Differential susceptibility to arsenic in glutathione S-transferase omega 2 (GST-O2)-targeted freshwater water flea Daphnia magna mutants

To examine the role of glutathione S-transferase omega class (GST-O2) genes in the biotransformation and detoxification in Daphnia magna, various responses such as in vivo endpoints, arsenic speciation, enzymatic activities, and gene expression pathways related to arsenic metabolism were investigated in wild-type (WT) and GST-O2-mutant-type (MT) fleas produced by CRISPR/Cas9. Sensitivity to arsenic in MT fleas was higher than in WT fleas. Also, the reduction rate of arsenate (AsV) to arsenite (AsIII) in the MT group was significantly lower and led to accumulation of higher arsenic concentrations, resulting in decreased protection against arsenic toxicity. Relative mRNA expression of other GST genes in the GST-O2-targeted MT group generally increased but the enzymatic activity of GST decreased compared with the WT group. Oxidative stress on arsenic exposure was more strongly induced in the MT group compared with the WT group, resulting in a decrease in the ability to defend against toxicity in GST-O2-targeted mutant D. magna. Our results suggest that GST-O2 plays an important role in arsenic biotransformation and detoxification functions in D. magna.

Automated summary

To examine the role of GST-O2 genes in biotransformation and detoxification in Daphnia magna, the study investigated various responses such as in vivo endpoints, arsenic speciation, enzymatic activities, and gene expression pathways. The results showed that MT fleas had higher sensitivity to arsenic and a lower rate of arsenate reduction, leading to higher accumulation of arsenic concentrations and decreased protection against toxicity. The mRNA expression of other GST genes increased but the enzymatic activity of GST decreased in the MT group compared to the WT group. The study highlights the important role of GST-O2 in arsenic biotransformation and detoxification in D. magna.