EFFECTS OF FUNGICIDES ON CHANNELS IN THE FUNGAL MEMBRANE

Effects of fungicides on the water channel and the ion channels in the mycelial membrane of Botrytis cinerea were investigated by the proton nuclear magnetic resonance relaxation time method and cation and anion leakage from the cells. SH inhibitors, such as HgCl2, NEM, captan, PCMBS, and PMA, increased the K+ leakage from the B. cinerea cells. Among them HgCl2, NEM, and captan increased the membrane water permeability of B. cinerea while the organomercuric compounds PCMBS and PMA had no effect on the water permeability. This suggests that a functional SH group of the K+ channel can be attacked by all the SH inhibitors while the water channel in the membrane of B. cinerea has a functional SH group in the hydrophilic environment which only the small hydrophilic SH reactors can access. The Na+ channel and the Cl- channel seem to have no functional SH group which is attacked by SH inhibitors tested here resulting in an increase in the Na+ and Cl- leakage. Ferimzone, which was reported to cause leakage of electrolytes from the P. oryzae cells, had no effect on the water permeability and the ion leakage. Procymidone has been considered to cause some defects in the membrane but had no effect on the ion leakage or the water permeability. Fluazinam decreased the membrane water permeability, suggesting that it blocks the water channel in the membrane. The uncoupling activity of fluazinam reported using rat liver mitochondria was considered to have no direct relation to its effect on the membrane water permeability since the typical uncouplers PCP and CCCP did not decrease the membrane water permeability. © 1993 Academic Press. All rights reserved.