Responses of duckweed (Lemna minor L.) to aluminum stress: Physiological and proteomics analyses.

Aluminum (Al) is commonly considered an abiotic stress factor under acidic conditions. Duckweed (Lemna minor L.) has wide application in ecotoxicological research as a model organism and, in this study, its response to Al bioaccumulation was evaluated at morphological, physiological and proteomic levels. The Al accumulation in L. minor was accompanied by chlorosis and growth inhibition. Overproduction of superoxide and hydrogen peroxide, and decreased chlorophyll and protein contents, suggested that Al exposure induced oxidative stress. Inhibition of photosynthesis was evident in a significant decrease in maximum photosystem II quantum yield. There were 261 proteins, with significant changes in expression, successfully identified and quantified through isobaric tags for relative and absolute quantification (iTRAQ) analysis. Among the KEGG pathway enrichment proteins, those related to the citrate cycle and amino acid metabolism were predominantly up-regulated, whereas those associated with energy metabolism and glyoxylate and dicarboxylate metabolism were predominantly down-regulated. In addition, antioxidant enzyme related proteins played an important role in the response of L. minor to Al. The western blot analysis further validated the changes in photosynthetic related proteins. These results provide comprehensive insights into the physiological and molecular mechanisms of Al toxicity and tolerance in L. minor.