Effects of temperature on copper resistance in daf-21 mutant and Hsp90 expression of Caenorhabditis elegans

Abstract

To determine the effects of temperature alterations on copper toxicity and stress response in Caenorhabditis elegans, an aquatic acute toxicity test was utilized to combinations of four temperature levels (15, 20, 25, and 30°C) and four copper concentrations (0, 0.013, 0.13, and 1.3 mM). Endpoints used included 24-h median lethal concentrations (LC50) value, and 90-kDa heat shock proteins (Hsp90) induction. Results showed a significant acceleration in the mortality with increasing temperature and depressed expression in Hsp90 of the presence of copper. Data on LC50 revealed that simultaneous exposure to both copper and heat stress (30°C) was severe. In contrast, subdued reactions to copper were observed in adult nematode exposed to low temperature (15°C). We have discovered that daf-21 mutation adults result in decreased Cu2+ resistance in a 24 h toxicity assay. Significantly weak expression of Hsp90 in C. elegans was observed at high copper stress as LC50 concentration irrespective of temperatures. These results suggest acclimation temperatures caused variations in copper stress of C. elegans, and Hsp90 expression exhibited greater severity with increasing copper concentration. The present study confirms that temperature effectively confounds copper toxicity and needs to be considered for the accurate prediction and assessment of copper-induced toxicity in nematode.