201
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Van den Ende W, Valluru R. Sucrose, sucrosyl oligosaccharides, and oxidative stress: scavenging and salvaging? JOURNAL OF EXPERIMENTAL BOTANY 2009; 60:9-18. [PMID: 19036839 DOI: 10.1093/jxb/ern297] [Citation(s) in RCA: 212] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
In nature, no single plant completes its life cycle without encountering environmental stress. When plant cells surpass stress threshold stimuli, chemically reactive oxygen species (ROS) are generated that can cause oxidative damage or act as signals. Plants have developed numerous ROS-scavenging systems to minimize the cytotoxic effects of ROS. The role of sucrosyl oligosaccharides (SOS), including fructans and the raffinose family oligosaccharides (RFOs), is well established during stress physiology. They are believed to act as important membrane protectors in planta. So far a putative role for sucrose and SOS during oxidative stress has largely been neglected, as has the contribution of the vacuolar compartment. Recent studies suggest a link between SOS and oxidative defence and/or scavenging. SOS might be involved in stabilizing membrane-associated peroxidases and NADPH oxidases, and SOS-derived radicals might fulfil an intermediate role in oxido-reduction reactions taking place in the vicinity of membranes. Here, these emerging features are discussed and perspectives for future research are provided.
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Affiliation(s)
- Wim Van den Ende
- Laboratory for Molecular Plant Physiology, KU Leuven, Kasteelpark Arenberg 31, B-3001 Leuven, Belgium.
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202
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Linster CL, Clarke SG. L-Ascorbate biosynthesis in higher plants: the role of VTC2. TRENDS IN PLANT SCIENCE 2008; 13:567-73. [PMID: 18824398 PMCID: PMC2583178 DOI: 10.1016/j.tplants.2008.08.005] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 06/12/2008] [Revised: 07/31/2008] [Accepted: 08/19/2008] [Indexed: 05/17/2023]
Abstract
In the past year, the last missing enzyme of the L-galactose pathway, the linear form of which appears to represent the major biosynthetic route to L-ascorbate (vitamin C) in higher plants, has been identified as a GDP-L-galactose phosphorylase. This enzyme catalyzes the first committed step in the synthesis of that vital antioxidant and enzyme cofactor. Here, we discuss how GDP-L-galactose phosphorylase enzymes, encoded in Arabidopsis by the paralogous VTC2 and VTC5 genes, function in concert with the other enzymes of the L-galactose pathway to provide plants with the appropriate levels of L-ascorbate. We hypothesize that regulation of L-ascorbate biosynthesis might occur at more than one step and warrants further investigation to allow for the manipulation of vitamin C levels in plants.
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Affiliation(s)
- Carole L Linster
- Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California Los Angeles, Los Angeles, CA 90095, USA
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203
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Bustos D, Lascano R, Villasuso AL, Machado E, Senn ME, Córdoba A, Taleisnik E. Reductions in maize root-tip elongation by salt and osmotic stress do not correlate with apoplastic O2*- levels. ANNALS OF BOTANY 2008; 102:551-9. [PMID: 18703541 PMCID: PMC2701787 DOI: 10.1093/aob/mcn141] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2008] [Revised: 05/28/2008] [Accepted: 07/03/2008] [Indexed: 05/08/2023]
Abstract
BACKGROUND AND AIMS Experimental evidence in the literature suggests that O(2)(*-) produced in the elongation zone of roots and leaves by plasma membrane NADPH oxidase activity is required for growth. This study explores whether growth changes along the root tip induced by hyperosmotic treatments in Zea mays are associated with the distribution of apoplastic O(2)(*-). METHODS Stress treatments were imposed using 150 mm NaCl or 300 mM sorbitol. Root elongation rates and the spatial distribution of growth rates in the root tip were measured. Apoplastic O(2)(*-) was determined using nitro blue tetrazolium, and H(2)O(2) was determined using 2', 7'-dichlorofluorescin. KEY RESULTS In non-stressed plants, the distribution of accelerating growth and highest O(2)(*-) levels coincided along the root tip. Salt and osmotic stress of the same intensity had similar inhibitory effects on root elongation, but O(2)(*-) levels increased in sorbitol-treated roots and decreased in NaCl-treated roots. CONCLUSIONS The lack of association between apoplastic O(2)(*-) levels and root growth inhibition under hyper-osmotic stress leads us to hypothesize that under those conditions the role of apoplastic O(2)(*-) may be to participate in signalling processes, that convey information on the nature of the substrate that the growing root is exploring.
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Affiliation(s)
- Dolores Bustos
- IFFIVE-INTA, Camino a 60 Cuadras Km 5 1/2, X5020ICA Córdoba, Argentina
| | - Ramiro Lascano
- IFFIVE-INTA, Camino a 60 Cuadras Km 5 1/2, X5020ICA Córdoba, Argentina
| | - Ana Laura Villasuso
- Química Biológica, FCEFQN, Universidad Nacional de Río Cuarto, X5804BYA Río Cuarto, Córdoba, Argentina
| | - Estela Machado
- Química Biológica, FCEFQN, Universidad Nacional de Río Cuarto, X5804BYA Río Cuarto, Córdoba, Argentina
| | | | - Alicia Córdoba
- IFFIVE-INTA, Camino a 60 Cuadras Km 5 1/2, X5020ICA Córdoba, Argentina
| | - Edith Taleisnik
- IFFIVE-INTA, Camino a 60 Cuadras Km 5 1/2, X5020ICA Córdoba, Argentina
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204
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Hancock RD, Chudek JA, Walker PG, Pont SDA, Viola R. Ascorbic acid conjugates isolated from the phloem of Cucurbitaceae. PHYTOCHEMISTRY 2008; 69:1850-1858. [PMID: 18472116 DOI: 10.1016/j.phytochem.2008.03.022] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2008] [Revised: 03/24/2008] [Accepted: 03/28/2008] [Indexed: 05/26/2023]
Abstract
Analysis of phloem exudates from the fruit of Cucurbitaceae revealed the presence of several compounds with UV-visible absorption spectra identical to that of l-ascorbic acid. In Cucurbita pepo L. (zucchini), the compounds could be isolated from phloem exudates collected from aerial parts of the plant but were not detected in whole tissue homogenates. The compounds isolated from the phloem exudates of C. pepo fruit were eluted from strong anion exchange resin in the same fraction as l-ascorbic acid and were oxidised by ascorbate oxidase (E.C. 1.10.3.3). The major compound purified from C. pepo fruit exudates demonstrated similar redox properties to l-ascorbic acid and synthetic 6-O-glucosyl-l-ascorbic acid (6-GlcAsA) but differed from those of 2-O-glucosyl-l-ascorbic acid (2-GlcAsA) isolated from the fruit of Lycium barbarum L. Parent and fragment ion masses of the compound were consistent with hexosyl-ascorbate in which the hexose moiety was attached to C5 or C6 of AsA. Acid hydrolysis of the major C. pepo compound resulted in the formation of l-ascorbic acid and glucose. The purified compound yielded a proton NMR spectrum that was almost identical to that of synthetic 6-GlcAsA. A series of l-ascorbic acid conjugates have, therefore, been identified in the phloem of Cucurbitaceae and the most abundant conjugate has been identified as 6-GlcAsA. The potential role of such conjugates in the long-distance transport of l-ascorbic acid is discussed.
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Affiliation(s)
- Robert D Hancock
- Scottish Crop Research Institute, Plant Products and Food Quality, Invergowrie, Dundee DD2 5DA, United Kingdom.
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205
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Puckette MC, Tang Y, Mahalingam R. Transcriptomic changes induced by acute ozone in resistant and sensitive Medicago truncatula accessions. BMC PLANT BIOLOGY 2008; 8:46. [PMID: 18433496 PMCID: PMC2395263 DOI: 10.1186/1471-2229-8-46] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2008] [Accepted: 04/23/2008] [Indexed: 05/07/2023]
Abstract
BACKGROUND Tropospheric ozone, the most abundant air pollutant is detrimental to plant and animal health including humans. In sensitive plant species even a few hours of exposure to this potent oxidant (200-300 nL. L-1) leads to severe oxidative stress that manifests as visible cell death. In resistant plants usually no visible symptoms are observed on exposure to similar ozone concentrations. Naturally occurring variability to acute ozone in plants provides a valuable resource for examining molecular basis of the differences in responses to ozone. From our earlier study in Medicago truncatula, we have identified cultivar Jemalong is ozone sensitive and PI 464815 (JE154) is an ozone-resistant accession. Analyses of transcriptome changes in ozone-sensitive and resistant accession will provide important clues for understanding the molecular changes governing the plant responses to ozone. RESULTS Acute ozone treatment (300 nL L-1 for six hours) led to a reactive oxygen species (ROS) burst in sensitive Jemalong six hours post-fumigation. In resistant JE154 increase in ROS levels was much reduced compared to Jemalong. Based on the results of ROS profiling, time points for microarray analysis were one hour into the ozone treatment, end of treatment and onset of an ozone-induced ROS burst at 12 hours. Replicated temporal transcriptome analysis in these two accessions using 17 K oligonucleotide arrays revealed more than 2000 genes were differentially expressed. Significantly enriched gene ontologies (GOs) were identified using the Cluster Enrichment analysis program. A striking finding was the alacrity of JE154 in altering its gene expression patterns in response to ozone, in stark contrast to delayed transcriptional response of Jemalong. GOs involved in signaling, hormonal pathways, antioxidants and secondary metabolism were altered in both accessions. However, the repertoire of genes responding in each of these categories was different between the two accessions. Real-time PCR analysis confirmed the differential expression patterns of a subset of these genes. CONCLUSION This study provided a cogent view of the unique and shared transcriptional responses in an ozone-resistant and sensitive accession that exemplifies the complexity of oxidative signaling in plants. Based on this study, and supporting literature in Arabidopsis we speculate that plants sensitive to acute ozone are impaired in perception of the initial signals generated by the action of this oxidant. This in turn leads to a delayed transcriptional response in the ozone sensitive plants. In resistant plants rapid and sustained activation of several signaling pathways enables the deployment of multiple mechanisms for minimizing the toxicity effect of this reactive molecule.
