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Legumes display common and host-specific responses to the rhizobial cellulase CelC2 during primary symbiotic infection. Sci Rep 2019; 9:13907. [PMID: 31554862 PMCID: PMC6761101 DOI: 10.1038/s41598-019-50337-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 09/02/2019] [Indexed: 01/08/2023] Open
Abstract
Primary infection of legumes by rhizobia involves the controlled localized enzymatic breakdown of cell walls at root hair tips. Previous studies determined the role of rhizobial CelC2 cellulase in different steps of the symbiotic interaction Rhizobium leguminosarum-Trifolium repens. Recent findings also showed that CelC2 influences early signalling events in the Ensifer meliloti-Medicago truncatula interaction. Here, we have monitored the root hair phenotypes of two legume plants, T. repens and M. sativa, upon inoculation with strains of their cognate and non-cognate rhizobial species, R. leguminosarum bv trifolii and E. meliloti, (over)expressing the CelC2 coding gene, celC. Regardless of the host, CelC2 specifically elicited ‘hole-on-the-tip’ events (Hot phenotype) in the root hair apex, consistent with the role of this endoglucanase in eroding the noncrystalline cellulose found in polarly growing cell walls. Overproduction of CelC2 also increased root hair tip redirections (RaT phenotype) events in both cognate and non-cognate hosts. Interestingly, heterologous celC expression also induced non-canonical alterations in ROS (Reactive Oxygen Species) homeostasis at root hair tips of Trifolium and Medicago. These results suggest the concurrence of shared unspecific and host-related plant responses to CelC2 during early steps of symbiotic rhizobial infection. Our data thus identify CelC2 cellulase as an important determinant of events underlying early infection of the legume host by rhizobia.
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Robledo M, Menéndez E, Jiménez-Zurdo JI, Rivas R, Velázquez E, Martínez-Molina E, Oldroyd G, Mateos PF. Heterologous Expression of Rhizobial CelC2 Cellulase Impairs Symbiotic Signaling and Nodulation in Medicago truncatula. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2018; 31:568-575. [PMID: 29334470 DOI: 10.1094/mpmi-11-17-0265-r] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The infection of legume plants by rhizobia is tightly regulated to ensure accurate bacterial penetration, infection, and development of functionally efficient nitrogen-fixing root nodules. Rhizobial Nod factors (NF) have key roles in the elicitation of nodulation signaling. Infection of white clover roots also involves the tightly regulated specific breakdown of the noncrystalline apex of cell walls in growing root hairs, which is mediated by Rhizobium leguminosarum bv. trifolii cellulase CelC2. Here, we have analyzed the impact of this endoglucanase on symbiotic signaling in the model legume Medicago truncatula. Ensifer meliloti constitutively expressing celC gene exhibited delayed nodulation and elicited aberrant ineffective nodules, hampering plant growth in the absence of nitrogen. Cotreatment of roots with NF and CelC2 altered Ca2+ spiking in root hairs and induction of the early nodulin gene ENOD11. Our data suggest that CelC2 alters early signaling between partners in the rhizobia-legume interaction.
