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Flors, Victor

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Flors, Victor
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https://libra.unine.ch/handle/123456789/332

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  • Publication
    Accès libre
    The multifaceted role of ABA in disease resistance
    (2009)
    Ton, Jurriaan
    ;
    Flors, Victor 
    ;
    Mauch-Mani, Brigitte 
    Long known only for its role in abiotic stress tolerance, recent evidence shows that abscisic acid (ABA) also has a prominent role in biotic stress. Although it acts as a negative regulator of disease resistance, ABA can also promote plant defense and is involved in a complicated network of synergistic and antagonistic interactions. Its role in disease resistance depends on the type of pathogen, its specific way of entering the host and, hence, the timing of the defense response and the type of affected plant tissue. Here, we discuss the controversial evidence pointing to either a repression or a promotion of resistance by ABA. Furthermore, we propose a model in which both possibilities are integrated.
  • Publication
    Accès libre
    Interplay between JA, SA and ABA signalling during basal and induced resistance against Pseudomonas syringae and Alternaria brassicicola
    (2007)
    Flors, Victor 
    ;
    Ton, Jurriaan
    ;
    van Doorn, Ronald
    ;
    Jakab, Gabor
    ;
    García-Agustín, Pilar
    ;
    Mauch-Mani, Brigitte 
    We have examined the role of the callose synthase PMR4 in basal resistance and β-aminobutyric acid-induced resistance (BABA-IR) of Arabidopsis thaliana against the hemi-biotrophic pathogen Pseudomonas syringae and the necrotrophic pathogen Alternaria brassicicola. Compared to wild-type plants, the pmr4-1 mutant displayed enhanced basal resistance against P. syringae, which correlated with constitutive expression of the PR-1 gene. Treating the pmr4-1 mutant with BABA boosted the already elevated levels of PR-1 gene expression, and further increased the level of resistance. Hence, BABA-IR against P. syringae does not require PMR4-derived callose. Conversely, pmr4-1 plants showed enhanced susceptibility to A. brassicicola, and failed to show BABA-IR. Wild-type plants showing BABA-IR against A. brassicicola produced increased levels of JA. The pmr4-1 mutant produced less JA upon A. brassicicola infection than the wild-type. Blocking SA accumulation in pmr4-1 restored basal resistance, but not BABA-IR against A. brassicicola. This suggests that the mutant's enhanced susceptibility to A. brassicicola is caused by SA-mediated suppression of JA, whereas the lack of BABA-IR is caused by its inability to produce callose. A. brassicicola infection suppressed ABA accumulation. Pre-treatment with BABA antagonized this ABA accumulation, and concurrently potentiated expression of the ABA-responsive ABI1 gene. Hence, BABA prevents pathogen-induced suppression of ABA accumulation, and sensitizes the tissue to ABA, causing augmented deposition of PMR4-derived callose.
  • Publication
    Accès libre
    Priming: Getting Ready for Battle
    (2006)
    Conrath, Uwe
    ;
    Beckers, Gerold J. M.
    ;
    Flors, Victor 
    ;
    García-Agustín, Pilar
    ;
    Jakab, Gábor
    ;
    Mauch, Felix
    ;
    Newman, Mari-Anne
    ;
    Pieterse, Corné M. J.
    ;
    Poinssot, Benoit
    ;
    Pozo, María J.
    ;
    Pugin, Alain
    ;
    Schaffrath, Ulrich
    ;
    Ton, Jurriaan
    ;
    Wendehenne, David
    ;
    Zimmerli, Laurent
    ;
    Mauch-Mani, Brigitte 
    Infection of plants by necrotizing pathogens or colonization of plant roots with certain beneficial microbes causes the induction of a unique physiological state called “ priming”. The primed state can also be induced by treatment of plants with various natural and synthetic compounds. Primed plants display either faster, stronger, or both activation of the various cellular defense responses that are induced following attack by either pathogens or insects or in response to abiotic stress. Although the phenomenon has been known for decades, most progress in our understanding of priming has been made over the past few years. Here, we summarize the current knowledge of priming in various induced-resistance phenomena in plants.
