0000000001264418
AUTHOR
Claude Humbert
Active oxygen species production in tobacco cells elicited by cryptogein*
We analyse the relationship between active oxygen species (AOS) production and pH changes induced in tobacco cells by cryptogein, a fungal proteinaceous elicitor of defence mechanisms in plants. When tobacco cells were treated with cryptogein, an intracellular acidification, an alkalinization of the extracellular medium and a transient burst of AOS (H 2 O 2 ) were observed. Treatment of elicited cells with either diphenyleneiodonium (DPI), an inhibitor of the neutrophil NADPH oxidase, or Tiron, which scavenges O2 - , abolished AOS production. These data suggest the involvement of a NADPH oxidase-like enzyme leading to H 2 O 2 production through O 2 - dismutation. Although H 2 O 2 production…
INHIBITION OF CELLULAR GROWTH AND STEROID 11β-HYDROXYLATION INRAS-TRANSFORMED ADRENOCORTICAL CELLS BY THE FUNGAL TOXINS BETICOLINS
Abstract The proliferation of GM16 and 4CDTras-transformed newborn rat adrenocortical (RTAC) cells and Y1 mouse adrenal tumor cells was inhibited by beticolins, the fungal toxins extracted fromCercospora beticola, at submicromolar concentrations in a dose-dependent manner. Inhibitory concentrations for half the maximum inhibition were 150, 75 and 25 n M for beticolin-1 and 230, 150 and 50 n M for beticolin-2 in GM16, 4CDT and Y1 cells respectively. Beticolins strongly inhibited the production of 11β-hydroxysteroids on the second and third days of treatment in a dose-dependent manner between 0.1 and 1 μ M . Beticolins were shown by confocal microscopy to be localized in cytoplasmic organelle…
Colonization of tomato root by pathogenic and nonpathogenic Fusarium oxysporum strains inoculated together and separately into the soil.
ABSTRACT In soil, fungal colonization of plant roots has been traditionally studied by indirect methods such as microbial isolation that do not enable direct observation of infection sites or of interactions between fungal pathogens and their antagonists. Confocal laser scanning microscopy was used to visualize the colonization of tomato roots in heat-treated soil and to observe the interactions between a nonpathogenic strain, Fo47, and a pathogenic strain, Fol8, inoculated onto tomato roots in soil. When inoculated separately, both fungi colonized the entire root surface, with the exception of the apical zone. When both strains were introduced together, they both colonized the root surface…
Elicitation of tobacco cells with ergosterol activates a signal pathway including mobilization of internal calcium
Abstract Ergosterol interacts with tobacco suspension ( Nicotiana tabacum ) cells and triggers pH changes of extracellular medium, oxidative burst and synthesis of phytoalexins. Compared with the responses induced by cryptogein, a proteinaceous elicitor from Phytophthora sp., oxidative burst and ΔpH changes were weaker whereas phytoalexin accumulation was higher with ergosterol. Cryptogein stimulated an apparent continuous uptake of external calcium within 40 min, whereas no net uptake of external calcium occurred upon the addition of ergosterol. However, the elicitation with both cryptogein and ergosterol resulted in an increase of the fluorescence of calcium green 1 in cytosol. The use of…
Use of marked strains of pathogenic (FOL8) and protective (FO47) Fusarium oxysporum to visualize their interactions with the tomato root in soil
Several modes of action have been proposed to explain the biocontrol capacity of the Fusarium oxysporum protective strain Fo47, especially competition with the pathogen for root colonization. Confocal microscopy has been used to visualize the interactions between the ransformed strains and the tomato root in soil. A disinfested soil was infested by Fo47 GFP, Fol8 DsRed2, or both fungi together at several concentrations before transplanting tomato seedlings. The general pattern of soil and root colonization was similar for the two fungi, but the saprophytic development of Fo47 was faster than that of the pathogenic strain. Conidia, at the surface of soil particles, germinated as early as 18 …