive substances, a measure of lipid peroxidation, compared to unsprayed plants. The beneficial effect of increase in antioxidant enzymes activity and decrease in oxidative stress was reflected in increase in chlorophyll and carotenoid contents, relative water content, membrane stability index, leaf area and total biomass over control plants. The lower concentrations of ABA (0.5 mM) and SA (1.0 mM) were generally more effective than higher concentrations.     

外源SA和NO对NaCl胁迫下番茄幼苗生长、光合及离子分布的影响

以番茄(Lycopersicon esculentum Mill.)品种‘秦丰保冠’为试材,采用营养液培养法,研究单独和复配施用外源水杨酸(SA)、一氧化氮(NO)供体硝普钠(SNP)对100mmol/L NaCl胁迫下番茄幼苗生长、光合及离子分布的影响。结果表明:(1)单独和复配外施SA、SNP均能有效抑制NaCl胁迫下番茄幼苗叶片光合色素(Chla、Chlb、Chla+b和Car)含量、Chla/b值、净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)、瞬时水分利用效率(WUEt)、表观光能利用效率(LUEapp)和表观CO2利用效率(CUEapp)的下降及Car/Chla+b值和胞间CO2浓度(Ci)的升高,并以SA和SNP复配处理效果最明显。(2)NaCl胁迫下,外源SA、SNP单独和复配处理的番茄幼苗各器官(叶、茎和根)中Cl-、Na+含量和Na+/K+、Na+/Ca2+、Na+/Mg2+值显著降低,而K+、Ca2+和Mg2+的含量却不同程度提高,其中以SA和SNP复配处理效果最好。(3)单独和复配外施SA、SNP均能有效减轻NaCl胁迫对番茄幼苗生长的抑制作用,并促进各器官生物量的积累和壮苗的形成,且以SA和SNP复配处理效果更佳。研究表明,复配外施SA和SNP在诱导番茄幼苗提高抗(耐)盐能力方面具有协同增效作用。     

A role for salicylic acid and NPR1 in regulating cell growth in Arabidopsis

Salicylic acid (SA) plays a key role in activating defenses and cell death during plant-pathogen interactions. In response to some pathogens, SA also limits the extent of cell death, indicating that it acts positively or negatively depending on the host-pathogen interaction. In addition, we previously showed that SA affects cell growth in the Arabidopsis defense-related mutants accelerated cell death 6-1 (acd6-1) and aberrant growth and death 2 (agd2). Using acd6-1, agd2 and two other defense-related mutants, lesion simulating disease 6 (lsd6), suppressor of SA-insensitivity (ssi1), we show here in detail that SA regulates cell growth by specifically affecting cell enlargement, endoreduplication and/or cell division. We find that SA can act either positively or negatively to regulate cell growth depending on the context in which signaling occurs. Additionally, Nonexpressor of PR 1 (NPR1), a key SA signaling protein important for regulating defenses and cell death, also acts to promote cell division and/or suppress endoreduplication during leaf development. We propose that SA interacts with multiple receptors or signaling pathways to control cellular alterations during normal development, pathogen attack and/or stress situations. We suggest that SA and NPR1 play broader roles in cell fate control than has previously been understood.     

外源NO和SA对盐胁迫下番茄幼苗叶片膜脂过氧化及AsA-GSH循环的影响

以番茄(Lycopersicon esculentum Mill.)品种‘秦丰保冠’为试材,在水培条件下研究单独和复配施用一氧化氮(NO)供体硝普钠(SNP)、水杨酸(SA)对100 mmol/L NaCl胁迫下番茄幼苗的生长、叶片光合作用、膜脂过氧化及抗坏血酸-谷胱甘肽(AsA-GSH)循环的影响。结果显示,盐胁迫能显著影响番茄幼苗的生长、光合作用和活性氧代谢系统的相关指标。单独或复配施用SNP、SA均能有效缓解番茄幼苗的盐渍伤害,并以SNP和SA复配处理效果最好。处理3~7 d时,叶片PSⅡ最大光化学效率(Fv/Fm)、净光合速率(Pn)、APX、GR、DHAR的活性、AsA和GSH含量分别较胁迫处理有不同程度的提高;而H2O2、MDA、DHA、GSSG的含量和电解质渗漏率分别较胁迫处理有不同程度的降低。研究结果表明盐胁迫下外源NO、SA单独或复配处理均能通过维持或协调作用促进番茄相关抗氧化酶活性的提高和抑制抗氧化剂含量的降低,起到维持AsA-GSH循环高效运转、减轻膜脂过氧化、促进光合作用、改善植株生长发育和提高幼苗盐渍抗性的作用,且NO和SA复配处理时具有协同增效的作用。     

Nickel-induced oxidative stress and the role of antioxidant defence in rice seedlings

Seedlings of rice (Oryza sativa L.) cv. Pant-12 grown in sand cultures containing 200 and 400 μM NiSO₄, showed a decrease in length and fresh weight of roots and shoots. Nickel was readily taken up by rice seedlings and the concentration was higher in roots than shoots. Nickel-treated seedlings showed increased rates of superoxide anion (O₂ ^•− ) production, elevated levels of H₂O₂ and thiobarbituric acid reactive substances (TBARS) demonstrating enhanced lipid peroxidation, and a decline in protein thiol levels indicative of increased protein oxidation compared to controls. With progressively higher Ni concentrations, non-protein thiol and ascorbate (AsA) increased, whereas the level of low-molecular-weight thiols (such as glutathione and hydroxyl-methyl glutathione), the ratio of these thiols to their corresponding disulphides, and the ratio of AsA to dehydroascorbic acid declined in the seedlings. Among the antioxidant enzymes studied, the activities of all isoforms of superoxide dismutase (Cu-Zn SOD, Mn SOD and Fe SOD), guaiacol peroxidases (GPX) and ascorbate peroxidase (APX) increased in Ni-treated seedlings, while no clear alteration in catalase activity was evident. Activity of the ascorbate-glutathione cycle enzymes monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and glutathione reductase (GR)—significantly increased in Ni-treated seedlings. However such increase was apparently insufficient to maintain the intracellular redox balance. Results suggest that Ni induces oxidative stress in rice plants, resulting in enhanced lipid peroxidation and decline in protein thiol levels, and that (hydroxyl-methyl) glutathione and AsA in conjunction with Cu-Zn SOD, GPX and APX are involved in stress response.     

