Diuron determines Saccharomyces cerevisiae UE-ME3 survival at beginning of exponential phase.

The diuron is an herbicide used on autumn-winter crops, due to its ability to block the chloroplast electron chain at level of photosystem II. Furthermore, diuron can also exert toxic effects on heterotrophic beings, blocking the respiratory chain and ROS generating. Despite the progressive suppression of diuron application by Directive 200/60/CE, groundwater contamination will still persist. Therefore the main purpose of this work was to evaluate the effect of this phenylurea on S. cerevisiae at proliferative phase. The results show a significant decrease of GSH/GSSG ratio, in cells exposed to 50 mM diuron. Although GR activity does not changes significantly in any assay of this study, it was observed a significantly decrease of G6PD and GPx enzyme activities, in cells grown in 50 and 75 mM diuron. The decline of NADPH availability probably blocks the glutathione cycle, generating oxidative stress. In addition, the CAT T activity presents also a significant increase in cells grown in 50 mM diuron, as well as an increase of cytoplasm ROS, MDA level and CAT A activity in cultures with 50 and 75 mM diuron, that suggests a key role of peroxisomal lipid oxidation in diuron response which cause cell death by an active process