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Affiliation(s)
- Marta Robledo
- 1 Departamento de Microbiología y Genética, Centro Hispano-Luso de Investigaciones Agrarias, Universidad de Salamanca, Unidad Asociada CSIC/USAL, Spain
- 2 Estación Experimental del Zaidín, CSIC, Granada, Spain; and
| | - Esther Menéndez
- 1 Departamento de Microbiología y Genética, Centro Hispano-Luso de Investigaciones Agrarias, Universidad de Salamanca, Unidad Asociada CSIC/USAL, Spain
| | | | - Raúl Rivas
- 1 Departamento de Microbiología y Genética, Centro Hispano-Luso de Investigaciones Agrarias, Universidad de Salamanca, Unidad Asociada CSIC/USAL, Spain
| | - Encarna Velázquez
- 1 Departamento de Microbiología y Genética, Centro Hispano-Luso de Investigaciones Agrarias, Universidad de Salamanca, Unidad Asociada CSIC/USAL, Spain
| | - Eustoquio Martínez-Molina
- 1 Departamento de Microbiología y Genética, Centro Hispano-Luso de Investigaciones Agrarias, Universidad de Salamanca, Unidad Asociada CSIC/USAL, Spain
| | - Giles Oldroyd
- 3 Department of Cell and Development Biology, John Innes Centre, Norwich, U.K
| | - Pedro F Mateos
- 1 Departamento de Microbiología y Genética, Centro Hispano-Luso de Investigaciones Agrarias, Universidad de Salamanca, Unidad Asociada CSIC/USAL, Spain
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Daneshkhah R, Grundler FMW, Wieczorek K. The Role of MPK6 as Mediator of Ethylene/Jasmonic Acid Signaling in Serendipita indica-Colonized Arabidopsis Roots. PLANT MOLECULAR BIOLOGY REPORTER 2018; 36:284-294. [PMID: 29875545 PMCID: PMC5966479 DOI: 10.1007/s11105-018-1077-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Serendipita indica is an axenically cultivable fungus, which colonizes a broad range of plant species including the model plant Arabidopsis thaliana. Root colonization by this endophyte leads to enhanced plant fitness and performance and promotes resistance against different biotic and abiotic stresses. The involvement of MPK6 in this mutualistic interaction had been previously shown with an mpk6 A. thaliana mutant, which failed to respond to S. indica colonization. Here, we demonstrate that mpk6 roots are significantly less colonized by S. indica compared to wild-type roots and the foliar application of plant hormones, ethylene, or jasmonic acid, restores the colonization rate at least to the wild-type level. Further, hormone-treated mpk6 plants show typical S. indica-induced growth promotion effects. Moreover, expression levels of several genes related to plant defense and hormone signaling are significantly changed at different colonization phases. Our results demonstrate that the successful root colonization by S. indica depends on efficient suppression of plant immune responses. In A. thaliana, this process relies on intact hormone signaling in which MPK6 seems to play a pivotal role.
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Affiliation(s)
- R. Daneshkhah
- Division of Plant Protection, Department of Crop Sciences, University of Natural Resources and Life Sciences, Konrad-Lorenz-Straße 24, 3430 Tulln on the Danube, Austria
| | - F. M. W. Grundler
- Institute of Crop Science and Resource Conservation, Molecular Phytomedicine, University Bonn, Karlrobert-Kreiten-Str. 13, 53115 Bonn, Germany
| | - Krzysztof Wieczorek
- Division of Plant Protection, Department of Crop Sciences, University of Natural Resources and Life Sciences, Konrad-Lorenz-Straße 24, 3430 Tulln on the Danube, Austria
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Koers S, Guzel-Deger A, Marten I, Roelfsema MRG. Barley mildew and its elicitor chitosan promote closed stomata by stimulating guard-cell S-type anion channels. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2011; 68:670-80. [PMID: 21781196 DOI: 10.1111/j.1365-313x.2011.04719.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Stomatal closure is known to be associated with early defence responses of plant cells triggered by microbe-associated molecular patterns (MAMPs). However, the molecular mechanisms underlying these guard-cell responses have not yet been elucidated. We therefore studied pathogen-induced changes in ion channel activity in Hordeum vulgare guard cells. Barley mildew (Blumeria graminis) hyphae growing on leaves inhibited light-induced stomatal opening, starting at 9 h after inoculation, when appressoria had developed. Alternatively, stomatal closure was induced by nano-infusion of chitosan via open stomata into the sub-stomatal cavity. Experiments using intracellular double-barreled micro-electrodes revealed that mildew stimulated S-type (slow) anion channels in guard cells. These channels enable the efflux of anions from guard cells and also promote K(+) extrusion by altering the plasma membrane potential. Stimulation of S-type anion channels was also provoked by nano-infusion of chitosan. These data suggest that MAMPs of mildew hyphae penetrating the cuticle provoke activation of S-type anion channels in guard cells. In response, guard cells extrude K(+) salts, resulting in stomatal closure. Plasma membrane anion channels probably represent general targets of MAMP signaling in plants, as these elicitors depolarize the plasma membrane of various cell types.
