Proteomic analysis on sodium nitroprusside induced NaCl tolerance in barley seedlings

The salinization of agricultural soils poses a serious challenge in worldwide. Different strategies have been developed to improve salt tolerance of plants. Although it has been shown that exogenous sodium nitroprusside (SNP) administration can alleviate the harmful effects of salinity and promote plants salt tolerance, the roles of SNP in regulating proteomic changes have not been fully understood. For this purpose, comparative proteomic analysis were performed on leaf tissues of barley seedlings exposed to NaCl and / or SNP applications in order to better understand the responses of barley (Horedum vulgare L.) seedlings to salt stress and to understand the protective roles of exogenous SNP in alleviating salt-induced damage. The results showed that exogenous SNP application restored the seedling growth inhibited by NaCl stress. Proteomic analysis indicated that 24 proteins were differentially expressed under SNP and/or NaCl stress treatments. Among them, 15 proteins were successfully identified by MALDI-TOF/TOF mass spectrometry. Gene ontology analysis revealed that several pathways were regulated by SNP and/or NaCl treatments, including photosynthesis, protein metabolism, stress defense, and energy metabolism. Exogenous SNP treatment was increased the expression levels of 20 kDa chaperonin, proteasome subunit beta type-2, 2-Cys peroxiredoxin BAS1, thiazole biosynthetic enzyme 1-1, ferredoxin-NADP reductase, S-adenosylmethionine synthetase 3, and elongation factor Tu proteins in the leaves of barley seedlings under salt stress. The present results suggest that SNP may alleviate NaCl-induced growth inhibition through regulation of photosynthesis, degradation of misfolded/damaged proteins, activation of stress defense, and the promoting of the synthesis of polyamines, proline and GABA. This study is the first to provide insights at the proteomic level into the molecular mechanism of SNP in response to salt stress in barley seedlings.