Anne-marie Pennarun - Academia.edu (original) (raw)
Papers by Anne-marie Pennarun
Plant Physiology and Biochemistry, 1999
Root hairs are a primary site for nutrient absorption and for initiation of signalling processes ... more Root hairs are a primary site for nutrient absorption and for initiation of signalling processes linked to variations of the root environment:plant-microbe interactions or abiotic changes. In many of these cases, the earliest detectable response is the modification of plasma membrane transports, detected through alteration of the electrical membrane potential. In spite of this, root hairs have not been extensively used in electrophysiological research so far. Problems with cell shape and current coupling are often prohibitive for microelectrode voltage-clamp on intact root hairs. In the present study, these difficulties have been overcome and the ion channel currents are described for young root hairs from alfalfa seedlings (Medicago sativa cv Sitel). Electrophysiological and pharmacological studies indicated an inward rectifying K + time-dependent current. This current was sensitive to tetraethylammonium and Cs + (10 mM each). Two other currents never shown in root hairs were described: an outward rectifying time-dependent K + current, inhibited by tetraethylammonium and Cs + (10 mM each) allowing K + efflux under strong depolarizations and an instantaneous inward current identified as an anion current, inhibited by 4-acetamido-4'isothiocyanatostilbene-2,2'-disulfonic acid and anthracene-9-carboxylic acid (100 µM each). These results should contribute to the understanding of root hair development and of signalling processes in M. sativa root hairs. © 1999 Éditions scientifiques et médicales Elsevier SAS
Plant and Cell Physiology, 2005
Brassinosteroids (BRs) are involved in numerous physiological processes associated with plant dev... more Brassinosteroids (BRs) are involved in numerous physiological processes associated with plant development and especially with cell expansion. Here we report that two BRs, 28-homobrassinolide (HBL) and its direct precursor 28homocastasterone (HCS), promote cell expansion of Arabidopsis thaliana suspension cells. We also show that cell expansions induced by HBL and HCS are correlated with the amplitude of the plasma membrane hyperpolarization they elicited. HBL, which promoted the larger cell expansion, also provoked the larger hyperpolarization. We observed that membrane hyperpolarization and cell expansion were partially inhibited by the proton pump inhibitor erythrosin B, suggesting that proton pumps were not the only ion transport system modulated by the two BRs. We used a voltage clamp approach in order to find the other ion transport systems involved in the PM hyperpolarization elicited by HBL and HCS. Interestingly, while anion currents were inhibited by both HBL and HCS, outward rectifying K + currents were increased by HBL but inhibited by HCS. The different electrophysiological behavior shown by HBL and HCS indicates that small changes in the BR skeleton might be responsible for changes in bioactivity.
Molecular Plant-Microbe Interactions, 2006
Fusarium spp. are ubiquitous fungi found in soil worldwide as both pathogenic and nonpathogenic s... more Fusarium spp. are ubiquitous fungi found in soil worldwide as both pathogenic and nonpathogenic strains. The signals leading to disease or the absence of disease are poorly understood. We recently showed that fusaric acid (FA), a nonspecific toxin produced by most Fusarium spp., could elicit various plant defense responses at 100 nM without toxic effect. In this study, we checked for the effect of FA on root and root hairs, probable first site of contact between the fungi and the host. Large FA concentrations reduce root and root-hair growth and induce a rapid transient membrane hyperpolarization, followed by a large depolarization, due to the inhibition of H + -ATPase currents. Nanomolar concentrations of FA induced only an early transient membrane hyperpolarization of root hairs compatible with the induction of a signal transduction pathway. FA at 10 -7 M failed to induce salicylic acid-and jasmonic acid/ethylene-dependent defense-related genes but inhibited the germination of the angiosperm parasite Orobanche ramosa in contact of FA-pretreated Arabidopsis thaliana seedlings. These data suggest that FA at nontoxic concentrations could activate signal transduction components necessary for plant-defense responses that could contribute to biocontrol activity of Fusarium spp.
