Silver nanoparticles (Ag-NPs) are excessively used as antibacterial agents; however, environmental interaction specifically with the plants remain uncertain. To study the size-dependent effects of Ag-NPs on soybean under flooding, a proteomic technique was used. Morphological analysis revealed that treatment with Ag-NPs of 15 nm promoted soybean growth under flooding compared to 2 and 50-80 nm. A total of 228 common proteins that significantly changed in abundance under flooding without and with Ag-NPs of 2,15, and 50-80 nm. Under varying sizes of Ag-NPs, number of protein synthesis related proteins decreased compared to flooding while number of amino acid synthesis related proteins were increased under Ag-NPs of 15 nm. Hierarchical clustering identified the ribosomal proteins that increased under Ag-NPs of 15 nm while decreased under other sizes. In silico protein-protein interaction indicated the beta ketoacyl reducatse 1 as the most interacted protein under Ag-NPs of 15 nm while least interacted under other sizes. The beta ketoacyl reductase 1 was up-regulated under Ag-NPs of 15 nm while its enzyme activity was decreased. These results suggest that the different sizes of Ag-NPs might affect the soybean growth under flooding by regulating the proteins related to amino acid synthesis and wax formation.
Biological significance: This study highlighted the response of soybean proteins towards varying sizes of Ag NPs under flooding stress using gel-free proteomic technique. The Ag NPs of 15 nm improved the length of root including hypocotyl of soybean. The proteins related to protein metabolism, cell division/organization, and amino acid metabolism were differentially changed under the varying sizes of Ag NPs. The protein synthesis-related proteins were decreased while amino acid metabolism-related proteins were increased under varying sizes of Ag NPs. The ribosomal proteins were increased under Ag NPs of 15 nm. The beta ketoacyl reductase I was identified as the most interacted protein under varying sizes of Ag NPs. The mRNA expression level of beta ketoacyl reductase was up-regulated under Ag NPs of 15 nm while its activity was decreased. These results suggest that the Ag NPs of 15 nm improved the soybean growth under flooding stress by increasing the proteins related to amino acid synthesis and waxes formation. (C) 2016 Elsevier B.V. All rights reserved.