- Original Article
- Open Access
Effects of volatile organic compound ether on cell responses and gene expressions in Arabidopsis
© Tseng and Lin. 2016
Received: 15 July 2015
Accepted: 27 October 2015
Published: 6 January 2016
The volatile organic compound ether is widely used as an industrial solvent and easily released to the environment. Our previous research indicated that ether triggers reactive oxygen species (ROS) production and activates ethylene biosynthetic genes and defense gene expressions in tomato. In the present study, we investigated the effect of ether on cell responses and gene expressions in Arabidopsis and compared the ROS and phytohormones produced in Arabidopsis and tomato plants in response to different air pollutants (O3 vs. ether).
Ether induced the sequential production of superoxide anion and hydrogen peroxide in Arabidopsis. Ether also triggered expressions of ethylene, salicylic acid and jasmonic acid biosynthetic genes. The temporal expression patterns of MAP kinase and protein phosphatase genes are in good accordance with those of the ethylene and salicylic acid biosynthetic genes, suggesting that induction of these phytohormone biosynthesis were through signaling pathways including both phosphorylation and/or dephosphorylation. By contrast, expression pattern of protein phosphatase PP2A3&4 coincided well with the expression of jasmonic acid biosynthetic gene LOX4, suggesting that induction of jasmonic acid biosynthesis is through PP2A3&4. However, the production of ROS and temporal expression patterns of phytohormone biosynthetic genes in Arabidopsis in response to ether were different from those to O3 and were different from those in tomato as well.
Different plants have different strategies to respond to the same abiotic stress, and each plant species possesses its own unique signaling pathways that regulate the responding process.
The deleterious effects of industrial air pollution on plants have been an issue due to the massive increase in fossil fuel combustion. Among the air pollutants, tropospheric ozone (O3) is considered the most phytotoxic, and there are many literature reports document the adverse effects of tropospheric O3 on crop yield, forest growth, and the metabolism and physiology of plants (Karnosky et al. 2007). In addition to ozone, the role of volatile organic compounds (VOC) as air pollutants has drawn much attention (Cape 2003). VOCs are carbon-based compounds that may contain oxygen, nitrogen, bromide and chloride atom and easily evaporate into the environment. The major sources of anthropogenic airborne VOCs are industrial processes, oil refining, fuel combustions, and vehicle exhaust emissions. Experimental studies have shown that some VOCs (e.g. acetate, formaldehyde, peroxyacetyl nitrate, and trichloroethylene.) are detrimental to vegetation, although most experiments investigated short-term exposures at high concentrations as opposed to ambient air conditions (Cape 2003). Cape (2003) prepared a review article, summarizing several studies on the effects of VOCs on vegetation at low concentrations, and long exposure times. VOCs may cause detrimental effects on leaves, flowering, seed production, protein content, plant metabolism, and total dry weight. Some countries publish emission inventories of VOCs, and take efforts to minimize VOC release into the environment. Despite a large body of research on the effects of O3 on plants at molecular and cellular levels, few reports describe the effects of VOCs on plants at the molecular and cellular levels.
For a period of time, the plants in our laboratory were polluted by diethyl ether (ether) that came from nearby chemical laboratory. Ether, a VOC, is widely used as an industrial solvent for waxes, fats, oils, perfumes, alkaloids, gums, and nitrocellulose, and also a solvent for hormone extraction from plant and animal tissues (Howard 1993). During its use as an industrial solvent and extractant, ether would easily release into the environment and evaporate into the atmosphere. Once in the vapor phase, it has very low chemical reactivity. Not absorbing light with wavelength longer than 290 nm, ether is not decomposed through photolysis (Howard 1993). However, ether can be photooxidized via vapor-phase reaction with photochemically produced hydroxyl radicals at a half-life of 29 h. Ether is not hydrolyzed or biodegraded in environmental media, so is persistent if released to soil or water. The compound is detectable in drinking water at water treatment plants, in the tap water in three out of ten North American cities, in drinking-water groundwater wells located downstream of municipal and industrial solid-waste landfill, and in the effluent of sewage treatment plants and chemical industries (Howard 1993). The detected concentrations range from 2.5–1000 μg/L.
