Cadmium-Induced Metallothionein Production and Antioxidative Responses Differentially Influence γ-Ray Sensitivity Among Saccharomyces cerevisiae Strains

Cadmium (Cd) exerts multiple toxic effects on yeast cells, including the inactivation of essential proteins and the induction of oxidative damage through the generation of reactive oxygen species (ROS). To mitigate Cd-derived ROS generation, Saccharomyces cerevisiae activates metallothionein (MT) production. Because γ-ray irradiation is also known to generate ROS, we investigated how Cd-induced MT production and antioxidative responses influence γ-ray sensitivity in S. cerevisiae; Six strains were examined: BY4741; IM3, a high-manganese-accumulating derivative of BY4741; NA87-11A; OY, a commercial baker’s yeast; K7, the sake-brewing strain; and EC1118, the wine-brewing strain. The effects of Cd exposure were tested on growth, MT gene expression, γ-ray-irradiation sensitivity and ROS production across these strains. The γ-ray tolerance and MT-gene expression were increased by Cd exposure in three laboratory strains and the baker’s yeast strain, but not in the two brewing strains. Conversely, the MT-gene expression was decreased in the brewing strains. These findings suggest that brewing strains of S. cerevisiae possess unique genetic and regulatory characteristics that limit their capacity to activate antioxidant defenses. Such insights will also aid in the design and improvement of yeast strains with enhanced tolerance to ROS production.