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Affiliation(s)
- Michael C Puckette
- 246 Noble Research Center, Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK, USA
| | - Yuhong Tang
- The Samuel Roberts Noble Foundation Inc., Plant Biology Division, Ardmore, OK, USA
| | - Ramamurthy Mahalingam
- 246 Noble Research Center, Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK, USA
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206
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Gao Q, Zhang L. Ultraviolet-B-induced oxidative stress and antioxidant defense system responses in ascorbate-deficient vtc1 mutants of Arabidopsis thaliana. JOURNAL OF PLANT PHYSIOLOGY 2008; 165:138-48. [PMID: 17561306 DOI: 10.1016/j.jplph.2007.04.002] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2007] [Revised: 04/16/2007] [Accepted: 04/17/2007] [Indexed: 05/15/2023]
Abstract
Ultraviolet-B (UV-B) radiation has a negative impact on plant cells, and results in the generation of reactive oxygen species (ROS). In order to increase our understanding of the effects of UV-B on antioxidant processes, we investigated the response of an ascorbate-deficient Arabidopsis thaliana mutant vtc1 to short-term increased UV-B exposure. After UV-B supplementation, vtc1 mutants exhibited oxidative damage. Evidence for damage included an increase in H(2)O(2) content and the production of thiobarbituric acid reactive substances (TBARS); a decrease in chlorophyll content and chlorophyll fluorescence parameters were also reported. The vtc1 mutants had higher total glutathione than the wild type (WT) during the first day of UV-B treatment. We found reduced ratio of glutathione/total glutathione and increased ratio of dehydroascorbate/total ascorbate in the vtc1 mutants, compared to the WT plants. In addition, the enzymes responsible for ROS scavenging, including superoxide dismutase, catalase, and ascorbate peroxidase, had insufficient activity in the vtc1 mutants, compared to the WT plants. The same reduced activity in the vtc1 mutants was reported for the enzymes responsible for the regeneration of ascorbate and glutathione (including monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase). These results suggest that the ascorbate-deficient mutant vtc1 is more sensitive to supplementary UV-B treatment than WT plants and ascorbate can be considered an important antioxidant for UV-B radiation.
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Affiliation(s)
- Qian Gao
- Key Laboratory of Arid and Grassland Agroecology, Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou 730000, PR China
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207
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Signaling and Integration of Defense Functions of Tocopherol, Ascorbate and Glutathione. PHOTOPROTECTION, PHOTOINHIBITION, GENE REGULATION, AND ENVIRONMENT 2008. [DOI: 10.1007/1-4020-3579-9_16] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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208
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Errakhi R, Meimoun P, Lehner A, Vidal G, Briand J, Corbineau F, Rona JP, Bouteau F. Anion channel activity is necessary to induce ethylene synthesis and programmed cell death in response to oxalic acid. JOURNAL OF EXPERIMENTAL BOTANY 2008; 59:3121-9. [PMID: 18612171 DOI: 10.1093/jxb/ern166] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Oxalic acid is thought to be a key factor of the early pathogenicity stage in a wide range of necrotrophic fungi. Studies were conducted to determine whether oxalate could induce programmed cell death (PCD) in Arabidopsis thaliana suspension cells and to detail the transduction of the signalling pathway induced by oxalate. Arabidopsis thaliana cells were treated with millimolar concentrations of oxalate. Cell death was quantified and ion flux variations were analysed from electrophysiological measurements. Involvement of the anion channel and ethylene in the signal transduction leading to PCD was determined by using specific inhibitors. Oxalic acid induced a PCD displaying cell shrinkage and fragmentation of DNA into internucleosomal fragments with a requirement for active gene expression and de novo protein synthesis, characteristic hallmarks of PCD. Other responses generally associated with plant cell death, such as anion effluxes leading to plasma membrane depolarization, mitochondrial depolarization, and ethylene synthesis, were also observed following addition of oxalate. The results show that oxalic acid activates an early anionic efflux which is a necessary prerequisite for the synthesis of ethylene and for the PCD in A. thaliana cells.
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Affiliation(s)
- Rafik Errakhi
- LEM (EA 3514), Université Paris Diderot, 2 place Jussieu, 75251 Paris cedex 05, France
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209
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Fotopoulos V, De Tullio MC, Barnes J, Kanellis AK. Altered stomatal dynamics in ascorbate oxidase over-expressing tobacco plants suggest a role for dehydroascorbate signalling. JOURNAL OF EXPERIMENTAL BOTANY 2008; 59:729-37. [PMID: 18349048 DOI: 10.1093/jxb/erm359] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Control of stomatal aperture is of paramount importance for plant adaptation to the surrounding environment. Here, we report on several parameters related to stomatal dynamics and performance in transgenic tobacco plants (Nicotiana tabacum L., cv. Xanthi) over-expressing cucumber ascorbate oxidase (AO), a cell wall-localized enzyme of uncertain biological function that oxidizes ascorbic acid (AA) to monodehydroascorbic acid which dismutates yielding AA and dehydroascorbic acid (DHA). In comparison to WT plants, leaves of AO over-expressing plants exhibited reduced stomatal conductance (due to partial stomatal closure), higher water content, and reduced rates of water loss on detachment. Transgenic plants also exhibited elevated levels of hydrogen peroxide and a decline in hydrogen peroxide-scavenging enzyme activity. Leaf ABA content was also higher in AO over-expressing plants. Treatment of epidermal strips with either 1 mM DHA or 100 microM hydrogen peroxide resulted in rapid stomatal closure in WT plants, but not in AO-over-expressing plants. This suggests that signal perception and/or transduction associated with stomatal closure is altered by AO over-expression. These data support a specific role for cell wall-localized AA in the perception of environmental cues, and suggest that DHA acts as a regulator of stomatal dynamics.
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Affiliation(s)
- Vasileios Fotopoulos
- Group of Biotechnology of Pharmaceutical Plants, Laboratory of Pharmacognocy, Department of Pharmaceutical Sciences, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece
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210
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Colville L, Smirnoff N. Antioxidant status, peroxidase activity, and PR protein transcript levels in ascorbate-deficient Arabidopsis thaliana vtc mutants. JOURNAL OF EXPERIMENTAL BOTANY 2008; 59:3857-68. [PMID: 18849295 DOI: 10.1093/jxb/ern229] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Ascorbate is the most abundant small molecule antioxidant in plants and is proposed to function, along with other members of an antioxidant network, in controlling reactive oxygen species. A biochemical and molecular characterization of four ascorbate-deficient (vtc) Arabidopsis thaliana mutants has been carried out to determine if ascorbate deficiency is compensated by changes in the other major antioxidants. Seedlings grown in vitro were used to minimize stress and longer term developmental differences. Comparison was made with the low glutathione cad2 mutant and vtc2-1 treated with D,L-buthionine-[S,R]-sulphoximine to cause combined ascorbate and glutathione deficiency. The pool sizes and oxidation state of ascorbate and glutathione were not altered by deficiency of the other. alpha-Tocopherol and activities of monodehydroascorbate reductase, dehydroascorbate reductase, glutathione reductase, and catalase were little affected. Ascorbate peroxidase activity was higher in vtc1, vtc2-1, and vtc2-2. Ionically bound cell wall peroxidase activity was increased in vtc1, vtc2-1, and vtc4. Supplementation with ascorbate increased cell wall peroxidase activity. 2,6-Dichlorobenzonitrile, an inhibitor of cellulose synthesis, increased cell wall peroxidase activity in the wild type and vtc1. The transcript level of an endochitinase, PR1, and PR2, but not GST6, was increased in vtc1, vtc2-1, and vtc-2-2. Endochitinase transcript levels increased after ascorbate, paraquat, salicylic acid, and UV-C treatment, PR1 after salicylic acid treatment, and PR2 after paraquat and UV-C treatment. Camalexin was higher in vtc1 and the vtc2 alleles. Induction of PR genes, cell wall peroxidase activity, and camalexin in vtc1, vtc2-1, and vtc2-2 suggests that the mutants are affected in pathogen response signalling pathways.