  • Publication
    Accès libre
    An Arabidopsis Homeodomain Transcription Factor, OVEREXPRESSOR OF CATIONIC PEROXIDASE 3, Mediates Resistance to Infection by Necrotrophic Pathogens
    (2005)
    Coego, Alberto
    ;
    Ramirez, Vicente
    ;
    Gil, Ma José
    ;
    Flors, Victor 
    ;
    Mauch-Mani, Brigitte 
    ;
    Vera, Pablo
    The mechanisms controlling plant resistance to necrotrophic fungal pathogens are poorly understood. We previously reported on Ep5C, a gene shown to be induced by the H2O2 generated during a plant–pathogen interaction. To identify novel plant components operating in pathogen-induced signaling cascades, we initiated a large-scale screen using Arabidopsis thaliana plants carrying the ß-glucuronidase reporter gene under control of the H2O2-responsive Ep5C promoter. Here, we report the identification and characterization of a mutant, ocp3 (for overexpressor of cationic peroxidase 3), in which the reporter construct is constitutively expressed. Healthy ocp3 plants show increased accumulation of H2O2 and express constitutively the Glutathione S-transferase1 and Plant Defensine 1.2 marker genes, but not the salicylic acid (SA)–dependent pathogenesis-related PR-1 gene. Strikingly, the ocp3 mutant shows enhanced resistance to the necrotrophic pathogens Botrytis cinerea and Plectosphaerella cucumerina. Conversely, resistance to virulent forms of the biotrophic oomycete Hyaloperonospora parasitica and the bacterial pathogen Pseudomonas syringae pv tomato DC3000 remains unaffected in ocp3 plants when compared with wild-type plants. Consistently with this, ocp3 plants are not affected in SA perception and express normal levels of PR genes after pathogen attack. To analyze signal transduction pathways where ocp3 operates, epistasis analyses between ocp3 and pad4, nahG, npr1, ein2, jin1, or coi1 were performed. These studies revealed that the resistance signaling to necrotrophic infection in ocp3 is fully dependent on appropriate perception of jasmonic acid through COI1 and does not require SA or ethylene perception through NPR1 or EIN2, respectively. The OCP3 gene encodes a homeodomain transcription factor that is constitutively expressed in healthy plants but repressed in response to infection by necrotrophic fungi. Together, these results suggest that OCP3 is an important factor for the COI1-dependent resistance of plants to infection by necrotrophic pathogens.
  • Publication
    Accès libre
    Enhancing Arabidopsis Salt and Drought Stress Tolerance by Chemical Priming for Its Abscisic Acid Responses
    (2005)
    Jakab, Gabor
    ;
    Ton, Jurriaan
    ;
    Flors, Victor 
    ;
    Zimmerli, Laurent
    ;
    Métraux, Jean-Pierre
    ;
    Mauch-Mani, Brigitte 
    Drought and salt stress tolerance of Arabidopsis (Arabidopsis thaliana) plants increased following treatment with the nonprotein amino acid -aminobutyric acid (BABA), known as an inducer of resistance against infection of plants by numerous pathogens. BABA-pretreated plants showed earlier and higher expression of the salicylic acid-dependent PR-1 and PR-5 and the abscisic acid (ABA)-dependent RAB-18 and RD-29A genes following salt and drought stress. However, non-expressor of pathogenesis-related genes 1 and constitutive expressor of pathogenesis-related genes 1 mutants as well as transgenic NahG plants, all affected in the salicylic acid signal transduction pathway, still showed increased salt and drought tolerance after BABA treatment. On the contrary, the ABA deficient 1 and ABA insensitive 4 mutants, both impaired in the ABA-signaling pathway, could not be protected by BABA application. Our data demonstrate that BABA-induced water stress tolerance is based on enhanced ABA accumulation resulting in accelerated stress gene expression and stomatal closure. Here, we show a possibility to increase plant tolerance for these abiotic stresses through effective priming of the preexisting defense pathways without resorting to genetic alterations.
  • Publication
    Accès libre
    Dissecting the ß-Aminobutyric Acid–Induced Priming Phenomenon in Arabidopsis
    (2005)
    Ton, Jurriaan
    ;
    Jakab, Gabor
    ;
    Toquin, Valérie
    ;
    Flors, Victor 
    ;
    Iavicoli, Annalisa
    ;
    Maeder, Muriel N.
    ;
    Métraux, Jean-Pierre
    ;
    Mauch-Mani, Brigitte 
    Plants treated with the nonprotein amino acid ß-aminobutyric acid (BABA) develop an enhanced capacity to resist biotic and abiotic stresses. This BABA-induced resistance (BABA-IR) is associated with an augmented capacity to express basal defense responses, a phenomenon known as priming. Based on the observation that high amounts of BABA induce sterility in Arabidopsis thaliana, a mutagenesis screen was performed to select mutants impaired in BABA-induced sterility (ibs). Here, we report the isolation and subsequent characterization of three T-DNA–tagged ibs mutants. Mutant ibs1 is affected in a cyclin-dependent kinase–like protein, and ibs2 is defective in AtSAC1b encoding a polyphosphoinositide phosphatase. Mutant ibs3 is affected in the regulation of the ABA1 gene encoding the abscisic acid (ABA) biosynthetic enzyme zeaxanthin epoxidase. To elucidate the function of the three IBS genes in plant resistance, the mutants were tested for BABA-IR against the bacterium Pseudomonas syringae pv tomato, the oomycete Hyaloperonospora parasitica, and BABA-induced tolerance to salt. All three ibs mutants were compromised in BABA-IR against H. parasitica, although to a different extent. Whereas ibs1 was reduced in priming for salicylate (SA)-dependent trailing necrosis, mutants ibs2 and ibs3 were affected in the priming for callose deposition. Only ibs1 failed to express BABA-IR against P. syringae, which coincided with a defect in priming for SA-inducible PR-1 gene expression. By contrast, ibs2 and ibs3 showed reduced BABA-induced tolerance to salt, which correlated with an affected priming for ABA-inducible gene expression. For all three ibs alleles, the defects in BABA-induced sterility and BABA-induced protection against P. syringae, H. parasitica, and salt could be confirmed in independent mutants. The data presented here introduce three novel regulatory genes involved in priming for different defense responses.