In our previous research, we discovered that ether triggers a sequential production of superoxide anion (·O2 −) and hydrogen peroxide (H2O2), and specifically induces tomato 1-aminocyclopropane-1-carboxylic acid oxidase (LeACO1) and LeACO4 genes through distinct signaling pathways (Lin et al. 2011). While the LeACO1 gene was induced via protein phosphorylation (e.g. via MAP kinase), the LeACO4 was induced via protein dephosphorylation (e.g. via protein phosphatase). Furthermore, induction of ACO gene expression occurred simultaneously with ROS accumulation and coincided with the occurrence of cell death. Our study results suggest that the cellular responses of tomato plants to ether are different from the plant responses to O3, and that tomato plants respond to different air pollutants through different perceptions and downstream signaling pathways (Lin et al. 2011). These findings unveiled the complex signaling networks of plant response to different air pollutants.
The purpose of the present study is to elucidate how the model plant Arabidopsis responds to ether in the context of ROS production and phytohormone biosynthetic gene expressions. The results will be helpful in understanding how differently plants (tomato vs. Arabidopsis) respond to the same type of molecule, ether, and how plants respond to different air pollutants (O3 vs. ether).
Arabidopsis seeds (A. thaliana cv Columbia) were soaked in ddH2O at 4 °C for 3 days and sown in wet soil. Seven days later, the seedlings were transferred to pots and grown in a temperature- and lighting-controlled growth chamber at 22 °C at 16/8 h light/dark cycles. Twenty-five- to thirty-day old plants were used for all the experiments.
Ether fumigation and histochemical staining of ·O2 −, H2O2, and dead cells
For ether fumigation, twenty-five- to thirty-day old plants were exposed to ether (Sigma, MO, USA) with 500 μL/L in a 4 L can for various time intervals. Histochemical staining of · O2 −, H2O2, and dead cells were performed as described by Lin et al. (2011). Two Arabidopsis plants were exposed to 500 μL/L ether fumigation for each time point, and all the mature leaves were harvested for histochemical staining. The · O2 − production was detected by nitroblue tetrazolium (NBT) staining. The leaves were vacuum-infiltrated with 50 mL staining buffer [10 mM NaN3, 10 mM potassium phosphate buffer, pH7.8, and 0.1 % NBT] (Sigma, MO, USA) for 1 min and with a total of four times. The leaves were then incubated in the staining buffer in dark for 30 min. After staining, the leaves were cleared in boiling 70 % ethanol for 15 min. Production of · O2 − was directly visualized by forming blue formazan precipitate. The H2O2 production was detected by the 3,3′-diaminobenzidine tetrahydrochloride (DAB) staining. The whole plants were removed from soil and soaked in 100 mL DAB staining buffer [10 mM 2-(N-morpholino)-ethane sulfonic acid (MES), pH6.5, and 0.1 % DAB] (Sigma, MO, USA) for 10 h in the dark. Following staining, the leaves were cleared in boiling 70 % ethanol for 15 min. Production of H2O2 was visualized as a reddish-brown coloration. Dead cells in the mesophyll tissues were assessed by the Evans blue staining. The leaves were vacuum-infiltrated with 50 mL of 1 % (w/v) Evans blue (Sigma, MO, USA) staining buffer for 1 min with a total of four times and then incubated in the staining buffer in dark for 30 min. After staining, the leaves were cleared in boiling 70 % ethanol for 5 min. Dead cells were unable to exclude Evans blue and were stained deep blue. The samples were mounted on glass slides with 30 % glycerol and examined with a fluorescence microscope (Eclipse E600, Nikon, Japan). The mechanically wounded plants that were punched with a brush leaving 0.5–1 mm holes spaced 2 mm apart were used a positive control. The density of the brush hole is approximately 25 holes/cm2. The wounded plants were then incubated in growth chamber for 3 h before staining.