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Affiliation(s)
- Louise Colville
- School of Biosciences, University of Exeter, Geoffrey Pope Building, Stocker Road, Exeter EX4 4QD, UK
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211
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Zhu J, Alvarez S, Marsh EL, Lenoble ME, Cho IJ, Sivaguru M, Chen S, Nguyen HT, Wu Y, Schachtman DP, Sharp RE. Cell wall proteome in the maize primary root elongation zone. II. Region-specific changes in water soluble and lightly ionically bound proteins under water deficit. PLANT PHYSIOLOGY 2007; 145:1533-48. [PMID: 17951457 PMCID: PMC2151692 DOI: 10.1104/pp.107.107250] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2007] [Accepted: 10/13/2007] [Indexed: 05/17/2023]
Abstract
Previous work on the adaptation of maize (Zea mays) primary roots to water deficit showed that cell elongation is maintained preferentially toward the apex, and that this response involves modification of cell wall extension properties. To gain a comprehensive understanding of how cell wall protein (CWP) composition changes in association with the differential growth responses to water deficit in different regions of the elongation zone, a proteomics approach was used to examine water soluble and loosely ionically bound CWPs. The results revealed major and predominantly region-specific changes in protein profiles between well-watered and water-stressed roots. In total, 152 water deficit-responsive proteins were identified and categorized into five groups based on their potential function in the cell wall: reactive oxygen species (ROS) metabolism, defense and detoxification, hydrolases, carbohydrate metabolism, and other/unknown. The results indicate that stress-induced changes in CWPs involve multiple processes that are likely to regulate the response of cell elongation. In particular, the changes in protein abundance related to ROS metabolism predicted an increase in apoplastic ROS production in the apical region of the elongation zone of water-stressed roots. This was verified by quantification of hydrogen peroxide content in extracted apoplastic fluid and by in situ imaging of apoplastic ROS levels. This response could contribute directly to the enhancement of wall loosening in this region. This large-scale proteomic analysis provides novel insights into the complexity of mechanisms that regulate root growth under water deficit conditions and highlights the spatial differences in CWP composition in the root elongation zone.
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Affiliation(s)
- Jinming Zhu
- Division of Plant Sciences, University of Missouri, Columbia, Missouri 65211, USA
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212
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Dowdle J, Ishikawa T, Gatzek S, Rolinski S, Smirnoff N. Two genes in Arabidopsis thaliana encoding GDP-L-galactose phosphorylase are required for ascorbate biosynthesis and seedling viability. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2007; 52:673-89. [PMID: 17877701 DOI: 10.1111/j.1365-313x.2007.03266.x] [Citation(s) in RCA: 277] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Plants synthesize ascorbate from guanosine diphosphate (GDP)-mannose via L-galactose/L-gulose, although uronic acids have also been proposed as precursors. Genes encoding all the enzymes of the GDP-mannose pathway have previously been identified, with the exception of the step that converts GDP-L-galactose to L-galactose 1-P. We show that a GDP-L-galactose phosphorylase, encoded by the Arabidopsis thaliana VTC2 gene, catalyses this step in the ascorbate biosynthetic pathway. Furthermore, a homologue of VTC2, At5g55120, encodes a second GDP-L-galactose phosphorylase with similar properties to VTC2. Two At5g55120 T-DNA insertion mutants (vtc5-1 and vtc5-2) have 80% of the wild-type ascorbate level. Double mutants were produced by crossing the loss-of-function vtc2-1 mutant with each of the two vtc5 alleles. These show growth arrest immediately upon germination and the cotyledons subsequently bleach. Normal growth was restored by supplementation with ascorbate or L-galactose, indicating that both enzymes are necessary for ascorbate generation. vtc2-1 leaves contain more mannose 6-P than wild-type. We conclude that the GDP-mannose pathway is the only significant source of ascorbate in A. thaliana seedlings, and that ascorbate is essential for seedling growth. A. thaliana leaves accumulate more ascorbate after acclimatization to high light intensity. VTC2 expression and GDP-L-galactose phosphorylase activity rapidly increase on transfer to high light, but the activity of other enzymes in the GDP-mannose pathway is little affected. VTC2 and At5g55120 (VTC5) expression also peak in at the beginning of the light cycle and are controlled by the circadian clock. The GDP-L-galactose phosphorylase step may therefore play an important role in controlling ascorbate biosynthesis.
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Affiliation(s)
- John Dowdle
- School of Biosciences, University of Exeter, Geoffrey Pope Building, Stocker Road, Exeter EX4 4QD, UK
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213
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Marczak Ł, Wojtaszek P, Stobiecki M. Influence of plant secondary metabolites on in vitro oxidation of methyl ferulate with cell wall peroxidases from lupine apoplast. JOURNAL OF PLANT PHYSIOLOGY 2007; 165:239-250. [PMID: 17928101 DOI: 10.1016/j.jplph.2007.06.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2007] [Revised: 06/27/2007] [Accepted: 06/28/2007] [Indexed: 05/25/2023]
Abstract
Ionically bound cell wall peroxidases (POXs) were liberated to intercellular washing fluids (IWFs) and isolated together with other proteins and metabolites present in the apoplast of white lupine (Lupinus albus L. var. Bac) root. After separation of proteins from low molecular weight compounds, activity of peroxidases was monitored in in vitro experiments. Oxidation of methyl ferulate with H2O2 was studied in multi-component mixtures of plant metabolites. Secondary metabolites identified in IWFs or other natural products playing important roles in different physiological processes were applied as modifiers of the dehydrodimerization process during oxidation reactions performed in vitro. These were isoflavones and their conjugates, lupanine representing quinolizidine alkaloids synthesized in lupine, or other natural products such as quercetin, ascorbic, and salicylic acid. The influence of these substances on the oxidation kinetics of methyl ferulate was monitored with liquid chromatography with ultraviolet detection (LC/UV), and identification of compounds was confirmed with the liquid chromatography/mass spectroscopy (LC/MS) system. On the basis of data collected, it was possible to reveal changes in the activities of cell wall POXs. Application of the LC system permitted us to monitor, independently, quantitative changes of two or more reaction products in the mixtures. In multi-component combinations, oxidation yields of methyl ferulate by POXs were modified depending on the actual composition of the reaction mixture. We conclude that various classes of plant secondary metabolites can modify the yield of methyl ferulate oxidation by hydrogen peroxide in the presence of POX, due to interactions with the enzyme's active site (genistein) or radical scavenging properties of metabolites present in the reaction mixture.
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Affiliation(s)
- Łukasz Marczak
- Institute of Bioorganic Chemistry PAS, Noskowskiego 12/14, 61-704 Poznań, Poland
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214
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Rausch T, Gromes R, Liedschulte V, Müller I, Bogs J, Galovic V, Wachter A. Novel insight into the regulation of GSH biosynthesis in higher plants. PLANT BIOLOGY (STUTTGART, GERMANY) 2007; 9:565-72. [PMID: 17853356 DOI: 10.1055/s-2007-965580] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
In higher plants, the redox-active tripeptide glutathione (GSH) fulfills a plethora of functions. These include its pivotal role for maintaining the cellular redox poise and its involvement in detoxification of heavy metals and xenobiotics. Intimately linked to these functions, GSH also acts as a cellular signal, mediating control of enzyme and/or regulatory protein activities, either directly or via glutaredoxins. The redox potential of the GSH/GSSG couple is not only affected by the GSH/GSSG ratio but also by changes in GSH synthesis and/or degradation. As this couple operates as redox buffer in several cellular compartments, the regulation of GSH biosynthesis and transport (both intra- and intercellularly) are fundamental to the maintenance of cellular redox homeostasis during plant development and, even more so, when plants are exposed to biotic or abiotic stress. This review highlights novel aspects of GSH biosynthesis and transport with a focus on the regulation of the GSH1 (= gamma-glutamylcysteine synthetase) enzyme. Interestingly, GSH1 appears to be exclusively confined to the plastids, whereas the second biosynthetic enzyme, GSH2, is predominantly localized in the cytosol. GSH1 expression and enzyme activity are under multiple controls, extending from transcriptional regulation to post-translational redox control. Now that the plant GSH1 protein structure has been solved, the molecular basis of GSH1 function and redox regulation can be addressed. The review concludes with a discussion of the simultaneous changes observed for GSH synthesis, transport, and metabolism during Cd-induced phytochelatin accumulation.
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Affiliation(s)
- T Rausch
- Heidelberg Institute of Plant Sciences, University of Heidelberg, Im Neuenheimer Feld 360, 69120 Heidelberg, Germany.
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215
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Sgherri C, Quartacci MF, Navari-Izzo F. Early production of activated oxygen species in root apoplast of wheat following copper excess. JOURNAL OF PLANT PHYSIOLOGY 2007; 164:1152-60. [PMID: 16920221 DOI: 10.1016/j.jplph.2006.05.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2006] [Accepted: 05/08/2006] [Indexed: 05/11/2023]
Abstract
Wheat seedlings (Triticum durum Desf.) were incubated in a solution containing 100 microM CuSO(4) for increasing time ranging from 1 min to 6h. Copper rapidly accumulated into the roots, and its amount increased significantly until 360 min. During the experiment, copper did not cause any lipid peroxidation and K(+) leakage. Up to 60 min of copper treatment the superoxide (O2(*-)) production in root apoplast decreased concomitantly with increase in superoxide dismutase (SOD) activity. In contrast, after 60 min of incubation, SOD decreased and this facilitated an increase in O2(*-) production. In the presence of the SOD inhibitor diethyldithiocarbamic acid, O2(*-) production was more than two times higher and showed a biphasic increase. Very high SOD activity in the apoplast, due to the presence of three different isozymes, one Mn-SOD and two CuZn-SODs, dismutated the radical giving rise, at least in part, to an increase in hydrogen peroxide. The highest value of H(2)O(2) was detected at 15 min, when peroxidase (POD) activity reached the lowest value. Root apoplast showed the presence of at least five different isoforms of PODs, whose pattern did not change during the entire treatment.
