Insufficiency of Copper Ion Homeostasis Causes Freeze-Thaw Injury of Yeast Cells

ABSTRACT: Saccharomyces cerevisiae is exposed to freeze-thaw stress in commercial processes including frozen dough baking. The cell viability and fermentation activity after freeze-thaw were dramatically decreased due to freeze-thaw injury. Because freeze-thaw injury involves complex phenomena, the mechanisms of it are not fully understood. We attempted to analyze the mechanisms of freeze-thaw injury by indirect gene expression analysis during post-thaw incubation after freeze-thaw treatment using DNA microarray profiling. The results showed that a high frequency of the genes involved in the homeostasis of metal ions were up-regulated depending on the freezing period. The phenotype of the deletion mutants of the up-regulated genes extracted by indirect gene expression analysis was assessed. The deletion strains of the MAC1 and CTR1 genes involved in copper ion homeostasis exhibited freeze-thaw sensitivity, suggesting that copper ion homeostasis is required for freeze-thaw tolerance. Supplementation with copper ions during post-thaw incubation increased intracellular superoxide dismutase activity. Inverse correlated with intracellular superoxide dismutase activity, intracellular levels of reactive oxygen species were decreased. Moreover, cell viability increased by supplementation with copper ions under specific assessment conditions. This study suggested that insufficiency of copper ion homeostasis may be one of the causes of freeze-thaw injury. Total RNA was extracted from the stress-treated yeast cells by using a hot phenol method. Poly(A)+ RNA was enriched from total RNA by using an Oligotex dT30 (Super) mRNA purification kit (Takara Bio, Ohtsu, Japan). cDNA synthesis, cRNA synthesis, and labeling were performed according to the Affymetrix user’s manual (Affymetrix, Santa Clara, USA). Biotinyated cRNA was fragmented and then used as a probe.Affimetrix Yeast Genome 2.0 arrays (Affymetrix) were used as DNA microarrays. All experiments were done in triplicate independently.

ORGANISM(S): Saccharomyces cerevisiae

SUBMITTER: Jun Shima 

PROVIDER: E-GEOD-15461 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress