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Publications (40)
Nitric oxide (NO) is a gaseous free radical recognized as a ubiquitous signal transducer that contributes to various biological processes in animals. It exerts most of its effects by regulating the activities of various proteins including Ca ²⁺ channels, protein kinases and transcription factors. In plants, studies conducted over the past 10 years...
The necrogenic bacterium Erwinia amylovora responsible for the fire blight disease causes cell death in apple tissues to enrich intercellular spaces with nutrients. Apple leaves contain large amounts of dihydrochalcones (DHCs), including phloridzin and its aglycone phloretin. Previous work showed an important decrease in the constitutive DHCs stock...
Fire blight is a bacterial disease of Maloideae caused by Erwinia amylovora (Ea). This necrogenic enterobacterium uses a type III secretion system (T3SS) to inject type III effectors into the plant cells to cause disease on its susceptible hosts, including economically important crops like apple and pear. The expressions of marker genes of the sali...
Climate change is projected to have a significant ecological impact on natural ecosystems, most notably through direct and
indirect modifications of local precipitation regimes. In addition, anthropic activities such as the removal of vegetation,
soil proofing due to building, the absence of storm drains and crop over-irrigation will all increase t...
Apple (Malus×domestica) leaf phenolics, in particular the three major dihydrochalcones, phloridzin, trilobatin and sieboldin, were studied for their potential contribution to the resistance to Erwinia amylovora, the causative agent of fire blight. The constitutive phenolic compositions of part of a progeny resulting from a cross between two apple g...
Soil flooding is an environmental constraint that is increasingly important for forest ecosystems, affecting tree growth and regeneration. As a result, selection pressure will alter forest diversity and distribution by favouring tree species tolerant of soil oxygen deprivation. Sessile and pedunculate oaks are the most abundant oak species and they...
We reported on the transit and survival of 6 potentially pathogenic bacterial populations in a schist aquifer beneath the Etueffont landfill (France). Total coliforms, Escherichia coli, Enterococci, Pseudomonas aeruginosa, Salmonella and Staphylococcus aureus were monitored for 15 months in groundwater and leachate and coupled to tracer tests in an...
Basic concepts of NO signalling in animalsNO signalling in plantsInterplays between NO and ROSConclusion
AcknowledgementsReferences
Flavonoids are a group of polyphenol compounds with known antioxidant activities. Among them, dihydrochalcones are mainly found in apple leaves (Malus domestica). Glycosylated dihydrochalcones were previously found in large amounts in leaves of two genotypes of Malus with contrasting resistance to fire blight, a bacterial disease caused by Erwinia...
The cellular and molecular adaptations of non-model woody species to environmental changes are still poorly understood. We have cloned and characterised a novel non-symbiotic hemoglobin from oak roots (QpHb1) which exhibits a specific cellular distribution in the root. The QpHb1 gene is strongly expressed in the protoderm and the protoxylem cells i...
Plants are constantly exposed to changes in environmental conditions. During periods of stress, the cellular redox homeostasis is altered as a result of reactive oxygen species accumulation. The change in redox is responsible for the symptoms commonly observed during periods of stress and reflects the phytotoxic nature of oxygen radical accumulatio...
This study presents the isolation and characterization of a novel nonsymbiotic Hb gene from sessile oak (Quercus petraea) seedlings, herein designated QpHb1. The cellular and tissue expression of QpHb1 was analysed by Northern blotting and in situ hybridization. The encoded protein was predicted to consist of 161 amino acid residues, and shares 71...
There is increasing interest in the interactive role between salicylic acid (SA), reactive oxygen species (ROS) and other
plant signalling molecules in regulating cell death in plants. Initial evidence suggested that SA was a potent inhibitor of
heme-containing enzymes such as catalase and ascorbate peroxidase, thus capable of stimulating ROS accum...
Nitric oxide (NO) and hydrogen peroxide (H(2)O(2)) are regulatory molecules in various developmental processes and stress responses. Tobacco (Nicotiana tabacum) leaves exposed to moderate high light dramatically potentiated NO-mediated cell death in catalase-deficient (CAT1AS) but not in wild-type plants, providing genetic evidence for a partnershi...
Sessile oak is a species of great ecological and silvicultural importance in Europe; however, increased frequency and severity
of flooding of forested areas pose a threat to its regeneration. We monitored water relations, root anatomical changes and
the expression of two calmodulin genes (QpCaM) in sessile oak seedlings during a 14-day flooding tre...
Plants adapt to environmental stresses through specific genetic responses. The molecular mechanisms associated with signal transduction, leading to changes in gene expression early in the stress response, are largely unknown. It is clear, however, that gene expression associated with acclimatory responses is sensitive to the redox state of the cell...
Under both natural and agricultural culture conditions, plants are frequently exposed to transient or permanent low O2 levels in the soil atmosphere or soil solution as a consequence of flooding. Thus hypoxia and/or anoxia are environmental stresses commonly encountered by plant root systems. These O2 restriction conditions will have drastic effect...
We initially compared lipid peroxidation profiles in tobacco (Nicotiana tabacum) leaves during different cell death events. An upstream oxylipin assay was used to discriminate reactive oxygen species (ROS)-mediated lipid peroxidation from 9- and 13-lipoxygenase (LOX)-dependent lipid peroxidation. Free radical-mediated membrane peroxidation was meas...