RNA extraction and real-time reverse transcription PCR (RT-PCR)
For RNA extraction, two plants were used for each time point and five to six mature leaves were collected. Total RNA was isolated from treated leaves using TRIzol™ reagent (Ambion, CA, USA) according to the manufacture’s protocol. Briefly, approximately 100 mg of leaves were homogenized with 1 mL of TRIzol reagent with a pestle. Two hundred microliters of chloroform were added to separate the RNA from cell pellets. The RNA was precipitated with 0.5 mL isopropanol. The RNA precipitates were washed with 70 % ethanol, air-dried, and resuspended with 20 μL DEPC-treated ddH2O. The concentration of RNA was determined by spectrophotometer. For cDNA synthesis, reverse transcription was performed in a 30 μL reaction volume containing 3 μg of the total RNA, 100 units of MMLV reverse transcriptase (Promega, WI, USA), 1X MMLV reaction buffer, 0.1 mM each of dNTPs (Thermo Scientific, MA, USA), and 1 μΜ oligo dT18 primer (Protech, Taipei, Taiwan). The reaction was carried out at 37 °C for 2 h. Real-time RT-PCR amplification of the cDNA clones were performed in a 10 μL reaction volume containing 2 μg of cDNA, 1X GoTaq™ qPCR Master Mix reagent (Promega, WI, USA), 1X CXR reference dye, and 0.2 μM of each primer (Additional file 1: Table S1). Thermocycling conditions were 95 °C for 2 min followed by 39 cycles of 95 °C for 15 s, 55 °C for 45 s, and 72 °C for 30 s, and a final 5 min at 72 °C on a CFX96™ real-time PCR detection system (Bio-Rad, USA). The amplified Arabidopsis Actin2 (ACT2) was used as an internal control. Relative gene expression levels were calculated with the 2−△△Ct method. Each value was the mean ± standard deviation of three independent experiments. The results were analyzed using Student’s t test. Differences of relative fold increase between the 0 min the other time points were considered statistically significant if P < 0.05 (*).
Detection of cell death and ROS generation in response to ether
Expressions of ROS producing and phytohormone biosynthetic genes in response to ether
Determination of signaling pathways in response to ether
Oxidative burst is a general response of plants to different air pollutants
Oxidative burst is a general response of sensitive plants to air pollutant O3 (Wohlgemuth et al. 2002). In tomato and tobacco, H2O2 is the major ROS produced in response to O3, and ethylene is involved in the amplification of ROS production and regulation of cell death (Moeder et al. 2002; Schraudner et al. 1998; Castagna et al. 2007). By contrast, ·O2 − is the major ROS produced in Arabidopsis in response to O3, and salicylic acid is responsible for cell death (Rao and Davis 1999). Our previous study showed that acute exposure of tomato plants to ether causes cell death and that ·O2 − was the major ROS produced in response to ether (Lin et al. 2011). In the present study, we detected a transient, sequential production of ·O2 − and H2O2 in Arabidopsis in response to ether, and no cell death observed, suggesting that Arabidopsis is not as susceptible to ether treatment as tomato is (Figs. 1, 2, 3). Expression patterns of ROS metabolizing genes such as RBOHD and CSD1 corresponded well with the histochemical observations of ROS accumulation. Production of RBOHD transcripts at 15 min after initiation of ether fumigation coincided well with the accumulation of ·O2 − at 30 min post-exposure (Figs. 2, 4). Diminution of ·O2 − at 30–60 min was accompanied by accumulation of H2O2 at 30–120 min (Figs. 2, 3). Furthermore, induction of CSD1 at 15–60 min was also in good accordance with the production of H2O2 (Figs. 3, 4). All these results suggested that ·O2 − and H2O2 were sequentially produced by RBOHD and CSD, respectively, in Arabidopsis in response to ether, and oxidative burst is a general response of plants to different air pollutants (Fig. 9).
Ascorbate is believed to provide important protection in the apoplast against O3-derived ROS (Castagna and Ranieri, 2009). In addition to direct reaction with ROS, ascorbate also acts as a reducing substrate for ascorbate peroxidase (APX), which scavenges H2O2 and thus affects the propagation of the O3 stress. However, in this study no induction of APX1 gene expression in ether-treated Arabidopsis suggested that ether-derived ROS were more likely to be quickly quenched by direct reaction with ascorbate or other antioxidant systems rather than by APX1 (Fig. 4).