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Affiliation(s)
- Sandra Koers
- Molecular Plant Physiology and Biophysics, Julius-von-Sachs Institute for Biosciences, Biocenter, Würzburg University, Julius-von-Sachs Platz 2, D-97082 Würzburg, Germany
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5
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Aidemark M, Tjellström H, Sandelius AS, Stålbrand H, Andreasson E, Rasmusson AG, Widell S. Trichoderma viride cellulase induces resistance to the antibiotic pore-forming peptide alamethicin associated with changes in the plasma membrane lipid composition of tobacco BY-2 cells. BMC PLANT BIOLOGY 2010; 10:274. [PMID: 21156059 PMCID: PMC3017840 DOI: 10.1186/1471-2229-10-274] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Accepted: 12/14/2010] [Indexed: 05/24/2023]
Abstract
BACKGROUND Alamethicin is a membrane-active peptide isolated from the beneficial root-colonising fungus Trichoderma viride. This peptide can insert into membranes to form voltage-dependent pores. We have previously shown that alamethicin efficiently permeabilises the plasma membrane, mitochondria and plastids of cultured plant cells. In the present investigation, tobacco cells (Nicotiana tabacum L. cv Bright Yellow-2) were pre-treated with elicitors of defence responses to study whether this would affect permeabilisation. RESULTS Oxygen consumption experiments showed that added cellulase, already upon a limited cell wall digestion, induced a cellular resistance to alamethicin permeabilisation. This effect could not be elicited by xylanase or bacterial elicitors such as flg22 or elf18. The induction of alamethicin resistance was independent of novel protein synthesis. Also, the permeabilisation was unaffected by the membrane-depolarising agent FCCP. As judged by lipid analyses, isolated plasma membranes from cellulase-pretreated tobacco cells contained less negatively charged phospholipids (PS and PI), yet higher ratios of membrane lipid fatty acid to sterol and to protein, as compared to control membranes. CONCLUSION We suggest that altered membrane lipid composition as induced by cellulase activity may render the cells resistant to alamethicin. This induced resistance could reflect a natural process where the plant cells alter their sensitivity to membrane pore-forming agents secreted by Trichoderma spp. to attack other microorganisms, and thus adding to the beneficial effect that Trichoderma has for plant root growth. Furthermore, our data extends previous reports on artificial membranes on the importance of lipid packing and charge for alamethicin permeabilisation to in vivo conditions.
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Affiliation(s)
- Mari Aidemark
- Department of Biology, Lund University, Sölvegatan 35, SE-223 62 LUND, Sweden
| | - Henrik Tjellström
- Plant Biology Department, Michigan State University, East Lansing, 48824, MI, USA
- Department of Plant and Environmental Sciences, Göteborg University, P.O. Box 461, SE-405 30 Göteborg, Sweden
| | - Anna Stina Sandelius
- Department of Plant and Environmental Sciences, Göteborg University, P.O. Box 461, SE-405 30 Göteborg, Sweden
| | - Henrik Stålbrand
- Department of Biochemistry, P.O. Box 124, SE-221 00 Lund, Sweden
| | - Erik Andreasson
- Department of Plant Protection Biology, Swedish Agricultural University, P.O. Box 102, SE-230 53 Alnarp, Sweden
| | - Allan G Rasmusson
- Department of Biology, Lund University, Sölvegatan 35, SE-223 62 LUND, Sweden
| | - Susanne Widell
- Department of Biology, Lund University, Sölvegatan 35, SE-223 62 LUND, Sweden
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Vadassery J, Ranf S, Drzewiecki C, Mithöfer A, Mazars C, Scheel D, Lee J, Oelmüller R. A cell wall extract from the endophytic fungus Piriformospora indica promotes growth of Arabidopsis seedlings and induces intracellular calcium elevation in roots. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2009; 59:193-206. [PMID: 19392691 DOI: 10.1111/j.1365-313x.2009.03867.