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Ca2+ fluxes in developing Trichoderma viride mycelium.

M Simkovic·S Krystofová·L Varecka
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Abstract

The properties of both Ca2+ influx and efflux in the mycelium during the life cycle of Trichoderma viride were studied by means of 45Ca2+ and by X-ray fluorescence spectroscopy measurements. The properties of the 45Ca2+ influx and effluxes indicate that they are mediated by different transport systems. The Ca2+ influx could be mediated by an electrogenic Ca2+/nH+ antiport, or by an Ca2+ uniport system. Both Ca2+ influx and efflux were stimulated by the uncouplers (and the treatment leading to the suppression of energy metabolism) and by azalomycin F, an antifungal agent. Salicylate stimulated the Ca2+ efflux, but inhibited the Ca2+ influx. In the isolated preparation of crude vacuolar/mitochondrial fraction, salicylate induced the Ca2+ release, as did A23187. Azalomycin F moderately released Ca2+ from the microsomal fraction. On the other hand, uncouplers did not release Ca2+ from the isolated organelles, but inhibited to a different extent the ATP-dependent and -independent Ca2+ influx. The results could be explained in terms of the capacitative Ca2+ influx mechanism. The rate of 45Ca2+ influx, or of the 40Ca2+ content, was maximal after about 30 h of submerged cultivation, and then decreased. The results show that loading of internal Ca2+ stores occurs in the early stages of the development of mycelium only, and the Ca2+ influx mechanism is developmentally down-regulated, being almost nonexistent during its later stages. In older mycelium, growth seems to be autonomous of the extracellular Ca2+ until the onset of conidiation.

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Anti-Bacterial AgentsCalcimycinCalciumCalcium RadioisotopesCarbonyl Cyanide p-TrifluoromethoxyphenylhydrazoneHydrogen-Ion ConcentrationIonophoresMacrolidesSalicylatesSpectrometry, X-Ray EmissionSubcellular FractionsTemperatureTime FactorsTrichodermaUncoupling AgentsJournal ArticleResearch Support, Non-U.S. Gov't

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M Simkovic, S Krystofová, L Varecka. 2000. Ca2+ fluxes in developing Trichoderma viride mycelium.. https://doi.org/10.1139/w99-139

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