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Affiliation(s)
- Cristina Sgherri
- Dipartimento di Chimica e Biotecnologie Agrarie, Università di Pisa, via del Borghetto 80, 56124, Pisa, Italy
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216
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Foyer CH, Kiddle G, Verrier P. Transcriptional profiling approaches to understanding how plants regulate growth and defence: a case study illustrated by analysis of the role of vitamin C. EXS 2007; 97:55-86. [PMID: 17432263 DOI: 10.1007/978-3-7643-7439-6_3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
In this chapter, basic technical aspects concerning the design of DNA microarray experiments are discussed including sample preparation, hybridisation conditions and statistical significance of the acquired data are detailed. Given that microarrays are perhaps the most used tool in plant systems biology there is much experience in the pitfalls in using them. Herein important considerations are presented for both the experimental biologists and data analyst in order to maximise the utility of these resources. Finally a case study using the analysis of vitamin C deficient plants is presented to illustrate the power of this approach in enhancing comprehension of important and complex biological functions.
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Affiliation(s)
- Christine H Foyer
- Crop Performance and Improvement Division, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK.
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217
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Eltayeb AE, Kawano N, Badawi GH, Kaminaka H, Sanekata T, Shibahara T, Inanaga S, Tanaka K. Overexpression of monodehydroascorbate reductase in transgenic tobacco confers enhanced tolerance to ozone, salt and polyethylene glycol stresses. PLANTA 2007; 225:1255-64. [PMID: 17043889 DOI: 10.1007/s00425-006-0417-7] [Citation(s) in RCA: 206] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2006] [Accepted: 09/20/2006] [Indexed: 05/12/2023]
Abstract
Ascorbate (AsA) is a major antioxidant and free-radical scavenger in plants. Monodehydroascorbate reductase (MDAR; EC 1.6.5.4) is crucial for AsA regeneration and essential for maintaining a reduced pool of AsA. To examine whether an overexpressed level of MDAR could minimize the deleterious effects of environmental stresses, we developed transgenic tobacco plants overexpressing Arabidopsis thaliana MDAR gene (AtMDAR1) in the cytosol. Incorporation of the transgene in the genome of tobacco plants was confirmed by PCR and Southern-blot analysis and its expression was confirmed by Northern- and Western-blot analyses. These transgenic plants exhibited up to 2.1-fold higher MDAR activity and 2.2-fold higher level of reduced AsA compared to non-transformed control plants. The transgenic plants showed enhanced stress tolerance in term of significantly higher net photosynthesis rates under ozone, salt and polyethylene glycol (PEG) stresses and greater PSII effective quantum yield under ozone and salt stresses. Furthermore, these transgenic plants exhibited significantly lower hydrogen peroxide level when tested under salt stress. These results demonstrate that an overexpressed level of MDAR properly confers enhanced tolerance against ozone, salt and PEG stress.
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Affiliation(s)
- Amin Elsadig Eltayeb
- Laboratory of Plant Biotechnology, Faculty of Agriculture, Tottori University, Koyama, Tottori 680-8553, Japan
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218
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Monteiro G, Horta BB, Pimenta DC, Augusto O, Netto LES. Reduction of 1-Cys peroxiredoxins by ascorbate changes the thiol-specific antioxidant paradigm, revealing another function of vitamin C. Proc Natl Acad Sci U S A 2007; 104:4886-91. [PMID: 17360337 PMCID: PMC1829234 DOI: 10.1073/pnas.0700481104] [Citation(s) in RCA: 167] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Peroxiredoxins (Prx) are widely distributed peroxidases that can be divided into 1-Cys and 2-Cys Prx groups based on the number of conserved cysteine residues that participate in their catalytical cycle. Prx have been described to be strictly dependent on thiols, but here, we show that ascorbate (vitamin C) also reduces 1-Cys Prx, but not 2-Cys Prx, from several taxonomic groups. Reduction by ascorbate is partly related to the fact that the oxidized form of 1-Cys Prx is a stable sulfenic acid (Cys-SOH) instead of a disulfide. In addition, a histidine residue in the active site is required. In fact, we engineered a 2-Cys Prx with these two features, and it displayed ascorbate peroxidase activity. These data represent a breakthrough in the thiol-specific antioxidant paradigm. Ascorbate may be the long-sought-after biological reductant of 1-Cys Prx. Because ascorbate is present in high amounts in cells, the ascorbate/protein sulfenic acid pair represents an aspect of redox biochemistry that has yet to be explored in vivo.
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Affiliation(s)
- Gisele Monteiro
- *Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, Rua do Matão 277, CEP 05508-900, São Paulo, Brazil
| | - Bruno B. Horta
- *Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, Rua do Matão 277, CEP 05508-900, São Paulo, Brazil
| | - Daniel Carvalho Pimenta
- Laboratório de Espectrometria de Massa, Centro de Toxinologia Aplicada (CAT/CEPID), Instituto Butantan, CEP 05503-900, São Paulo, Brazil; and
| | - Ohara Augusto
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, CEP 05508-900, São Paulo, Brazil
| | - Luis E. S. Netto
- *Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, Rua do Matão 277, CEP 05508-900, São Paulo, Brazil
- To whom correspondence should be addressed. E-mail:
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219
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Ohkama-Ohtsu N, Radwan S, Peterson A, Zhao P, Badr AF, Xiang C, Oliver DJ. Characterization of the extracellular gamma-glutamyl transpeptidases, GGT1 and GGT2, in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2007; 49:865-77. [PMID: 17316175 DOI: 10.1111/j.1365-313x.2006.03004.x] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
gamma-Glutamyl transpeptidase (GGT) is the only enzyme known that can cleave the gamma-peptide bond between glutamate and cysteine in glutathione, and is therefore a key step in glutathione degradation. There are three functional GGT genes in Arabidopsis, two of which are considered here. GGT1 and GGT2 are apoplastic, associated with the plasma membrane and/or cell wall. RNA blots and analysis of enzyme activity in knockout mutants suggest that GGT1 is expressed most strongly in leaves but is found throughout the plant. A GGT1::GUS fusion construct showed expression only in vascular tissue, specifically the phloem of the mid-rib and minor veins of leaves, roots and flowers. This localization was confirmed in leaves by laser microdissection. GGT2 expression is limited to embryo, endosperm, outer integument, and a small portion of the funiculus in developing siliques. The ggt2 mutants had no detectable phenotype, while the ggt1 knockouts were smaller and flowered sooner than wild-type. In ggt1 plants, the cotyledons and older leaves yellowed early, and GSSG, the oxidized form of glutathione, accumulated in the apoplastic space. These observations suggest that GGT1 is important in preventing oxidative stress by metabolizing extracellular GSSG, while GGT2 might be important in transporting glutathione into developing seeds.
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Affiliation(s)
- Naoko Ohkama-Ohtsu
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011, USA
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220
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Sanmartin M, Pateraki I, Chatzopoulou F, Kanellis AK. Differential expression of the ascorbate oxidase multigene family during fruit development and in response to stress. PLANTA 2007; 225:873-85. [PMID: 17021803 DOI: 10.1007/s00425-006-0399-5] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2006] [Accepted: 08/29/2006] [Indexed: 05/12/2023]
Abstract
Ascorbate oxidase (AO, EC 1.10.3.3) is a member of the multicopper oxidases family. It catalyzes the oxidation of ascorbic acid (AA) to dehydroascorbic acid (DHA) via monodehydroascorbate (MDHA), with the concomitant reduction of molecular oxygen to water. In melon (Cucumis melo), ascorbate oxidase is encoded by a multigene family comprising at least four genes. Here, we present the detailed characterization of two melon AO genes, CmAO1 and CmAO4. Gene-specific expression studies of the AO gene family in melon revealed that only CmAO1 and CmAO4 are transcriptionally active and differentially regulated dependent on tissue, developmental stage and external stimuli. Transcripts of the CmAO1 gene are present in floral and fruit tissues, whereas CmAO4 mRNA preferentially accumulates in vegetative tissues. CmAO genes were not detected in melon seeds, but CmAO4 expression is activated upon germination. CmAO4 mRNA steady-state levels are also regulated in response to wounding and heat stress, by hormones (abscisic acid, salicylic acid and jasmonates), AA and copper. These findings suggest that AO gene expression is transcriptionally regulated during fruit development and in response to hormonal cues associated with the control of cell growth and the stress response.
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Affiliation(s)
- Maite Sanmartin
- Group of Biotechnology of Pharmaceutical Plants, Laboratory of Pharmacognocy, Department of Pharmaceutical Sciences, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece
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221
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Puckette MC, Weng H, Mahalingam R. Physiological and biochemical responses to acute ozone-induced oxidative stress in Medicago truncatula. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2007; 45:70-9. [PMID: 17270456 DOI: 10.1016/j.plaphy.2006.12.004] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2006] [Accepted: 12/18/2006] [Indexed: 05/03/2023]
Abstract
Oxidative signaling mediated by reactive oxygen species (ROS) is a central component of biotic and abiotic stresses in plants. Acute ozone (O(3)) fumigation is a useful non-invasive treatment for eliciting endogenous ROS in planta. In this study, 38 different accessions of the model legume, Medicago truncatula, from various geographical regions were fumigated with 300 nmol mol(-1) of O(3) for a period of six hours. Phenotypic symptoms were evaluated 24 and 48 h after the end of treatment. A majority of the accessions showed distinct visible damage. Eight accessions showing varying sensitivities to ozone were subjected to biochemical analysis to evaluate correlations between ozone damage and levels of ROS, antioxidants, and lipid peroxidation. Two-way analysis of variance indicated highly significant interactions between O(3) damage and levels of ROS, ascorbate, glutathione and lipid peroxidation. There were significant differences among the accessions for these traits before and after the end of O(3) fumigation, as indicated by equal variance Student's t-test. This study suggests that multiple physiological and biochemical mechanisms may govern O(3) tolerance or sensitivity. Surveying a large collection of germplasm led to identification of multiple resistant and sensitive lines for investigating molecular basis of O(3) phytotoxicity. The most resistant JE154 accession also showed enhanced tolerance to chronic O(3) and dehydration stress, suggesting germplasm with increased tolerance to acute O(3) can be a useful resource for improving resistance to multiple abiotic stressors.