The Plant Journal, 2000
² Both authors contributed equally to the work.
Plant Physiology and Biochemistry, 1999
Root hairs are a primary site for nutrient absorption and for initiation of signalling processes ... more Root hairs are a primary site for nutrient absorption and for initiation of signalling processes linked to variations of the root environment:plant-microbe interactions or abiotic changes. In many of these cases, the earliest detectable response is the modification of plasma membrane transports, detected through alteration of the electrical membrane potential. In spite of this, root hairs have not been extensively used in electrophysiological research so far. Problems with cell shape and current coupling are often prohibitive for microelectrode voltage-clamp on intact root hairs. In the present study, these difficulties have been overcome and the ion channel currents are described for young root hairs from alfalfa seedlings (Medicago sativa cv Sitel). Electrophysiological and pharmacological studies indicated an inward rectifying K + time-dependent current. This current was sensitive to tetraethylammonium and Cs + (10 mM each). Two other currents never shown in root hairs were described: an outward rectifying time-dependent K + current, inhibited by tetraethylammonium and Cs + (10 mM each) allowing K + efflux under strong depolarizations and an instantaneous inward current identified as an anion current, inhibited by 4-acetamido-4'isothiocyanatostilbene-2,2'-disulfonic acid and anthracene-9-carboxylic acid (100 µM each). These results should contribute to the understanding of root hair development and of signalling processes in M. sativa root hairs. © 1999 Éditions scientifiques et médicales Elsevier SAS
Plant and Cell Physiology, 2005
Brassinosteroids (BRs) are involved in numerous physiological processes associated with plant dev... more Brassinosteroids (BRs) are involved in numerous physiological processes associated with plant development and especially with cell expansion. Here we report that two BRs, 28-homobrassinolide (HBL) and its direct precursor 28homocastasterone (HCS), promote cell expansion of Arabidopsis thaliana suspension cells. We also show that cell expansions induced by HBL and HCS are correlated with the amplitude of the plasma membrane hyperpolarization they elicited. HBL, which promoted the larger cell expansion, also provoked the larger hyperpolarization. We observed that membrane hyperpolarization and cell expansion were partially inhibited by the proton pump inhibitor erythrosin B, suggesting that proton pumps were not the only ion transport system modulated by the two BRs. We used a voltage clamp approach in order to find the other ion transport systems involved in the PM hyperpolarization elicited by HBL and HCS. Interestingly, while anion currents were inhibited by both HBL and HCS, outward rectifying K + currents were increased by HBL but inhibited by HCS. The different electrophysiological behavior shown by HBL and HCS indicates that small changes in the BR skeleton might be responsible for changes in bioactivity.
Molecular Plant-Microbe Interactions, 2006
Fusarium spp. are ubiquitous fungi found in soil worldwide as both pathogenic and nonpathogenic s... more Fusarium spp. are ubiquitous fungi found in soil worldwide as both pathogenic and nonpathogenic strains. The signals leading to disease or the absence of disease are poorly understood. We recently showed that fusaric acid (FA), a nonspecific toxin produced by most Fusarium spp., could elicit various plant defense responses at 100 nM without toxic effect. In this study, we checked for the effect of FA on root and root hairs, probable first site of contact between the fungi and the host. Large FA concentrations reduce root and root-hair growth and induce a rapid transient membrane hyperpolarization, followed by a large depolarization, due to the inhibition of H + -ATPase currents. Nanomolar concentrations of FA induced only an early transient membrane hyperpolarization of root hairs compatible with the induction of a signal transduction pathway. FA at 10 -7 M failed to induce salicylic acid-and jasmonic acid/ethylene-dependent defense-related genes but inhibited the germination of the angiosperm parasite Orobanche ramosa in contact of FA-pretreated Arabidopsis thaliana seedlings. These data suggest that FA at nontoxic concentrations could activate signal transduction components necessary for plant-defense responses that could contribute to biocontrol activity of Fusarium spp.
The Plant Journal, 2000
² Both authors contributed equally to the work.