As part of an integrated study on the molecular response of woody plants to flooding, three CaM genes were isolated from oak seedlings (Quercus petraea Liebl.) and characterized. QpCaM-1 was almost exclusively expressed in roots, whereas QpCaM-2 and -3 were more evenly distributed throughout the plant. The present paper documents the differential e...
Flooding is a major issue for plant survival in many regions of the world. Soil inundation induces multiple plant physiological dysfunctions, leading to a decline in plant growth and survival capacity. Some of the most important effects of flooding include a reduction in water and nutrient uptake and a decrease in metabolism. Prolonged soil floodin...
Hydrogen peroxide plays a central role in launching the defense response during stress in plants. To establish a molecular profile provoked by a sustained increase in hydrogen peroxide levels, catalase-deficient tobacco plants (CAT1AS) were exposed to high light (HL) intensities over a detailed time course. The expression kinetics of >14000 genes w...
In transgenic tobacco plants with reduced catalase activity, high levels of hydrogen peroxide (H2O2) can accumulate under photorespiratory conditions. Such a perturbation in H2O2 homeostasis induced cell death in clusters of palisade parenchyma cells, primarily along the veins. Ultrastructural alterations, such as chromatin condensation and disrupt...
Adequate responses to environmental changes are crucial for plant growth and survival. However, the molecular and biochemical mechanisms that orchestrate these responses are still poorly understood and the signaling networks involved remain elusive. A central role for active oxygen species (AOS) during biotic and abiotic stress responses is well-re...
An alternative approach to maintaining indoor air quality may be the biofiltration of air circulated within the space. A biofilter with living botanical matter as the packing medium reduced concentrations of toluene, ethylbenzene, and o-xylene concurrently present at parts per billion (volume) in indoor air. The greatest reduction in concentrations...
Adequate responses to environmental changes are crucial for plant growth and survival. However, the molecular and biochemical mechanisms involved are poorly understood and the signaling networks remain elusive. The accumulation of active oxygen species (AOS) is a central theme during plant responses to both biotic and abiotic stresses. In both situ...
Adaptation to environmental changes is crucial for plant growth and survival. However, the molecular and biochemical mechanisms of adaptation are still poorly understood and the signaling pathways involved remain elusive. Active oxygen species (AOS) have been proposed as a central component of plant adaptation to both biotic and abiotic stresses. U...
Tobacco (Nicotiana tabacum L.) plants grown in vitro for 4 weeks on medium containing 10 μmol/L salicylic acid (SA) displayed enhanced tolerance of a 4.5 h heat-shock at 49 °C. However, 100 μmol/L SA did not enhance thermotolerance, and caused reduced shoot growth and leaf epidermal cell size. Endogenous glucosylated SA content was enhanced in shoo...
Heat-acclimation or salicylic acid (SA) treatments were previously shown to induce thermotolerance in mustard (Sinapis alba L.) seedlings from 1.5 to 4 h after treatment. In the present study we investigated changes in endogenous SA and antioxidants in relation to induced thermotolerance. Thirty minutes into a 1-h heat-acclimation treatment glucosy...
During the 1990's, much evidence has suggested roles for salicylic acid and H2O2 in responses of plants to pathogens. This article reviews recent international research suggesting that these compounds are also involved in responses to abiotic stresses such as extreme temperatures, ozone pollution or UV irradiation. We recently discovered that salic...
Heat-acclimation or salicylic acid (SA) treatments were previously shown to induce thermotolerance in mustard (Sinapis alba L.) seedlings from 1.5 to 4 h after treatment. In the present study we investigated changes in endogenous SA and antioxidants in relation to induced thermotolerance. Thirty minutes into a 1-h heat-acclimation treatment glucosy...
Potato microplants propagated as nodal explants were subjected to heat treatments in vitro similar to those employed in the thermotherapy step of virus eradication procedures. Low concentrations (10−6–10−5 M) of acetylsalicylic acid (ASA) in the culture medium improved (by 3.7-fold) tolerance of a 5-week hightemperature (35°C)
treatment. Furthermor...
Spraying mustard (Sinapis alba L.) seedlings with salicylic acid (SA) solutions between 10 and 500 &mgr;m significantly improved their tolerance to a subsequent heat shock at 55 degreesC for 1.5 h. The effects of SA were concentration dependent, with higher concentrations failing to induce thermotolerance. The time course of thermotolerance induced...
Plants adapt to environmental stresses through specific genetic responses. The molecular mechanisms associated with signal transduction, leading to changes in gene expression early in the stress response, are largely unknown. It is clear, however, that gene expression associated with acclimatory responses is sensitive to the redox state of the cell...
Plant responses to saturation vapour pressure deficit (SVPD) were studied by subjecting black spruce [Picea mariana (Mill) B.S.P.] and jack pine seedlings (Pinus banksiana Lamb.) to humid (0.3 – 0.8 kPa) or dry (2.0 – 2.5 kPa SVPD) regimes for 4 weeks using a computer-controlled environmental
system to control diurnal variation in SVPD. Dry matter...