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Affiliation(s)
- Michael C Puckette
- Department of Biochemistry and Molecular Biology, Oklahoma State University, 246 Noble Research Center, Stillwater, OK 74078, USA
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222
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Laloi C, Stachowiak M, Pers-Kamczyc E, Warzych E, Murgia I, Apel K. Cross-talk between singlet oxygen- and hydrogen peroxide-dependent signaling of stress responses in Arabidopsis thaliana. Proc Natl Acad Sci U S A 2006; 104:672-7. [PMID: 17197417 PMCID: PMC1766442 DOI: 10.1073/pnas.0609063103] [Citation(s) in RCA: 232] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Upon a dark-to-light shift, the conditional fluorescent (flu) mutant of Arabidopsis releases singlet oxygen (1O2) within the plastid compartment. Distinct sets of nuclear genes are activated that are different from those induced by superoxide (O2*-)) and/or hydrogen peroxide (H2O2), suggesting that different types of reactive oxygen species activate distinct signaling pathways. It is not known whether the pathways operate separately or interact with each other. We have addressed this problem by modulating noninvasively the level of H2O2 in plastids by means of a transgenic line that overexpresses the thylakoid-bound ascorbate peroxidase (tAPX). The overexpression of the H2O2-specific scavenger reduced strongly the activation of nuclear genes in plants treated with the herbicide paraquat that in the light leads to the enhanced generation of O2*- and H2O2. In the flu mutant overexpressing tAPX, the intensity of 1O2-mediated cell death and growth inhibition was increased when compared with the flu parental line. Also, the expression of most of the nuclear genes that were rapidly activated after the release of 1O2 was significantly higher in flu plants overexpressing tAPX, whereas in wild-type plants, overexpression of tAPX did not lead to visible stress responses and had only a very minor impact on nuclear gene expression. The results suggest that H2O2 antagonizes the 1O2-mediated signaling of stress responses as seen in the flu mutant. This cross-talk between H2O2- and 1O2-dependent signaling pathways might contribute to the overall stability and robustness of wild-type plants exposed to adverse environmental stress conditions.
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Affiliation(s)
- Christophe Laloi
- Institute of Plant Science, Eidgenössische Technische Hochschule Zurich, 8092 Zurich, Switzerland.
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223
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Navrot N, Collin V, Gualberto J, Gelhaye E, Hirasawa M, Rey P, Knaff DB, Issakidis E, Jacquot JP, Rouhier N. Plant glutathione peroxidases are functional peroxiredoxins distributed in several subcellular compartments and regulated during biotic and abiotic stresses. PLANT PHYSIOLOGY 2006; 142:1364-79. [PMID: 17071643 PMCID: PMC1676047 DOI: 10.1104/pp.106.089458] [Citation(s) in RCA: 237] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
We provide here an exhaustive overview of the glutathione (GSH) peroxidase (Gpx) family of poplar (Populus trichocarpa). Although these proteins were initially defined as GSH dependent, in fact they use only reduced thioredoxin (Trx) for their regeneration and do not react with GSH or glutaredoxin, constituting a fifth class of peroxiredoxins. The two chloroplastic Gpxs display a marked selectivity toward their electron donors, being exclusively specific for Trxs of the y type for their reduction. In contrast, poplar Gpxs are much less specific with regard to their electron-accepting substrates, reducing hydrogen peroxide and more complex hydroperoxides equally well. Site-directed mutagenesis indicates that the catalytic mechanism and the Trx-mediated recycling process involve only two (cysteine [Cys]-107 and Cys-155) of the three conserved Cys, which form a disulfide bridge with an oxidation-redox midpoint potential of -295 mV. The reduction/formation of this disulfide is detected both by a shift on sodium dodecyl sulfate-polyacrylamide gel electrophoresis or by measuring the intrinsic tryptophan fluorescence of the protein. The six genes identified coding for Gpxs are expressed in various poplar organs, and two of them are localized in the chloroplast, with one colocalizing in mitochondria, suggesting a broad distribution of Gpxs in plant cells. The abundance of some Gpxs is modified in plants subjected to environmental constraints, generally increasing during fungal infection, water deficit, and metal stress, and decreasing during photooxidative stress, showing that Gpx proteins are involved in the response to both biotic and abiotic stress conditions.
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Affiliation(s)
- Nicolas Navrot
- Unité Mixte de Recherche Institut National de la Recherche Agronomique-Université Henri Poincaré 1136, Université Henri Poincaré, 54506 Vandoeuvre cedex, France
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224
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Yannarelli GG, Noriega GO, Batlle A, Tomaro ML. Heme oxygenase up-regulation in ultraviolet-B irradiated soybean plants involves reactive oxygen species. PLANTA 2006; 224:1154-62. [PMID: 16703357 DOI: 10.1007/s00425-006-0297-x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2006] [Accepted: 04/17/2006] [Indexed: 05/04/2023]
Abstract
Ultraviolet-B (UV-B) radiation has a negative impact on plant cells, and leads to the generation of reactive oxygen species (ROS). Heme oxygenase (HO, EC 1.14.99.3) plays a protective role against oxidative stress in mammals, but little is known about this issue in plants. Here, we report for the first time the response of HO in leaves of soybean (Glycine max L.) plants subjected to UV-B radiation. Under 7.5 and 15 kJ m(-2 )UV-B doses, HO, catalase (CAT, EC 1.11.1.6) and ascorbate peroxidase (APX, EC 1.11.1.11) activities were increased and the production of thiobarbituric acid reactive substances (TBARS) regain control values after 4 h of plant recuperation. Treatment with 30 kJ m(-2) UV-B provoked a decrease in these antioxidant enzyme activities. Immunoblot analysis showed a 4.3 and 3.7-fold increase in HO-1 protein expression after irradiation with 7.5 and 15 kJ m(-2), respectively. HO-1 transcript levels were enhanced (up to 77%) at these doses, as assessed by semi-quantitative RT-PCR. These data demonstrated that increased HO activity was associated with augmented protein expression and transcript levels. Plants pre-treated with the antioxidant ascorbic acid did not show the UV-B-induced up-regulation of HO-1 mRNA, but hydrogen peroxide treatment could mimic this reaction. Our results indicate that HO is up-regulated in a dose-depending manner as a mechanism of cell protection against oxidative damage and that such response occurred as a consequence of HO-1 mRNA enhancement involving ROS.
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Affiliation(s)
- Gustavo G Yannarelli
- Departamento de Química Biológica, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, Buenos Aires, 1113, Argentina.
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225
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Stevens R, Buret M, Garchery C, Carretero Y, Causse M. Technique for rapid, small-scale analysis of vitamin C levels in fruit and application to a tomato mutant collection. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2006; 54:6159-65. [PMID: 16910702 DOI: 10.1021/jf061241e] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
We present a technique for easy, rapid analysis of both total and reduced forms of vitamin C in fruits using microplates and a plate reader. This technique has been compared with a spectrofluorometric technique classically used for assaying vitamin C in fresh tomato. We have applied these methods to a population of 118 tomato mutant lines and controls in search of variability for this trait. Six lines, identified as having high vitamin C levels, and four lines having low vitamin C levels have been chosen for further study. The vitamin C levels have been compared with sugar concentration, dry matter content, fruit weight, titratable acidity, and firmness. The correlations that often exist in tomato varieties between sugar and vitamin C content (positive correlation) or fruit weight and vitamin C content (negative correlation) can be uncoupled in the lines selected for further analysis.
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Affiliation(s)
- Rebecca Stevens
- Unité de Génétique et Amélioration des Fruits et Légumes, UR1052, INRA, Domaine St. Maurice BP94, 84143 Montfavet, France.
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226
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Hoegger PJ, Kilaru S, James TY, Thacker JR, Kües U. Phylogenetic comparison and classification of laccase and related multicopper oxidase protein sequences. FEBS J 2006; 273:2308-26. [PMID: 16650005 DOI: 10.1111/j.1742-4658.2006.05247.x] [Citation(s) in RCA: 293] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A phylogenetic analysis of more than 350 multicopper oxidases (MCOs) from fungi, insects, plants, and bacteria provided the basis for a refined classification of this enzyme family into laccases sensu stricto (basidiomycetous and ascomycetous), insect laccases, fungal pigment MCOs, fungal ferroxidases, ascorbate oxidases, plant laccase-like MCOs, and bilirubin oxidases. Within the largest group of enzymes, formed by the 125 basidiomycetous laccases, the gene phylogeny does not strictly follow the species phylogeny. The enzymes seem to group at least partially according to the lifestyle of the corresponding species. Analyses of the completely sequenced fungal genomes showed that the composition of MCOs in the different species can be very variable. Some species seem to encode only ferroxidases, whereas others have proteins which are distributed over up to four different functional clusters in the phylogenetic tree.
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Affiliation(s)
- Patrik J Hoegger
- Georg-August-University Göttingen, Institute of Forest Botany, Göttingen, Germany.
