Specific proteomic response of Unio pictorum mussel to a mixture of glyphosate and microcystin-LR

This proteomic study examined effects of microcystin-LR (a common cyanobacterial toxin) and a commercial glyphosate product on protein regulation in the freshwater mussel Unio pictorum. The U. pictorum used in the study were collected in the field and acclimatized in the laboratory prior to chemical exposure. Mussels were exposed for 7 days to either 10 µg/L glyphosate, 10 µg/L microcystin-LR, or a combination. None of the treatments caused mortality, and all mussels were filtering at the end of the experiment. Digestive glands were removed from mussels and their proteins were analyzed to look for spots with statistical variations as compared to un-exposed mussels that indicated up- or down-regulation of specific proteins. Overall, more proteomic changes were caused by  microcystin-LR than glyphosate. Certain spots also only had a response when exposed to a mixture, indicating an interaction effect of contaminants. Mussels exposed to microcystin-LR or the combination experienced up- and down-regulation of proteins involved in cytoskeleton formation the most, followed by proteins involved in oxidative stress and detoxification, among other pathways. The glyphosate product primarily caused down-regulation of proteins on its own, but only one of these proteins was identifiable and was found to be involved in cytoskeleton formation. The authors emphasize that their study highlights the importance of examining multi-contaminants, and of looking at sublethal effects of contaminants at low concentrations.