Global cytosine methylation in Daphnia magna depends on genotype, environment and their interaction

The authors characterized global cytosine methylation levels in two different genotypes of the ecotoxicological model organism Daphnia magna after exposure to a wide array of biotic and abiotic environmental stressors. The study aimed to improve the authors' understanding of the role of cytosine methylation in the organism‘s response to environmental conditions. The authors observed a significant genotype effect, an environment effect and a genotype x environment effect. In particular, global cytosine methylation levels were significantly altered after exposure to Triops predation cues, Microcystis and sodium chloride compared to control conditions. Significant differences between the two genotypes were observed when animals were exposed to Triops predation cues, Microcystis, Cryptomonas and sodium chloride. Despite the low global methylation rate under control conditions (0.49-0.52%), global cytosine methylation levels upon exposure to Triops demonstrated a five-fold difference between the genotypes (0.21% versus 1.02%). No effects were found in response to arsenic, cadmium, fish, lead, pH of 5.5, pH of 8, temperature, hypoxia and white fat cell disease. The authors’ results point to the potential role of epigenetic effects under changing environmental conditions such as predation (i.e. Triops), diet (i.e. Cryptomonas and Microcystis) and salinity. The current results indicate that, despite global cytosine methylation levels are low, epigenetic effects may be important in environmental studies on Daphnia. This article is protected by copyright. All rights reservedstatus: publishe