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227
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Pignocchi C, Kiddle G, Hernández I, Foster SJ, Asensi A, Taybi T, Barnes J, Foyer CH. Ascorbate oxidase-dependent changes in the redox state of the apoplast modulate gene transcript accumulation leading to modified hormone signaling and orchestration of defense processes in tobacco. PLANT PHYSIOLOGY 2006; 141:423-35. [PMID: 16603663 PMCID: PMC1475448 DOI: 10.1104/pp.106.078469] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2006] [Revised: 03/24/2006] [Accepted: 03/27/2006] [Indexed: 05/08/2023]
Abstract
The role of the redox state of the apoplast in hormone responses, signaling cascades, and gene expression was studied in transgenic tobacco (Nicotiana tabacum) plants with modified cell wall-localized ascorbate oxidase (AO). High AO activity specifically decreased the ascorbic acid (AA) content of the apoplast and altered plant growth responses triggered by hormones. Auxin stimulated shoot growth only when the apoplastic AA pool was reduced in wild-type or AO antisense lines. Oxidation of apoplastic AA in AO sense lines was associated with loss of the auxin response, higher mitogen-activated protein kinase activities, and susceptibility to a virulent strain of the pathogen Pseudomonas syringae. The total leaf glutathione pool, the ratio of reduced glutathione to glutathione disulfide, and glutathione reductase activities were similar in the leaves of all lines. However, AO sense leaves exhibited significantly lower dehydroascorbate reductase and ascorbate peroxidase activities than wild-type and antisense leaves. The abundance of mRNAs encoding antioxidant enzymes was similar in all lines. However, the day/night rhythms in the abundance of transcripts encoding the three catalase isoforms were changed in response to the AA content of the apoplast. Other transcripts influenced by AO included photorespiratory genes and a plasma membrane Ca(2+) channel-associated gene. We conclude that the redox state of the apoplast modulates plant growth and defense responses by regulating signal transduction cascades and gene expression patterns. Hence, AO activity, which modulates the redox state of the apoplastic AA pool, strongly influences the responses of plant cells to external and internal stimuli.
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Affiliation(s)
- Cristina Pignocchi
- Crop Performance and Improvement Division , Rothamsted Research, Harpenden, Herts AL5 2JQ, United Kingdom
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228
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Noctor G. Metabolic signalling in defence and stress: the central roles of soluble redox couples. PLANT, CELL & ENVIRONMENT 2006; 29:409-25. [PMID: 17080595 DOI: 10.1111/j.1365-3040.2005.01476.x] [Citation(s) in RCA: 252] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Plant growth and development are driven by electron transfer reactions. Modifications of redox components are both monitored and induced by cells, and are integral to responses to environmental change. Key redox compounds in the soluble phase of the cell are NAD, NADP, glutathione and ascorbate--all of which interact strongly with reactive oxygen. This review takes an integrated view of the NAD(P)-glutathione-ascorbate network. These compounds are considered not as one-dimensional 'reductants' or 'antioxidants' but as redox couples that can act together to condition cellular redox tone or that can act independently to transmit specific information that tunes signalling pathways. Emphasis is placed on recent developments highlighting the complexity of redox-dependent defence reactions, and the importance of interactions between the reduction state of soluble redox couples and their concentration in mediating dynamic signalling in response to stress. Signalling roles are assessed within the context of interactions with reactive oxygen, phytohormones and calcium, and the biochemical reactions through which redox couples could be sensed are discussed.
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Affiliation(s)
- Graham Noctor
- Institut de Biotechnologie des Plantes, UMR CNRS 8618, Université de Paris XI, 91405 Orsay cedex, France.
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229
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Holmgren A, Brunow G, Henriksson G, Zhang L, Ralph J. Non-enzymatic reduction of quinone methides during oxidative coupling of monolignols: implications for the origin of benzyl structures in lignins. Org Biomol Chem 2006; 4:3456-61. [PMID: 17036140 DOI: 10.1039/b606369a] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Lignin is believed to be synthesized by oxidative coupling of 4-hydroxyphenylpropanoids. In native lignin there are some types of reduced structures that cannot be explained solely by oxidative coupling. In the present work we showed via biomimetic model experiments that nicotinamide adenine dinucleotide (NADH), in an uncatalyzed process, reduced a beta-aryl ether quinone methide to its benzyl derivative. A number of other biologically significant reductants, including the enzyme cellobiose dehydrogenase, failed to produce the reduced structures. Synthetic dehydrogenation polymers of coniferyl alcohol synthesized (under oxidative conditions) in the presence of the reductant NADH produced the same kind of reduced structures as in the model experiment, demonstrating that oxidative and reductive processes can occur in the same environment, and that reduction of the in situ-generated quinone methides was sufficiently competitive with water addition. In situ reduction of beta-beta-quinone methides was not achieved in this study. The origin of racemic benzyl structures in lignins therefore remains unknown, but the potential for simple chemical reduction is demonstrated here.
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Affiliation(s)
- Anders Holmgren
- Department of Fiber and Polymer Technology, School of Chemical Sciences, Royal Institute of Technology, KTH, 100 44 Stockholm, Sweden
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230
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De Cnodder T, Vissenberg K, Van Der Straeten D, Verbelen JP. Regulation of cell length in the Arabidopsis thaliana root by the ethylene precursor 1-aminocyclopropane- 1-carboxylic acid: a matter of apoplastic reactions. THE NEW PHYTOLOGIST 2005; 168:541-50. [PMID: 16313637 DOI: 10.1111/j.1469-8137.2005.01540.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Treatment of the Arabidopsis thaliana root with the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) immediately imposes a reduced maximal cell length beyond which further elongation is blocked. Here, we investigated possible apoplastic reactions involved in the inhibition of cell elongation. Five-day-old Arabidopsis seedlings were transferred to a growth medium supplemented with ACC and the effect on root cell length was recorded after 3 h of treatment. Altered characteristics in the apoplast of the nonelongating cells in the ACC-treated root, such as 'reactive oxygen species' (ROS) production and callose deposition, were detected using specific fluorochromes. The presence of functional hydroxyproline-rich glycoproteins (HRGPs) and the crosslinking of these cell-wall proteins are essential in limiting cell elongation. The ROS that drive the oxidative crosslinking of HRGPs, accumulate in the apoplast of cells in the zone where cell elongation stops. In the same cells, callose is deposited in the cell wall. The final cell length in the Arabidopsis root treated for a short period with ACC is determined in the zone of fast elongation. Both HRGPs crosslinking by ROS and callose deposition in the cell wall of this zone are suggested as causes for the reduced cell elongation.
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Affiliation(s)
- T De Cnodder
- Department of Biology, University of Antwerp, Campus Drie Eiken, Universiteitsplein 1, B-2610 Wilrijk, Belgium
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231
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Huang C, He W, Guo J, Chang X, Su P, Zhang L. Increased sensitivity to salt stress in an ascorbate-deficient Arabidopsis mutant. JOURNAL OF EXPERIMENTAL BOTANY 2005; 56:3041-9. [PMID: 16263910 DOI: 10.1093/jxb/eri301] [Citation(s) in RCA: 205] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The Arabidopsis thaliana ascorbate-deficient vtc-1 mutant has only 30% ascorbate contents of the wild type (WT). This ascorbate-deficient mutant was used here to study the physiological roles of ascorbate under salt stress in vivo. Salt stress resulted in a more significant decrease in CO2 assimilatory capacity in the vtc-1 mutant than in the WT. Photosystem II function in the Arabidopsis vtc-1 mutant also showed an increased sensitivity to salt stress. Oxidative stress, indicated by the hydrogen peroxide content, increased more dramatically in the vtc-1 mutant than in the WT under salt stress. To clarify the reason for the increased oxidative stress in the vtc-1 mutant, the contents of small antioxidant compounds and the activities of several antioxidant enzymes in the ascorbate-glutathione cycle were measured. Despite an elevated glutathione pool in the vtc-1 mutant, the ascorbate contents and the reduced form of ascorbate decreased very rapidly under salt stress. These results showed that the activities of MDAR and DHAR were lower in the vtc-1 mutant than in the WT under salt stress. Thus, low intrinsic ascorbate and an impaired ascorbate-glutathione cycle in the vtc-1 mutant under salt stress probably induced a dramatic decrease in the reduced form of ascorbate, which resulted in both enhanced ROS contents and decreased NPQ in the vtc-1 mutant.
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Affiliation(s)
- Chenghong Huang
- Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, 730000, China
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232
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Sasaki-Sekimoto Y, Taki N, Obayashi T, Aono M, Matsumoto F, Sakurai N, Suzuki H, Hirai MY, Noji M, Saito K, Masuda T, Takamiya KI, Shibata D, Ohta H. Coordinated activation of metabolic pathways for antioxidants and defence compounds by jasmonates and their roles in stress tolerance in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2005; 44:653-68. [PMID: 16262714 DOI: 10.1111/j.1365-313x.2005.02560.x] [Citation(s) in RCA: 193] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Jasmonic acid (JA) and methyl jasmonate (MeJA), collectively termed jasmonates, are ubiquitous plant signalling compounds. Several types of stress conditions, such as wounding and pathogen infection, cause endogenous JA accumulation and the expression of jasmonate-responsive genes. Although jasmonates are important signalling components for the stress response in plants, the mechanism by which jasmonate signalling contributes to stress tolerance has not been clearly defined. A comprehensive analysis of jasmonate-regulated metabolic pathways in Arabidopsis was performed using cDNA macroarrays containing 13516 expressed sequence tags (ESTs) covering 8384 loci. The results showed that jasmonates activate the coordinated gene expression of factors involved in nine metabolic pathways belonging to two functionally related groups: (i) ascorbate and glutathione metabolic pathways, which are important in defence responses to oxidative stress, and (ii) biosynthesis of indole glucosinolate, which is a defence compound occurring in the Brassicaceae family. We confirmed that JA induces the accumulation of ascorbate, glutathione and cysteine and increases the activity of dehydroascorbate reductase, an enzyme in the ascorbate recycling pathway. These antioxidant metabolic pathways are known to be activated under oxidative stress conditions. Ozone (O3) exposure, a representative oxidative stress, is known to cause activation of antioxidant metabolism. We showed that O3 exposure caused the induction of several genes involved in antioxidant metabolism in the wild type. However, in jasmonate-deficient Arabidopsis 12-oxophytodienoate reductase 3 (opr3) mutants, the induction of antioxidant genes was abolished. Compared with the wild type, opr3 mutants were more sensitive to O3 exposure. These results suggest that the coordinated activation of the metabolic pathways mediated by jasmonates provides resistance to environmental stresses.
