| Salicylic acid (SA) is a novel phenolic hormone and important signaling molecule, and regulates most processes of plant growth and development. As a signal molecule, it plays an important role in improving plant resistance to biotic stresses, and the research about this aspect was deep and comprehensive. In recent years, it has been found that SA significantly improves the plant resistance to abiotic stresses. These reports are mainly involved in its resistant mechanism at physiological level, but few at molecular level.In the present study, the positive SA concentrations improving the wheat abiotic resistance were screened out, and the proteomic mechanisms on positive and negative SA concentrations were further explored.The main results of this study are as follows:1. Wheat seedlings were cultivated in Hoagland’s solution with SA different concentrations (0, 0.1, 0.25, 0.5, 0.75, 1.0, 2.0 and 3.0 mM) for 3 d. The results indicated that, compared to the control (0 mM SA), wheat seedlings grew faster with SA (0.25 mM~0.75 mM) treatments , and these seedlings were characterizaed with green leaves, higher heights, heavier fresh and dry weights and higher contens of the chlorophyll, but fewer malonaldehyde (MDA) content . Among these concentrations, 0.5 mM was the best positive effect. However, more than 2 mM SA inhibited the growth of wheat seedlings characterized with shorter roots, yellow leaves and higher MDA contents.2. Wheat seedings pretreated by 0 (control), 0.5 and 3 mM SA were sufferred to salt stress (250 mM NaCl) to verify the above results to treatment. Under the salt stress, heights, fresh and dry weights, and the chlorophyll contents of wheat seedling prtreated with 0.5 mM SA were higher than that control with CK, but MDA contents in these plants were lower than those in CK. This implied that 0.5 mM SA alleviated the damage caused by salt stress. Heights, fresh and dry weighst, and chlorophyll contents of seedlings pretreated with 3 mM under salt stress, were significantly lower than those of CK, but MDA contents were higher, suggesting that SA high concentrations accelerated salt stress. This further verified results of the above exprements. 3. The method of two-dimensional gel electrophoresis on wheat leaves was optimized in the present study. The results showed that high-quality proteins from wheat leaves were extracted using TCA/acetone method than phenol extraction method. Two-dimensional electrophoresis maps of proteins extraceted using TCA/acetone method had many points with clear map background. Under conditions of pH 4-7 linear IPG strips of 24 cm, 1000μg sample and 85000 Vhr, proteins were seperated better and good protein maps with high quality were gained.4. Using this optimized wheat two-dimensional electrophoresis method, proteomic profiles of wheat seedlings pretreated with 0.5 and 3 mM SA were explored. The results showed that most of the protein plots differentially expressed were among the pH 4-7 region, and 15 protein spots with differential expression were harvested. LC/ESI-MS/MS and protein database analysis indicated that 1,5-ribulose bisphosphate decarboxylase /oxygenase large subunit, Rubisco large subunit-binding proteinαsubunits, ferredoxi- n-NADP(H) oxidoreductase, Cu/Zn superoxide dismutase were up-regulated in leaves of wheat seedling pretreated with 0.5 mM SA, but decrease in those pretreated with 3 mM SA. Serine/threonine protein kinase and ATP synthase subunits were up-regulated in wheat seedlings pretreated with both 0.5 and 3.0 mM SA. However, a ferredoxin -NADP (H) oxidoreductase and an unknown protein were down-regulated in wheat seedlings pretreated with both 0.5 and 3.0 mM SA. Glutamine synthase subunit was up-regulated only in 3.0 mM SA pretreatment. Accordingly, it was speculated that these proteins could be closely associated with changes in stress resistance of wheat plants by SA different concentrantions. |
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