Induction of salicylate and ethylene accumulation by ether does not suppress jasmonate biosynthesis
In O3-treated Arabidopsis, salicylic acid is the key signal in antioxidant response and in initiating O3-induced cell death in Arabidopsis (Rao and Davis 1999; Tamaoki 2008). O3 stimulates the production of ethylene via salicylic acid. Both salicylic acid and ethylene suppress jasmonic acid biosynthesis and act in concert to induce high levels of ·O2 − or ·O2 − together with H2O2, and the production of ROS finally leads to cell death (Rao and Davis 1999; Wohlgemuth et al. 2002). By contrast, in O3-treated tomato ethylene is the key factor that triggers the progression of O3-induced lesions (Castagna et al. 2007). Furthermore, O3 induce ethylene and jasmonate biosynthesis, although with different timings and to different extents. In the present study, ether stimulated expressions of salicylic biosynthetic gene, ICS, transcripts from 15–30 min, and the amount returned to basal level by 60 min post-exposure (Fig. 5). The transcript levels of ethylene biosynthetic genes, ACS6, ACO3, and ACO4, were also promptly accumulated at 15 min and began to decrease at 30 min (Fig. 5). Occurrence of ROS production and ethylene and salicylic acid biosynthesis at the very early stage of ether treatment suggested that these three events simultaneously occurred in response to ether (Figs. 2, 3, 4, 5). Furthermore, no cell death occurred during this time period or thereafter, suggesting that production of ROS and ethylene and salicylic acid biosynthesis in response to ether did not promote cell death as they do in Arabidopsis in response to O3.
We also detected an accumulation of jasmonic acid biosynthetic gene transcripts, LOX4, following exposure to ether for 15 min and maintaining at high level till 240 min, suggesting that ether also promptly induces jasmonic acid biosynthesis (Fig. 5). However, continuous induction of LOX4 gene at the time that ICS, ACS6, ACO3, and ACO4 gene expressions decreased in response to ether indicated that induction of salicylic acid and ethylene did not suppress the jasmonic acid biosynthesis as they do in response to O3 (Rao and Davis 1999; Wohlgemuth et al. 2002). Biosynthesis of jasmonic acid may inhibit the spread of cell death (Tuominen et al. 2004). Therefore, it is possible that continuous production of jasmonic acid suppressed the occurrence and spread of cell death during ether exposure.
We assayed five PR genes and found that the expression patterns of PR2, PR4, and PR5 were similar to those of the ethylene and salicylic acid biosynthetic genes (Figs. 5, 6). Expressions of SA-dependent PR1 and ethylene-dependent PR4 genes in Arabidopsis have been reported to be induced under O3 stress (Rao et al. 2002). The result of our previous study suggested that ethylene produced in tomato plants in response to ether activates expression of PR4 but not PR1 genes (Lin et al. 2011). Therefore, it is possible that expressions of these PR genes were induced by ethylene in Arabidopsis in response to ether (Fig. 9, dash lines). In addition, low dosage exposure to ROS may produce signaling effects on growth, development, stress acclimation, and pathogen responses (Foyer and Noctor 2005). Therefore, ether-generated ROS may play a role in signaling modulation and induce the expression of the PR genes (Fig. 9, dash lines). However, whether expressions of the PR genes were induced by ethylene or ROS signaling during ether fumigation remains unclear and needs further elucidation.
The ether responsive signaling pathways
The signal transduction pathways induced by O3 exposure have been extensively elucidated in Arabidopsis, whereas rare reports, if any, are focused on tomato. MPK3 and MPK6 in Arabidopsis are activated within 30–60 min in response to O3 (Ahlfors et al. 2004). Phosphorylation of ACS2 and ACS6 by MPK3 and MPK6 results in increased ethylene biosynthesis through protein stabilization (Liu and Zhang 2004; Han et al. 2010). Skottke et al. (2011) showed that PP2A mediates a finely tuned regulation of overall ethylene production by differentially affecting the stability of specific classes of ACS enzymes. Ludwików et al. (2014) showed that the Arabidopsis protein phosphatase type 2C is involved in the regulation of ethylene biosynthesis during ozone stress. In this study, the temporal expression patterns of MAP kinase and protein phosphatase genes were in good accordance with those of the hormone biosynthetic genes. The temporal expression patterns of ACS6, ACO3, ACO4 and ICS were in unanimity with the expression patterns of MAP kinase, MPK1, MPK3, MPK4, and MPK6, and protein phosphatase, MKP1, AP2C1, and PP2A1 (Figs. 5, 7, 8). They were all induced at 15–60 min, suggesting that MPK1, MPK3, MPK4, MPK6, MKP1, AP2C1, and PP2A1 were involved in protein phosphorylation/dephosphorylation leading to induction of ethylene and salicylic acid biosynthesis by ether (Fig. 9). Expression patterns of protein phosphatase PP2A3&4 coincided well with the expression of LOX4 (Figs. 5, 8). Both LOX4 and PP2A3&4 transcripts exhibited a biphasic accumulation pattern. Their transcript levels showed a quick rise at 15 min and reached a peak at 15–60 min, and the second peak was detected at 120–240 min post-exposure. The sequential expression of PP2A3&4 and LOX4 genes suggested that induction of jasmonic acid biosynthesis might be through phosphatase PP2A3&4 (Fig. 9). Although further experiments are required to confirm our model, ether induction of MAP kinase and protein phosphatase genes reinforces the idea that signaling events initiated by diverse biotic or abiotic stresses may converge at the point of MAP kinases and/or phosphatase (Farkas et al. 2007; Zhang et al. 2006).