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Affiliation(s)
- Yuko Sasaki-Sekimoto
- Tokyo Institute of Technology, Graduate School of Bioscience and Biotechnology, Yokohama, Kanagawa, 226-8501, Japan.
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233
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Abstract
The establishment of the Angiosperm root apical meristem is dependent on the specification of a stem cell niche and the subsequent development of the quiescent center at the presumptive root pole. Distribution of auxin and the establishment of auxin maxima are early formative steps in niche specification that depend on the expression and distribution of auxin carriers. Auxin specifies stem cell niche formation by directly and indirectly affecting gene activities. Part of the indirect regulation by auxin may involve changes in redox, favoring local, oxidized microenvironments. Formation of a QC is required for root meristem development and elaboration. Many signals likely pass between the QC and the adjacent root meristem tissues. Disappearance of the QC is associated with roots becoming determinate. Given the many auxin feedback loops, we hypothesize that roots evolved as part of an auxin homeostasis mechanism.
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Affiliation(s)
- Keni Jiang
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720, USA.
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234
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Waller F, Achatz B, Baltruschat H, Fodor J, Becker K, Fischer M, Heier T, Hückelhoven R, Neumann C, von Wettstein D, Franken P, Kogel KH. The endophytic fungus Piriformospora indica reprograms barley to salt-stress tolerance, disease resistance, and higher yield. Proc Natl Acad Sci U S A 2005; 102:13386-91. [PMID: 16174735 PMCID: PMC1224632 DOI: 10.1073/pnas.0504423102] [Citation(s) in RCA: 589] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Disease resistance strategies are powerful approaches to sustainable agriculture because they reduce chemical input into the environment. Recently, Piriformospora indica, a plant-root-colonizing basidiomycete fungus, has been discovered in the Indian Thar desert and was shown to provide strong growth-promoting activity during its symbiosis with a broad spectrum of plants. Here, we report on the potential of P. indica to induce resistance to fungal diseases and tolerance to salt stress in the monocotyledonous plant barley. The beneficial effect on the defense status is detected in distal leaves, demonstrating a systemic induction of resistance by a root-endophytic fungus. The systemically altered "defense readiness" is associated with an elevated antioxidative capacity due to an activation of the glutathione-ascorbate cycle and results in an overall increase in grain yield. Because P. indica can be easily propagated in the absence of a host plant, we conclude that the fungus could be exploited to increase disease resistance and yield in crop plants.
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Affiliation(s)
- Frank Waller
- Institute of Phytopathology and Applied Zoology, University of Giessen, D-35392 Giessen, Germany
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235
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Nanasato Y, Akashi K, Yokota A. Co-expression of cytochrome b561 and ascorbate oxidase in leaves of wild watermelon under drought and high light conditions. PLANT & CELL PHYSIOLOGY 2005; 46:1515-24. [PMID: 16020428 DOI: 10.1093/pcp/pci164] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Despite carrying out C3 photosynthesis, wild watermelon (Citrullus lanatus sp.) exhibits exceedingly good tolerance to severe drought at high light intensities. However, the mechanism(s) by which this plant protects itself from photodamage has yet to be elucidated. In this study, we characterized wild watermelon cytochrome b561 (cyt b561), which potentially mediates regeneration of apoplastic ascorbate by transferring electrons from cytosolic ascorbate across the plasma membrane. Two cDNA species for wild watermelon cyt b561, designated CLb561A and CLb561B, were isolated. Levels of both CLb561A mRNA and protein were significantly elevated in the leaves during drought at a light intensity of 700 micromol photons m(-2) s(-1). The transcript of CLb561B was detected to a much lesser extent, but no CLb561B protein was produced under any condition used in this study. A transient expression assay with the CLb561A::green fluorescent protein fusion construct showed clear fluorescence on the plasma membrane of onion epidermal cells. The CLb561A protein was enriched in the plasma membrane fraction in leaves of transgenic tobacco expressing CLb561A. Moreover, the high activity of apoplastic ascorbate oxidase (AO), which was able to dispose of cyt b561-transferred reducing equivalents, increased in leaves of wild watermelon grown at high light intensity, but not lower light intensities. Taken together, these observations suggest the occurrence of a novel pathway for excess light energy dissipation in wild watermelon leaves, where excessive energy absorbed by chloroplasts can be transported to and dissipated safely in the apoplasts through the cooperative action of cyt b561 and AO.
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Affiliation(s)
- Yoshihiko Nanasato
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara, 630-0192 Japan
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236
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Gratão PL, Polle A, Lea PJ, Azevedo RA. Making the life of heavy metal-stressed plants a little easier. FUNCTIONAL PLANT BIOLOGY : FPB 2005; 32:481-494. [PMID: 32689149 DOI: 10.1071/fp05016] [Citation(s) in RCA: 457] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2005] [Accepted: 04/28/2005] [Indexed: 05/04/2023]
Abstract
The contamination of soils and water with metals has created a major environmental problem, leading to considerable losses in plant productivity and hazardous health effects. Exposure to toxic metals can intensify the production of reactive oxygen species (ROS), which are continuously produced in both unstressed and stressed plants cells. Some of the ROS species are highly toxic and must be detoxified by cellular stress responses, if the plant is to survive and grow. The aim of this review is to assess the mode of action and role of antioxidants in protecting plants from stress caused by the presence of heavy metals in the environment.
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Affiliation(s)
- Priscila L Gratão
- Departamento de Genética, Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, Piracicaba CEP 13418-900, SP, Brazil
| | - Andrea Polle
- Forstbotanisches Institut, Universität Göttingen, Büsgenweg 2, 37077 Göttingen, Germany
| | - Peter J Lea
- Department of Biological Sciences, University of Lancaster, Lancaster LA1 4YQ, United Kingdom
| | - Ricardo A Azevedo
- Departamento de Genética, Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, Piracicaba CEP 13418-900, SP, Brazil
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237
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Shi Q, Bao Z, Zhu Z, He Y, Qian Q, Yu J. Silicon-mediated alleviation of Mn toxicity in Cucumis sativus in relation to activities of superoxide dismutase and ascorbate peroxidase. PHYTOCHEMISTRY 2005; 66:1551-9. [PMID: 15963540 DOI: 10.1016/j.phytochem.2005.05.006] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2004] [Revised: 03/24/2005] [Indexed: 05/03/2023]
Abstract
The effects of exogenous silicon (Si) on plant growth, activities of superoxide dismutase (SOD), guaiacol peroxidase (GPX), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), glutathione reductase (GR) and catalase, and concentrations of ascorbate and glutathione were investigated in cucumber (Cucumis sativus L.) plants treated with excess manganese (Mn) (600 microM). Compared with the treatment of normal Mn (10 microM), excess Mn significantly increased H2O2 concentration and lipid peroxidation indicated by accumulation of thiobarbituric acid reactive substances. The leaves showed apparent symptoms of Mn toxicity and the plant growth was significantly inhibited by excess Mn. The addition of Si significantly decreased lipid peroxidation caused by excess Mn, inhibited the appearance of Mn toxicity symptoms, and improved plant growth. This alleviation of Mn toxicity by Si was related to a significant increase in the activities of SOD, APX, DHAR and GR and the concentrations of ascorbate and glutathione.
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Affiliation(s)
- Qinghua Shi
- Department of Horticulture, Zhejiang University, Hangzhou 310029, PR China
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238
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Yamamoto A, Bhuiyan MNH, Waditee R, Tanaka Y, Esaka M, Oba K, Jagendorf AT, Takabe T. Suppressed expression of the apoplastic ascorbate oxidase gene increases salt tolerance in tobacco and Arabidopsis plants. JOURNAL OF EXPERIMENTAL BOTANY 2005; 56:1785-96. [PMID: 15883131 DOI: 10.1093/jxb/eri167] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Transgenic tobacco plants expressing the ascorbate oxidase (AAO) gene in sense and antisense orientations, and an Arabidopsis mutant in which the T-DNA was inserted into a putative AAO gene, were used to examine the potential roles of AAO for salt-stress tolerance in plants. AAO activities in the transgenic tobacco plants expressing the gene in sense and antisense orientations were, respectively, about 16-fold and 0.2-fold of those in the wild type. Under normal growth conditions, no significant differences in phenotypes were observed, except for a delay in flowering time in the antisense plants. However, at high salinity, the percentage germination, photosynthetic activity, and seed yields were higher in antisense plants, with progressively lower levels in the wild type and the sense plants. The redox state of apoplastic ascorbate in sense plants was very low even under normal growth conditions. Upon salt stress, the redox state of symplastic and apoplastic ascorbate decreased among the three types of plants, but was lowest in the sense plants. The hydrogen peroxide contents in the symplastic and apoplastic spaces were higher in sense plants, progressively lower in the wild type, followed by the antisense plants. The Arabidopsis T-DNA inserted mutant exhibited very low ascorbate oxidase activity, and its phenotype was similar to that of antisense tobacco plants. These results suggest that the suppressed expression of apoplastic AAO under salt-stress conditions leads to a relatively low level of hydrogen peroxide accumulation and a high redox state of symplastic and apoplastic ascorbate which, in turn, permits a higher seed yield.
