Efeito dos fungicidas mancozeb, captan e dithianon sobre Saccharomyces cerevisiae

Abstract

Fungicides are currently used to control fungal phytopathogenic diseases in many crops, including fruits. These compounds, especially those described as multisite activity fungicides, can affect non-target organisms like yeasts leading to their cell death by different pathways. The objective of this work was determining the mechanism of action and death of three fungicides used in viticulture (captan, dithianon and mancozeb) on Saccharomyces cerevisiae. The results showed that yeast exposition to the mancozeb (100 µM, 6 h) lead to a drastic reduction of cell viability, but no modification of cell membrane integrity. Mancozeb treated cells shown apoptotic markers as increase of intracellular reactive oxygen species (ROS), mitochondrial membrane hyperpolarization, and phosphatidylserine externalization, indicating that mancozeb induced cell death in S. cerevisiae is apoptotic and as shown by mutants strains, follow metacaspase-dependent pathway. Almost 80% of captan treated yeasts (20 µM, 6 h) showed citoplasmatic membrane dysfunction, and a drastic reduction on both non-proteic and proteic thiol concentrations. Moreover, the cells that retain their membrane integrity after exposure to the captan exhibited phosphatidylserine externalization and ROS accumulation, indicating apoptosis. YCA1 deletion mutant exhibited partial resistance to captan, suggesting a metacaspase dependent apoptotic cascade. In wine fermentations captan (2,5 µM) delays the beginning of alcoholic fermentations in a dose dependent manner, associated with a drastic reduction on yeast viability. However, in sub-lethal dosages, the reminiscent viable cells adapted to the fungicide, grow and complete fermentation with non-evident modifications on the physicochemical characteristics of the final product. Similarly, yeast cells treated with dithianon (2 µM; 3 h) showed cell membrane permeabilization, ROS increase, and decrease of cellular thiol compounds, but no signs of apoptosis. In general, the results indicated that mancozeb induces metacaspase dependent apoptotic cell death in S. cerevisiae, where captan leads to a dual necrotic and apoptotic cell death, and dithianon kills cells by necrosis.