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Calcium (Ca2+), as a second messenger, is crucial for signal transduction processes during many biotic interactions. We demonstrate that cellular [Ca2+] elevations are early events in the interaction between the plant growth-promoting fungus Piriformospora indica and Arabidopsis thaliana. A cell wall extract (CWE) from the fungus promotes the growth of wild-type seedlings but not of seedlings from P. indica-insensitive mutants. The extract and the fungus also induce a similar set of genes in Arabidopsis roots, among them genes with Ca2+ signalling-related functions. The CWE induces a transient cytosolic Ca2+ ([Ca2+](cyt)) elevation in the roots of Arabidopsis and tobacco (Nicotiana tabacum) plants, as well as in BY-2 suspension cultures expressing the Ca2+ bioluminescent indicator aequorin. Nuclear Ca2+ transients were also observed in tobacco BY-2 cells. The Ca2+ response was more pronounced in roots than in shoots and involved Ca2+ uptake from the extracellular space as revealed by inhibitor studies. Inhibition of the Ca2+ response by staurosporine and the refractory nature of the Ca2+ elevation suggest that a receptor may be involved. The CWE does not stimulate H2O2 production and the activation of defence gene expression, although it led to phosphorylation of mitogen-activated protein kinases (MAPKs) in a Ca2+-dependent manner. The involvement of MAPK6 in the mutualistic interaction was shown for an mpk6 line, which did not respond to P. indica. Thus, Ca2+ is likely to be an early signalling component in the mutualistic interaction between P. indica and Arabidopsis or tobacco.
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Affiliation(s)
- Jyothilakshmi Vadassery
- Friedrich-Schiller-Universität Jena, Institut für Allgemeine Botanik und Pflanzenphysiologie, Dornburger Street 159, D-07743 Jena, Germany
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7
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Levchenko V, Guinot DR, Klein M, Roelfsema MRG, Hedrich R, Dietrich P. Stringent control of cytoplasmic Ca2+ in guard cells of intact plants compared to their counterparts in epidermal strips or guard cell protoplasts. PROTOPLASMA 2008; 233:61-72. [PMID: 18648729 DOI: 10.1007/s00709-008-0307-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2007] [Accepted: 01/28/2008] [Indexed: 05/26/2023]
Abstract
Cytoplasmic calcium elevations, transients, and oscillations are thought to encode information that triggers a variety of physiological responses in plant cells. Yet Ca(2+) signals induced by a single stimulus vary, depending on the physiological state of the cell and experimental conditions. We compared Ca(2+) homeostasis and stimulus-induced Ca(2+) signals in guard cells of intact plants, epidermal strips, and isolated protoplasts. Single-cell ratiometric imaging with the Ca(2+)-sensitive dye Fura 2 was applied in combination with electrophysiological recordings. Guard cell protoplasts were loaded with Fura 2 via a patch pipette, revealing a cytoplasmic free Ca(2+) concentration of around 80 nM at -47 mV. Upon hyperpolarization of the plasma membrane to -107 mV, the Ca(2+) concentration increased to levels exceeding 400 nM. Intact guard cells were able to maintain much lower cytoplasmic free Ca(2+) concentrations at hyperpolarized potentials, the average concentration at -100 mV was 183 and 90 nM in epidermal strips and intact plants, respectively. Further hyperpolarization of the plasma membrane to -160 mV induced a sustained rise of the guard cell cytoplasmic Ca(2+) concentration, which slowly returned to the prestimulus level in intact plants but not in epidermal strips. Our results show that cytoplasmic Ca(2+) concentrations are stringently controlled in guard cells of intact plants but become increasingly more sensitive to changes in the plasma membrane potential in epidermal strips and isolated protoplasts.
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Affiliation(s)
- V Levchenko
- Molecular Plant Physiology and Biophysics, Julius von Sachs Institute for Biosciences, Würzburg University, Würzburg
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8
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Dumas B, Bottin A, Gaulin E, Esquerré-Tugayé MT. Cellulose-binding domains: cellulose associated-defensive sensing partners? TRENDS IN PLANT SCIENCE 2008; 13:160-164. [PMID: 18329320 DOI: 10.1016/j.tplants.2008.02.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2007] [Revised: 02/01/2008] [Accepted: 02/04/2008] [Indexed: 05/26/2023]
Abstract
The cellulose-binding domains (CBDs) in the Phytophthora cellulose-binding elicitor lectin (CBEL) are potent elicitors of plant defence responses. Induction of defence has also been reported in various cellulose-deficient mutants of Arabidopsis thaliana. Based on these observations, we propose a model linking cellulose alteration to defence induction. This integrates the fast increase in cytosolic calcium recorded in response to CBEL, mechano-stimulated calcium uptake mechanisms, and proteins that interact functionally with the cellulose synthase complex. In this context, CBDs emerge as new tools to decipher the signalling cascades that result from cell wall-cellulose perturbations.
