Bee venom genotoxicity on Saccharomyces cerevisiae cells - The role of mitochondria and YAP1 transcription factor.

The present work aims to clarify the genotype differences of a model organism Saccharomyces cerevisiae in response to bee venom. The study evaluated various endpoints including cell survival, induction of physiologically active superoxide anions, mitotic gene conversion, mitotic crossing-over, reverse mutations, DNA double-strand breaks, and Ty1 retrotransposition. The role of the intact mitochondria and the YAP1 transcription factor was also evaluated. Our results indicate a genotype-specific response. The first experimental evidence has been provided that bee venom induces physiologically active superoxide anions and DNA double-strand breaks in S. cerevisiae. The lack of oxidative phosphorylation due to disrupted or missing mitochondrial DNA reduces but not diminishes the cytotoxicity of bee venom. The possible modes of action could be considered direct damage to membranes (cytotoxic effect) and indirect damage to DNA through oxidative stress (genotoxic effect). YAP1 transcription factor was not found to be directly involved in cell defense against bee venom treatment.

Responses of Fraxinus excelsior L. seedlings to ambient ozone exposure in urban and mountain areas based on physiological characteristics and antioxidant activity.

Effects of ozone on the sensitive tree species Fraxinus excelsior L. exposed to ambient air were investigated. The dynamics of photosynthesis, transpiration, stomatal conductance and the activity of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) in three-year-old ash seedlings were studied during a four-month period (June-September). Seedlings were exposed to ambient ozone in an urban (the Central City Park of Sofia - Borisova Gradina) and a mountain (Plana Mountain) area in Bulgaria. The sites were located near climate monitoring stations, providing data on ozone concentrations and meteorological parameters. Ozone exposure at the mountain site (AOT40) was more than two times higher compared to the urban site. Significantly higher values of sun radiation, transpiration, stomatal conductance and enzyme activity at the mountain site were also observed. At the urban site higher values of temperature and air humidity were registered. Effects of the measured variables on ash seedlings were complex and interdependent. No direct effect of ozone concentration in ambient air on the leaf physiology and biochemistry could be proved. However, intensified SOD and CAT activity in the presence of elevated ozone suggested antioxidant reaction in response to ozone uptake.