THE CA-45(2-VIRIDE MYCELIUM - CORRELATION WITH GROWTH AND CONIDIATION() UPTAKE BY TRICHODERMA)

The properties of Ca2+ uptake by Trichoderma viride were studied using radionuclide Ca-45(2+) in conjunction with the study of effects of ag ents influencing the Ca2+ homeostasis on the Ca-45(2+) uptake, vegetat ive growth and conidiation. Mycelium of T. viride was found to take up Ca-45(2+) in time- and temperature-dependent manner. The Ca-45(2+) up take could be distinguished from the Ca-45(2+) binding by the insensit ivity to washing with EGTA (ethylene glycol-bis(2-amino ethyl ether)-N ,N,N',N'-tetraacetic acid)-containing solution. Tire Ca-45(2+) uptake was only slightly suppressed by the treatment used to de-energize cell s. Agents known to influence Ca2+ homeostasis in animal and plant cell s were also active in perturbing the Ca2+ homeostasis in T. viride. In this respect, the agents tested had dual (stimulatory or inhibitory) effects on tire Ca-45(2+) uptake. No clear correlation among the pertu rbation of the Ca-45(2+) uptake and the inhibition of growth and conid iation was found for the group of compounds tested. Sr2+ and Mg2+ inhi bited Ca-45(2+) uptake but did not inhibit growth and conidiation. Co2 +, Cd2+ inhibited both Ca-45(2+) uptake and growth. Other agents teste d (CU2+, Ni2+, La3+, dihydropyridines), which inhibited growth of T. v iride, induced massive Cl-45(2+) uptake by its mycelium. Ba2+ and Mn2 showed a biphasic effect on Ca-45(2+) uptake-inhibition at lower, and stimulation at higher concentrations, but they had only a slight inhi bitory effect on the growth or conidiation at higher concentrations. T he Ca-45(2+) uptake was influenced by addition of monovalent cations t o a small extent only. Na+ (up to 75 mmol.l(-1)), less than K+, slight ly suppressed the Ca-45(2+) up- take leaving both growth and conidiati on unaffected. Upon depriving the fungus of Ca2+ by chelation of extra cellular Ca2+ (not Mg2+ or divalent, trace metals) by EGTA, which inte rfered with Ca2+ homeostasis, vegetative growth rate, and starvation-i nduced conidiation were restricted. These results suggest that the sus tained Ca2+ influx occurs across the T. viride plasma membrane which m ay 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.