In this study, ·O2 − and H2O2 were sequentially produced in Arabidopsis in response to ether, indicating that oxidative burst is a general response of plants to different air pollutants. Induction of salicylic acid and ethylene did not suppress the jasmonic acid biosynthesis as they do in response to O3 treatment, suggesting that plant responds differently to different air pollutants. The different ROS and hormones produced in Arabidopsis and tomato plants in response to different air pollutants (O3 vs. ether) suggested that different plants have different strategies to respond to the same abiotic stress, and each plant species possesses its own unique signaling pathways that regulate the responding process.
YTT designed and carried out the experiments, analyzed and interpreted data, and helped to draft the manuscript. KCL designed the experiments, analyzed and interpreted data, and drafted the manuscript. Both authors read and approved the final manuscript.
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
- Ahlfors R, Macioszek V, Rudd J, Brosché M, Schlichting R, Scheel D, Kangasjärvi J (2004) Stress hormone-independent activation and nuclear translocation of mitogen-activated protein kinases in Arabidopsis thaliana during ozone exposure. Plant J 40:512–522View ArticlePubMedGoogle Scholar
- Bannenberg G, Martínez M, Hamberg M, Castresana C (2008) Diversity of the enzymatic activity in the lipoxygenase gene family of Arabidopsis thaliana. Lipids 44:85–95View ArticlePubMedGoogle Scholar
- Cape JN (2003) Effects of airborne volatile organic compounds on plants. Environ Pollut 122:145–157View ArticlePubMedGoogle Scholar
- Castagna A, Ranieri A (2009) Detoxification and repair process of ozone injury: from O3 uptake to gene expression adjustment. Environ Pollut 157:1461–1469View ArticlePubMedGoogle Scholar
- Castagna A, Ederli L, Pasqualini S, Mensuali-Sodi A, Baldan B, Donnini S, Ranieri A (2007) The tomato ethylene receptor LE-ETR3 (NR) is not involved in mediating ozone sensitivity: causal relationships among ethylene emission, oxidative burst and tissue damage. New Phytol 174:342–356View ArticlePubMedGoogle Scholar
- Farkas I, Dombrádi V, Miskei M, Szabados L, Koncz C (2007) Arabidopsis PPP family of serine/threonine phosphatases. Trends Plant Sci 12:169–176View ArticlePubMedGoogle Scholar
- Foyer CH, Noctor G (2005) Oxidant and antioxidant signaling in plants: a re-evaluation of the concept of oxidative stress in a physiological context. Plant Cell Environ 28:1056–1071View ArticleGoogle Scholar
- Han L, Li GJ, Yang KY, Mao G, Wang R, Liu Y, Zhang S (2010) Mitogen-activated protein kinase 3 and 6 regulate Botrytis cinerea-induced ethylene production in Arabidopsis. Plant J 64:114–127PubMedGoogle Scholar
- Howard PH (1993) Handbook of environmental fate and exposure data for organic chemicals. Diethyl ether, vol Vol. IV. Lewis Publishers, Florida, pp 221–229Google Scholar
- Karnosky DF, Skelly JM, Percy KE, Chappelka AH (2007) Perspectives regarding 50 years of research on effects of tropospheric ozone air pollution on US forests. Environ Pollut 147:489–506View ArticlePubMedGoogle Scholar
- Lin KC, Sun PC, Lin PL (2011) Production of reactive oxygen species and induction of signaling pathways for the ACO gene expressions in tomato plants triggered by the volatile organic compound ether. Plant Cell Rep 30:599–611View ArticlePubMedGoogle Scholar
- Liu Y, Zhang S (2004) Phosphorylation of 1-aminocyclopropane-1-carboxylic acid synthase by MPK6, a stress-responsive mitogen-activated protein kinase, induces ethylene biosynthesis in Arabidopsis. Plant Cell 16:3386–3399View ArticlePubMedPubMed CentralGoogle Scholar
