| Salt stress is one of the major abiotic stresses that disturbs the growth and developmen of plants and even causes the death of plants, especially leads to serious agricultural production reduction. Therefore, to study the mechanism of plant salt tolerance and to explore new methods and strategies to improve plants salt stress resistance is of great practical significance.Hydrogen sulfide (H2S) is a colorless gas with rotten egg smell. Low concentration of H2S has important regulation function on plant growth and development as well as the tolerance to a variety of stress including heavy metal, cold and heat, drought and salt. However, most of these studies focus on the physiological and biochemical level, the study on the mechanisms of H2S alleviates plant tolerance to salt stress at the proteomic and molecular level remain unclear.In the present study, rice (Oryza sativa), an important crop, as the material and the methods of comparative proteomics and combined with the determination of physiological parameters were used to performe the comprehensive study on the molecular mechanism of H2S alleviates salt stress at proteomic level. Following are the main results.(1) The result of gradient experiment of NaHS showed that the H2S-alleviated salt response was H2S concentration dependent, i.e., the treatment with low concentration of NaHS could alleviate salt stress. However the treatment with high concentration of NaHS increased the damages to plants. We found that100μM NaHS was the optimal concentration to alleviate the negative effects of100mM NaCl on three-day-treated rice seedling.(2) H2S could alleviate growth inhibition induced by salt stress in rice. After the application of extrogenous H2S, the reductions of root length, plant height, biomass of root and arial part caused by salt stress were relieved. Furthermore, we found that H2S affected the morphogenesis of rice root. (3) The activities of SOD and POD increased, but the activities of CAT and APX reduced in rice leaves by salt stress, while the contents of MDA, O2-and H2O2were significantly decreased. Furthermore, we also found that GSH content was increased but the GST activity was reduced under salt stress. H2S may adjust the antioxidant enzyme activity and accumulate more GSH to alleviate oxidative damage caused by salt stress.(4) We successfully identified92differentially expressed proteins among CK, NaCl, and NaCl+H2S treated rice seedling leaves. Based on Venn diagram and clustering diagram analysis, we found that some proteins were down-regulated under salt stress, but were recovered and even up-regualted with extrogenous H2S application. Differentially expressed proteins can be divided into seven categories according to their functions, including photosynthesis related proteins, material and energy metabolism related proteins, protein synthesis, folding, transportation and degradation related proteins, antioxidant and detoxifying related proteins, stress response and defense related proteins and a small number of unknown proteins. These differentially expressed proteins are involved in various metabolic pathways in plants, which signify H2S enhanced salt tolerance of rice seedling through multiple mechanisms. Subcellular localization analysis showed that most of the differentially expressed proteins were located in cytoplasm and chloroplast, a part of them were located in mitochondria, very few proteins were located in other locations.(5) The gene expressions of several selected differentially expressed proteins showed the change patterns at protein level and transcriptional level were not consistent exactly, suggesting that H2S alleviates rice seedling salt stress through different mechanisms at protein level and transcription level.In conclusion, according to the functions and the change patterns of identified differentially expressed proteins and combined with the determination of physiological parameters, we speculated that H2S functions in salt tolerance in rice seedlings. Firstly, exogenous H2S reduced salt-induced oxidative stress and relieved the inhibition of photosynthesis under salt stress. Secondly, under H2S treatment, the energy productions of rice seedlings were enchanced and metabolisms of various materials were altered and the material and energy metabolisms are the foundations of salt resistance for rice. Finally, strengthened cellular structure including the remolding of cytoskeleton and cell wall lignification and recovered protein synthesis, enchanced folding and transportation of functional proteins as well as accelerated degradation of damaged proteins also involved in improving salt stress in rice seedlings. |
PDF Full Text Request