The 45Ca2+ uptake by Trichoderma viride mycelium. Correlation with growth and conidiation.
The properties of Ca2+ uptake by Trichoderma viride were studied using radionuclide 45Ca2+ in conjunction with the study of effects of agents influencing the Ca2+ homeostasis on the 45Ca2+ uptake, vegetative growth and conidiation. Mycelium of T. viride was found to take up 45Ca2+ in time- and temperature-dependent manner. The 45Ca2+ uptake could be distinguished from the 45Ca2+ binding by the insensitivity to washing with EGTA (ethylene glycol-bis(2-amino ethyl ether)-N,N,N',N'-tetraacetic acid)-containing solution. The 45Ca2+ uptake was only slightly suppressed by the treatment used to de-energize cells. Agents known to influence Ca2+ homeostasis in animal and plant cells were also active in perturbing the Ca2+ homeostasis in T. viride. In this respect, the agents tested had dual (stimulatory or inhibitory) effects on the 45Ca2+ uptake. No clear correlation among the perturbation of the 45Ca2+ uptake and the inhibition of growth and conidiation was found for the group of compounds tested. Sr2+ and Mg2+ inhibited 45Ca2+ uptake but did not inhibit growth and conidiation. Co2+, Cd2+ inhibited both 45Ca2+ uptake and growth. Other agents tested (Cu2+, Ni2+, La3+, dihydropyridines), which inhibited growth of T. viride, induced massive 45Ca2+ uptake by its mycelium. Ba2+ and Mn2+ showed a biphasic effect on 45Ca2+ uptake-inhibition at lower, and stimulation at higher concentrations, but they had only a slight inhibitory effect on the growth or conidiation at higher concentrations. The 45Ca2+ uptake was influenced by addition of monovalent cations to a small extent only. Na+ (up to 75 mmol.l-1), less than K+, slightly suppressed the 45Ca2+ uptake leaving both growth and conidiation unaffected. Upon depriving the fungus of Ca2+ by chelation of extracellular Ca2+ (not Mg2+ or divalent trace metals) by EGTA, which interfered with Ca2+ homeostasis, vegetative growth rate, and starvation-induced conidiation were restricted. These results suggest that the sustained Ca2+ influx occurs across the T. viride plasma membrane which may be a target site for the antifungal action of heavy metal ions, and its perturbation may lead to disturbances in physiological processes including growth and conidiation. The properties of the Ca2+ influx in T. viride observed substantially differ from those observed in animal cells.
Krystofová
S
S
Department of Microbiology, Biochemistry and Biology, Slovak Technical University, Bratislava, Slovakia.
Varecka
L
L
Betina
V
V
D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002132:Calcium Radioisotopes; D002413:Cations, Divalent / Q000494:pharmacology; D002414:Cations, Monovalent / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D006706:Homeostasis; D007700:Kinetics; D007811:Lanthanum / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D013324:Strontium / Q000494:pharmacology; D014242:Trichoderma / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*
D002121:Calcium Channel Blockers; D002132:Calcium Radioisotopes; D002413:Cations, Divalent; D002414:Cations, Monovalent; D004533:Egtazic Acid; D007811:Lanthanum; D008274:Magnesium; D002118:Calcium; D013324:Strontium