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Affiliation(s)
- Bernard Dumas
- Unité Mixte de Recherche 5546 Centre National de la Recherche Scientifique-Université Paul Sabatier Toulouse III, Pôle de Biotechnologie Végétale, 24 Chemin de Borde-Rouge, BP42617 Auzeville, 31326 Castanet-Tolosan, France
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9
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Gauthier A, Lamotte O, Reboutier D, Bouteau F, Pugin A, Wendehenne D. Cryptogein-induced anion effluxes: electrophysiological properties and analysis of the mechanisms through which they contribute to the elicitor-triggered cell death. PLANT SIGNALING & BEHAVIOR 2007; 2:86-95. [PMID: 19516973 PMCID: PMC2633904 DOI: 10.4161/psb.2.2.4015] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2007] [Accepted: 02/15/2007] [Indexed: 05/23/2023]
Abstract
Anion effluxes are amongst the earliest reactions of plant cells to elicitors of defence responses. However, their properties and their role in disease resistance remain almost unknown. We previously demonstrated that cryptogein, an elicitor of tobacco defence responses, induces a nitrate (NO(3) (-)) efflux. This efflux is an early prerequisite to the cryptogein-triggered hypersensitive response (HR). Here, we analyzed the electrophysiological properties of the elicitor-mediated NO(3) (-) efflux and clarified the mechanisms through which it contributes to cell death. Application of the discontinuous single electrode voltage-clamp technique in tobacco cells elicited with cryptogein enabled us to record the activation of slow-type deactivating anion channel currents. Cryptogein-induced plasma membrane depolarization and Ca(2+) influx, an essential component of elicitor signalling for HR cell death, were prevented by inhibiting the NO(3) (-) efflux. Similarly, pharmacological blocking of the anion efflux suppressed vacuolar collapse, a hallmark of cell death. The role of NO(3) (-) efflux in mediating proteases activation was further assessed. It is shown that cryptogein induced the activation of three proteases with apparent molecular masses of 95, 190 and 240 kDa. Their activation occurred independently on the anion efflux and, together with cell death, was strongly reduced by cycloheximide and the protease inhibitor PMSF. In contrast, the NO(3) (-) efflux was shown to promote the accumulation of transcripts encoding vacuolar processing enzymes, a family of proteases previously reported to contribute to the disruption of vacuole integrity observed during the HR. Collectively, our data indicate that anion efflux is an early prerequisite to morphological and biochemical events participating to cell death.
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Affiliation(s)
- Adrien Gauthier
- Université de Bourgogne; Plante-Microbe-Environnement; Dijon, France
| | | | - David Reboutier
- Laboratoire d'Electrophysiologie des Membranes; Université Paris; Paris, France
| | - François Bouteau
- Laboratoire d'Electrophysiologie des Membranes; Université Paris; Paris, France
| | - Alain Pugin
- Université de Bourgogne; Plante-Microbe-Environnement; Dijon, France
| | - David Wendehenne
- Université de Bourgogne; Plante-Microbe-Environnement; Dijon, France
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10
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Bouizgarne B, El-Maarouf-Bouteau H, Frankart C, Reboutier D, Madiona K, Pennarun AM, Monestiez M, Trouverie J, Amiar Z, Briand J, Brault M, Rona JP, Ouhdouch Y, El Hadrami I, Bouteau F. Early physiological responses of Arabidopsis thaliana cells to fusaric acid: toxic and signalling effects. THE NEW PHYTOLOGIST 2006; 169:209-18. [PMID: 16390432 DOI: 10.1111/j.1469-8137.2005.01561.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Fusaric acid (FA) is a toxin produced by Fusarium species. Most studies on FA have reported toxic effects (for example, alteration of cell growth, mitochondrial activity and membrane permeability) at concentrations greater than 10(-5) m. FA participates in fungal pathogenicity by decreasing plant cell viability. However, FA is also produced by nonpathogenic Fusarii, potential biocontrol agents of vascular wilt fusaria. The aim of this study was to determine whether FA, at nontoxic concentrations, could induce plant defence responses. Nontoxic concentrations of FA were determined from cell-growth and O2-uptake measurements on suspensions of Arabidopsis thaliana cells. Ion flux variations were analysed from electrophysiological and pH measurements. H2O2 and cytosolic calcium were quantified by luminescence techniques. FA at nontoxic concentrations (i.e. below 10(-6) m) was able to induce the synthesis of phytoalexin, a classic delayed plant response to pathogen. FA could also induce rapid responses putatively involved in signal transduction, such as the production of reactive oxygen species, and an increase in cytosolic calcium and ion channel current modulations. FA can thus act as an elicitor at nanomolar concentrations.