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Affiliation(s)
- Atsuko Yamamoto
- Graduate School of Environmental and Human Sciences, Meijo University, Nagoya, 468-8502, Japan
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239
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Ben Rejeb I, Lenne C, Leblanc N, Julien JL, Ammar S, Bouzid S, Ayadi A. Iron-superoxide dismutase and monodehydroascorbate reductase transcripts accumulate in response to internode rubbing in tomato. C R Biol 2005; 327:679-86. [PMID: 15344817 DOI: 10.1016/j.crvi.2004.06.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A cDNA encoding an iron-superoxide dismutase (Fe-SOD) was isolated by RACE-PCR from a Lycopersicon esculentum cDNA library. The Fe-SOD cDNA consists of a 746-bp open reading frame and is predicted to encode a protein of 249 amino acids with a calculated molecular mass of 27.9 kDa. The deduced amino acid sequence was very similar to other plant Fe-SODs and a potential chloroplastic targeting was found. To study the induction of oxidative burst in response to mechanical stimulation, the accumulation of Fe-SOD and monodehydroascorbate reductase (MDHAR) mRNAs was analysed in response to young growing internode rubbing in tomato plants. Northern analyses show that Fe-SOD mRNA and MDHAR mRNA accumulated in tomato internodes 10 min after the mechanical stimulation. These results suggest that reactive oxygen species are early involved in the response of a plant to a mechanical stimulation, such as rubbing. The nucleotide sequence data reported in this paper will appear in the NCBI Nucleotide Sequence Databases under the accession number AY262025.
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Affiliation(s)
- Ichrak Ben Rejeb
- Laboratoire de biologie et physiologie végétales, département de biologie, faculté des sciences de Tunis, campus universitaire, 1060 Tunis, Tunisia.
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240
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Tokunaga T, Miyahara K, Tabata K, Esaka M. Generation and properties of ascorbic acid-overproducing transgenic tobacco cells expressing sense RNA for l-galactono-1,4-lactone dehydrogenase. PLANTA 2005; 220:854-63. [PMID: 15549373 DOI: 10.1007/s00425-004-1406-3] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2004] [Accepted: 09/13/2004] [Indexed: 05/24/2023]
Abstract
L-Galactono-1,4-lactone dehydrogenase (GalLDH; EC 1.3.2.3) is the last enzyme in the putative L-ascorbic acid (AsA) biosynthetic pathway of plants. Here, we show for the first time that the overexpression of GalLDH can increase AsA content in tobacco (Nicotiana tabacum L.) BY-2 cells. To see the effect, we analyzed the properties of these AsA-overproducing transgenic cell lines, especially in relation to AsA content of cells, cell division, senescence and resistance to oxidative stress. The mitotic index in AsA-overproducing cells was higher than in wild-type cells. Moreover, the browning of these cells was markedly restrained, and the proportion of dead cells was reduced, especially in the later period of culture. These AsA-overproducing cells also acquired resistance to paraquat (methyl viologen), which produces active oxygen species. These results contribute to the previous insights about AsA and raise the possibility of the generation of plants that have resistance to environmental stresses by increasing their AsA content.
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Affiliation(s)
- Takaaki Tokunaga
- Graduate School of Biosphere Sciences, Hiroshima University, Kagamiyama, 739-8528, Higashi-Hiroshima, Japan
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241
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Padu E, Kollist H, Tulva I, Oksanen E, Moldau H. Components of apoplastic ascorbate use in Betula pendula leaves exposed to CO2 and O3 enrichment. THE NEW PHYTOLOGIST 2005; 165:131-141. [PMID: 15720628 DOI: 10.1111/j.1469-8137.2004.01220.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Here, the aim was to estimate loads imposed on the apoplastic ascorbate (ASC) pool by enzymatic and nonenzymatic reactions in Betula pendula exposed to doubled CO2 and O3 concentrations in open-top chambers. Leaf apoplastic extracts were analysed for peroxidase and oxidase activities in vitro, using different substrates. Partial loads in vivo were deduced using measured kinetic constants and substituted-enzyme catalysis approaches. Ascorbate use in O3 scavenging was calculated using measured stomatal conductances and ASC concentrations. Under elevated O3, stomatal conductance and O3 uptake were higher. O3 fluxes to the plasmalemma were levelled off by higher apoplastic ASC concentrations. The effect of CO2 enrichment on ASC concentrations under elevated O3 was minor. Under ambient O3, the ascending hierarchy of ASC users was: peroxidases, O3 scavenging, oxidases, coniferyl alcohol re-reduction. Under elevated O3, ASC use in O3 scavenging was higher than by oxidases. The redox state of ASC was not depressed by O3; there was no leaf injury. The cell wall/plasmalemma/cytosol system in birch had sufficient capacity to maintain ASC redox status in the apoplast, without necessity to restrict O3 uptake by stomatal closure.
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Affiliation(s)
- E Padu
- Institute of Molecular and Cell Biology, University of Tartu, Tartu, Estonia
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242
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Functions and homeostasis of zinc, copper, and nickel in plants. TOPICS IN CURRENT GENETICS 2005. [DOI: 10.1007/4735_96] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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243
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Chou WM, Shigaki T, Dammann C, Liu YQ, Bhattacharyya MK. Inhibition of phosphoinositide-specific phospholipase C results in the induction of pathogenesis-related genes in soybean. PLANT BIOLOGY (STUTTGART, GERMANY) 2004; 6:664-72. [PMID: 15570470 DOI: 10.1055/s-2004-830351] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The inositol 1,4,5-trisphosphate (IP3) content is decreased in soybean cells following infection with Pseudomonas syringae pv. glycinea (Psg). In this investigation, a differential display approach was applied to isolate soybean genes that are transcriptionally up-regulated by the inhibition of phosphoinositide-specific phospholipase C (PI-PLC) activity and to study if the transcription of those genes is altered following Psg infection. Four genes, transcriptionally activated following treatment with the PI-PLC-specific inhibitor U-73122, were cloned. Three of the four genes were induced following infection with Psg. The transcripts of a hydrolase homologue (GmHy) were induced in the incompatible but not compatible soybean-Psg interaction. The transcripts of a putative ascorbate oxidase gene (GmAO) were induced in both compatible and incompatible interactions. GmHy and GmAO may represent new classes of pathogenesis-related genes. In addition to these two novel genes, homologues of PR-10 and polygalacturonase inhibitor protein (GmPR10 and GmPGIP, respectively) were identified. These two genes have previously been reported as pathogenesis-related. Transcripts of GmPR-10, but not GmPGIP, were induced in both compatible and incompatible soybean-Psg interactions. Induction of these genes, except for GmPGIP, following inhibition of PI-PLC by either the U-73122 treatment or bacterial infection suggests that PI-PLC may negatively regulate the expression of defence genes.
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Affiliation(s)
- W-M Chou
- Plant Biology Division, The Samuel Roberts Noble Foundation, P.O. Box 2180, Ardmore, Oklahoma 73402, USA
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244
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Mittler R, Vanderauwera S, Gollery M, Van Breusegem F. Reactive oxygen gene network of plants. TRENDS IN PLANT SCIENCE 2004; 9:490-8. [PMID: 15465684 DOI: 10.1016/j.tplants.2004.08.009] [Citation(s) in RCA: 2926] [Impact Index Per Article: 139.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Affiliation(s)
- Ron Mittler
- Department of Biochemistry, Mail Stop 200, University of Nevada, Reno, NV 89557, USA.
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245
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Barth C, Moeder W, Klessig DF, Conklin PL. The timing of senescence and response to pathogens is altered in the ascorbate-deficient Arabidopsis mutant vitamin c-1. PLANT PHYSIOLOGY 2004; 134:1784-92. [PMID: 15064386 PMCID: PMC419851 DOI: 10.1104/pp.103.032185] [Citation(s) in RCA: 165] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2003] [Revised: 11/25/2003] [Accepted: 11/25/2003] [Indexed: 05/18/2023]
Abstract
The ozone-sensitive Arabidopsis mutant vitamin c-1 (vtc1) is deficient in l-ascorbic acid (AsA) due to a mutation in GDP-Man pyrophosphorylase (Conklin et al., 1999), an enzyme involved in the AsA biosynthetic pathway (Smirnoff et al., 2001). In this study, the physiology of this AsA deficiency was initially investigated in response to biotic (virulent pathogens) stress and subsequently with regards to the onset of senescence. Infection with either virulent Pseudomonas syringae or Peronospora parasitica resulted in largely reduced bacterial and hyphal growth in the vtc1 mutant in comparison to the wild type. When vitamin c-2 (vtc2), another AsA-deficient mutant, was challenged with P. parasitica, growth of the fungus was also reduced, indicating that the two AsA-deficient mutants are more resistant to these pathogens. Induction of pathogenesis-related proteins PR-1 and PR-5 is significantly higher in vtc1 than in the wild type when challenged with virulent P. syringae. In addition, the vtc1 mutant exhibits elevated levels of some senescence-associated gene (SAG) transcripts as well as heightened salicylic acid levels. Presumably, therefore, low AsA is causing vtc1 to enter at least some stage(s) of senescence prematurely with an accompanying increase in salicylic acid levels that results in a faster induction of defense responses.
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Affiliation(s)
- Carina Barth
- Boyce Thompson Institute for Plant Research, Ithaca, New York 14853, USA
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