- Ludwików A, Cieśla A, Kasprowicz-Maluśki A, Mituła F, Tajdel M, Gałgański L, Ziółkowski PA, Kubiak P, Małecka A, Piechalak A, Szabat M, Górska A, Dąbrowski M, Ibragimow I, Sadowski J (2014) Arabidopsis protein phosphatase 2C ABI1 interacts with type I ACC syntheses and is involved in the regulation of ozone-induced ethylene biosynthesis. Mol Plant 7:960–976View ArticlePubMedGoogle Scholar
- Mishra NS, Tuteja R, Tuteja N (2006) Signaling through MAP kinase networks in plants. Arch Biochem Biophys 452:55–68View ArticlePubMedGoogle Scholar
- Moeder W, Barry CS, Tauriainen AA, Betz C, Tuomainen J, Utriainen M, Grierson D, Sandermann H, Langebartels C, Kangasjärvi J (2002) Ethylene synthesis regulated by biphasic induction of 1-aminocyclopropane-1-carboxylic acid synthase and 1-aminocyclopropane-1-carboxylic acid oxidase genes is required for hydrogen peroxide accumulation and cell death in ozone-exposed tomato. Plant Physiol 130:1918–1926View ArticlePubMedPubMed CentralGoogle Scholar
- Overmyer K, Brosché M, Kangasjärvi J (2003) Reactive oxygen species and hormonal control of cell death. Trends Plant Sci 8:335–342View ArticlePubMedGoogle Scholar
- Rao MV, Davis KR (1999) Ozone-induced cell death occurs via two distinct mechanisms in Arabidopsis: the role of salicylic acid. Plant J 17:603–614View ArticlePubMedGoogle Scholar
- Rao MV, Lee HI, Davis KR (2002) Ozone-induced ethylene production is dependent on salicylic acid, and both salicylic acid and ethylene act in concert to regulate ozone-induced cell death. Plant J 32:447–456View ArticlePubMedGoogle Scholar
- Schraudner M, Moeder W, Wiese C, Camp WV, Inzé D, Langebartels C, Sandermann H Jr (1998) Ozone-induced oxidative burst in the ozone biomonitor plant, tobacco Bel W3. Plant J 16:235–245View ArticlePubMedGoogle Scholar
- Schweighofer A, Kazanaviciute V, Scheikl E, Teige M, Doczi R, Hirt H, Schwanninger M, Kant M, Schuurink R, Mauch F, Buchala A, Cardinale F, Meskienea I (2007) The PP2C-type phosphatase AP2C1, which negatively regulates MPK4 and MPK6, modulates innate immunity, jasmonic acid, and ethylene levels in Arabidopsis. Plant Cell 19:2213–2224View ArticlePubMedPubMed CentralGoogle Scholar
- Skottke KR, Yoon GM, Kieber JJ, DeLong A (2011) Protein phosphatase 2A controls ethylene biosynthesis by differentially regulating the turnover of ACC synthase isoforms. PLoS Genet 7:e1001370. doi:10.1371/journal.pgen.1001370 View ArticlePubMedPubMed CentralGoogle Scholar
- Tamaoki M (2008) The role of phytohormone signaling in ozone-induced cell death in plants. Plant Signal Behav 3:166–174View ArticlePubMedPubMed CentralGoogle Scholar
- Tosti N, Pasqualini S, Borgogni A, Ederli L, Falistocco E, Crispi S, Paolocci F (2006) Gene expression profiles of O3-treated Arabidopsis plants. Plant Cell Environ 29:1686–1702View ArticlePubMedGoogle Scholar
- Tuominen H, Overmyer K, Keinänen M, Kollist H, Kangasjärvi J (2004) Mutual antagonism of ethylene and jasmonic acid regulates ozone-induced spreading cell death in Arabidopsis. Plant J 39:59–69View ArticlePubMedGoogle Scholar
- Wohlgemuth H, Mittelstrass K, Kschieschan S, Bender J, Weigel HJ, Overmyer K, Kangasjärvi J, Sandermann H, Langebartels C (2002) Activation of an oxidative burst is a general feature of sensitive plants exposed to the air pollutant ozone. Plant Cell Environ 25:717–726View ArticleGoogle Scholar
- Zhang T, Liu Y, Yang T, Zhang L, Xu S, Xue L, An L (2006) Diverse signals converge at MAPK cascades in plant. Plant Physiol Biochem 44:274–283View ArticlePubMedGoogle Scholar