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Affiliation(s)
- B Bouizgarne
- LEM (EA 3514), Université Paris 7, 2, Place Jussieu, 75251 Paris cedex 05, France
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11
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Felle HH, Herrmann A, Hückelhoven R, Kogel KH. Root-to-shoot signalling: apoplastic alkalinization, a general stress response and defence factor in barley (Hordeum vulgare). PROTOPLASMA 2005; 227:17-24. [PMID: 16389490 DOI: 10.1007/s00709-005-0131-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2005] [Accepted: 05/31/2005] [Indexed: 05/06/2023]
Abstract
We used a noninvasive microprobe technique to record in substomatal cavities of barley leaves the apoplastic pH response to different stress situations. When K+ (or Na+) activity at the roots of intact plants was increased from 1 to 50 mM, the leaf apoplastic pH increased by 0.4 to 0.6 units within 8 to 12 min when stomata were open, and within 15 to 20 min when stomata were closed. This reaction was accompanied by a correlative increase in K+ activity. Addition of 1 microM abscisic acid caused an apoplastic alkalinization of 0.5 to 0.8 units, and low temperatures (4 degrees C) increased pH by 0.2 to 0.3 units. Addition of 100 mM sorbitol or pH changes in the range 4.0 to 7.9 had no effect, ruling out that osmotic potential and/or pH is the carried signal. On detached leaves, the same treatments yielded qualitatively similar results, suggesting that the xylem is the most likely signal path. Following the attack of powdery mildew, the apoplastic pH of barley leaves substantially increases. We demonstrate that in susceptible barley, pretreatment (soil drench) with the resistance-inducing chemical benzo- (1,2,3)thiadiazole-7-carbothioic acid S-methyl ester markedly enhances this pH response. This is consistent with previous finding that apoplastic alkalinization is related to the degree of resistance towards this fungus.
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Affiliation(s)
- H H Felle
- Botanisches Institut I, Justus-Liebig-Universität, Giessen, Federal Republic of Germany.
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12
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Zuppini A, Navazio L, Sella L, Castiglioni C, Favaron F, Mariani P. An endopolygalacturonase from Sclerotinia sclerotiorum induces calcium-mediated signaling and programmed cell death in soybean cells. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2005; 18:849-55. [PMID: 16134897 DOI: 10.1094/mpmi-18-0849] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
A basic endopolygalacturonase (PG) isoform, produced early by Sclerotinia sclerotiorum when infecting soybean seedlings, was used to examine the signaling role of the enzyme in aequorin-expressing soybean cells. A cytosolic Ca2+ elevation was induced, with a rapid increase (phase 1) and a very slow decrease (phase 2) of Ca2+ concentration, indicating the involvement of Ca2+ ions in PG signaling. Within 1 h of PG-cell contact a remarkable level of cell death was recorded, significantly higher than the control cell culture turnover. The observed morphological and biochemical changes were indicative of the activation of programmed cell death; in particular, cytochrome c release in the cytoplasm and activation of both caspase 9-like and caspase 3-like proteases were found. When a polygalacturonase-inhibiting protein (PGIP) and the PG were simultaneously applied to cells, both the Ca2+ increase and cell death were annulled. The possible roles of prolonged sustained cytosolic Ca2+ concentrations in inducing cell death and of the PG-PGIP interaction in preventing PG signaling are discussed.