Evidence for regulation of resistance in Arabidopsis to Egyptian cotton worm by salicylic and jasmonic acid signaling pathways

Signaling cross-talk between wound- and pathogen-response pathways influences resistance of plants to insects and disease. To elucidate potential interactions between salicylic acid (SA) and jasmonic acid (JA) defense pathways, we exploited the availability of characterized mutants of Arabidopsis thaliana (L.) Heynh. and monitored resistance to Egyptian cotton worm (Spodoptera littoralis Boisd.; Lepidoptera: Noctuidae). This generalist herbivore is sensitive to induced plant defense pathways and is thus a useful model for a mechanistic analysis of insect resistance. As expected, treatment of wild-type Arabidopsis with JA enhanced resistance to Egyptian cotton worm. Conversely, the coil mutant, with a deficiency in the JA response pathway, was more susceptible to Egyptian cotton worm than wild-type Arabidopsis. By contrast, the nprl mutant, with defects in systemic disease resistance, exhibited enhanced resistance to Egyptian cotton worm. Pretreatment with SA significantly reduced this enhanced resistance of nprl plants but had no influence on the resistance of wild-type plants. However, exogenous SA reduced the amount of JA that Egyptian cotton worm induced in both npr1 mutant and wild-type plants. Thus, this generalist herbivore engages two different induced defense pathways that interact to mediate resistance in Arabidopsis.     

Amelioration of NaCl stress by triadimefon in peanut seedlings

Peanut (Arachis hypogaea L.cv. VRI-2) seeds were imbibed in distilled water(control), 30 mM NaCl (stressed) and 30 mM NaCl + 10 mg L^-1 triadimefon for 12 h and grown in a seed germinator with a day/night temperature of 30/22 °C and a photoperiod of 16 h with a PPFD of 250 µEm^-2 s_-1. Seedlings were irrigated with respective treatment solutions. Fifteen days old seedlings were harvested and used for the study. The NaCl stress decreased seedling growth, dry weight, photosynthetic pigments, protein content and the level of proline oxidase activity and it increased proline, glycine betaine content, protease and ATPase activities. Triadimefon treatment ameliorated the stress caused NaCl by increasing root growth, dry weight, chlorophyll, carotenoid, protein and glycine betaine contents and by decreasing proline accumulation, proline oxidase levels and ATPase. The stress amelioration conferred by triadimefon may be mediated by increased protein synthesis, osmoregulation and reduced energy requirement.     

The microfilament cytoskeleton plays a vital role in salt and osmotic stress tolerance in Arabidopsis

Although recent studies have suggested that the microfilament (MF) cytoskeleton of plant cells participates in the response to salt stress, it remains unclear as to whether the MF cytoskeleton actually plays an active role in a plant's ability to withstand salt stress. In the present study, we report for the first time the role of MFs in salt tolerance of Arabidopsis thaliana . Our experiments revealed that Arabidopsis seedlings treated with 150 m m NaCl maintained MF assembly and bundle formation, whereas treatment with 250 m m NaCl initially induced MF assembly but subsequently caused MF disassembly. A corresponding change in the fluorescence intensity of MFs was also observed; that is, a sustained rise in fluorescence intensity in seedlings exposed to 150 m m NaCl and an initial rise and subsequent fall in seedlings exposed to 250 m m NaCl. These results suggest that MF assembly and bundles are induced early after salt stress treatment, while MF polymerization disappears after high salt stress. Facilitation of MF assembly with phalloidin rescued wild-type seedlings from death, whereas blocking MFs assembly with latrunculin A and cytochalasin D resulted in few survivors under salt stress. Pre-treatment of seedlings with phalloidin also clearly increased plant ability to withstand salt stress. MF assembly increased survival of Arabidopsis salt-sensitive sos2 mutants under salt stress and rescued defective sos2 mutants. Polymerization of MFs and its role in promoting survival was also found in plants exposed to osmotic stress. These findings suggest that the MF cytoskeleton participates and plays a vital role in responses to salt and osmotic stress in Arabidopsis .     

The alternative pathway in cucumber seedlings under low temperature stress was enhanced by salicylic acid

The alternative pathway is a cyanide-resistant and non-phosphorylatory electron transport pathway in mitochondria of higher plants. Alternative oxidase (AOX) is the terminal oxidase of this pathway. Our present study investigated the effect of exogenous salicylic acid (SA) on alternative pathway in cucumber (Cucumis sativus L.) seedlings under low temperature stress. Results showed that during the process of low temperature stress, the alternative pathway capacity was enhanced as AOX expression increased in SA pretreated seedlings. Compared with seedlings without SA pretreatment, slower decrease of relative water content and lower levels of electrolyte leakage, H₂O₂ and malonyldialdehyde content were detected in SA pretreated seedlings. These results indicated that SA could alleviate the injury caused by low temperature on cucumber seedlings. Since the special protective functions of alternative pathway and AOX in plants, we suggested that the alternative pathway was related to SA-mediated plant resistance to environmental stresses such as low temperature.