An integrated proteomic and metabolomic study on the chronic effects of mercury in Suaeda salsa under an environmentally relevant salinity

As an environmental contaminant, mercury is of great concern due to its high risk to environmental and human health. The halophyte Suaeda salsa is the dominant plant in the intertidal zones of the Yellow River Delta (YRD) where has been contaminated by mercury in some places. This study aimed at evaluating the chronic effects of mercury (Hg(2+), 20 µg L(-1)) and the influence of an environmentally relevant salinity (NaCl, 500 mM) on mercury-induced effects in S. salsa. A total of 43 protein spots with significant changes were identified in response to Hg(2+), salinity and combined Hg(2+) and salinity. These proteins can be categorized into diverse functional classes, related to metabolic processes, photosynthesis, stress response, protein fate, energy metabolism, signaling pathways and immunosuppression. Metabolic responses demonstrated that Hg(2+) could disturb protein and energy metabolisms in S. salsa co-exposed with or without salinity. In addition, both antagonistic and synergistic effects between Hg(2+) and salinity were confirmed by differential levels of proteins (magnesium-chelatase and ribulose-l,5-bisphosphate carboxylase/oxygenase) and metabolites (valine, malonate, asparagine, glycine, fructose and glucose) in S. salsa. These findings suggest that a combination of proteomics and metabolomics can provide insightful information of environmental contaminant-induced effects in plants at molecular levels.