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Affiliation(s)
- Anna Zuppini
- Dipartimento di Biologia, Università di Padova, via U Bassi 58/B, 35131 Padova, Italy
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13
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Reboutier D, Frankart C, Vedel R, Brault M, Duggleby RG, Rona JP, Barny MA, Bouteau F. A CFTR chloride channel activator prevents HrpN(ea)-induced cell death in Arabidopsis thaliana suspension cells. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2005; 43:567-72. [PMID: 15936204 DOI: 10.1016/j.plaphy.2005.03.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2005] [Accepted: 03/17/2005] [Indexed: 05/02/2023]
Abstract
Erwinia amylovora is a necrogenic bacterium that causes fire blight of the Maloideae subfamily of Roseacae, such as apple and pear. It provokes necrosis in aerial parts of susceptible host plants and the typical hypersensitive reaction in non-host plants. The secreted harpin, HrpN ea, is able by itself to induce an active cell death in non-host plants. Ion flux modulations were shown to be involved early in such processes but very few data are available on the plasma membrane ion channel activities responsible for the pathogen-induced ion fluxes. We show here that HrpN ea induces cell death in non-host Arabidopsis thaliana suspension cells. We further show that two cystic fibrosis transmembrane conductance regulator modulators, glibenclamide and bromotetramisole, can regulate anion channel activities and HrpN ea-induced cell death.
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Affiliation(s)
- David Reboutier
- LEM, EA 3514, Université Paris 7, Case 7069, 2, place Jussieu, 75251 Paris cedex 5, France.
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14
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Felle HH, Herrmann A, Hanstein S, Hückelhoven R, Kogel KH. Apoplastic pH signaling in barley leaves attacked by the powdery mildew fungus Blumeria graminis f. sp. hordei. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2004; 17:118-23. [PMID: 14714875 DOI: 10.1094/mpmi.2004.17.1.118] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
To investigate apoplastic responses of barley (Hordeum vulgare L.) to the barley powdery mildew fungus Blumeria graminis f. sp. hordei, noninvasive microprobe techniques were employed. H(+)- and Ca(2+)-selective microprobes were inserted into open stomata of barley leaves inoculated with Blumeria graminis f. sp. hordei race A6 conidia. Resistance gene-mediated responses of barley genotype Ingrid (susceptible parent line) and the near-isogenic resistant Ingrid backcross lines (I-mlo5, I-Mla12, and I-Mlg) were continuously monitored from 20 min to 4 days after inoculation. The main events were categorized as short-term responses around 2 h after inoculation (hai), intermediate responses around 8 and 12 hai, and long-term responses starting between 21 and 24 hai. Short-term responses were rapid transient decreases of apoplastic H(+)- and Ca2+ activities that lasted minutes only. Kinetics were similar for all genotypes tested, and thus, these short-term responses were attributed as nonspecific first encounters of fungal surface material with the host plasma membrane. This is supported by the observation that a microinjected chitin oligomer (GlcNAc)8 yielded similar apoplastic alkalinization. Intermediate responses are trains of H+ (increase) spikes that, being different in susceptible Ingrid and penetration-resistant I-mlo5 (or I-Mlg), were interpreted as accompanying specific events of papillae formation. Long-term events were massive slow and long-lasting alkalinizations up to two pH units above control. Since these latter changes were only observed with near-isogenic hypersensitive reaction (HR)-mounting genotypes I-Mla12 and I-Mlg but not with I-mlo5 or, to a smaller extent, with susceptible Ingrid, both lacking significant rates of HR, they were rated as cell death specific. It is concluded that apoplastic pH changes are important indicators of host-pathogen interactions that correlate with both the different stages of fungal development and the different types of host defense response.
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Affiliation(s)
- Hubert H Felle
- Botanisches Institut I, Justus-Liebig-Universität, Senckenbergstrasse 17, D-35390 Giessen, Germany
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