Protein Expression And Respiratory Metabolism Response To Low Temperature During Wheat Seed Germination

With the aggravation of global climate changed, and corn’s variety improvement tendency in Huanghe-Huaihe-Haihe(HHH) zone turned to the direction of expanding the growth period and late harvest, proportion of late sown wheat expanded year by year.Late-sown winter wheat is vulnerable to low temperature in germination process. Using the physiological-biochemical and high-throughput proteomics technology, we studied differential proteomic both at optimum(20℃) and low(10℃) temperature during wheat seed germination, which is of important theoretical and practical significance in clarifying the influence of temperature on wheat seed germination and its mechanism of action, and in exploring the mechanism of plant cold tolerance mechanism and its precautionary measure.Jimai 22, a wheat variety(Triticum aestivum L.), germinate both at optimum(20℃) and low(10 ℃) temperatures. Samples were taken from four important germination stages(dry seeds before germination, rapid water-absorption stage, slow water-absorption stage, growth water-absorption stage) for measuring respiratory rate, starch content and soluble sugar content. Being separated by two-dimensional electrophoresis, differential protein spots were analyzed by image analysis software, and to study the discrepant proteins and involved in biological function protein identification by MALDI-TOF/TOF-MS and database analysis.The main results were as follows:1. The water uptake of seeds at low temperature was slower than at optimum temperature, so low temperature delayed the process of seed germination. Compared with different germination temperature under the same germination stage, the respiratory rate and rise of wheat seed were significantly higher in 20℃ than that in 10℃. The soluble sugar content in wheat seed were decreased first and then increased, both reached the minimum in the stage of slow water absorption; compared with different germination temperature under the same germination stage, changes of soluble sugar content of wheat seed was significantly faster in 20℃ than that in 10℃. The total starch content was lower in optimum temperature than that in low temperature, drop of the total starch content in optimum temperature was significantly higher than that in low temperature.2. Under the condition of two different temperatures, we got 56 differential expressionproteins and 46 protein spots which matched the search of the database. Making analysis of variance statistical test on the content of proteins, these proteins included 22 regulated protein(U1-U22), 18 down-regulated protein(D1-D18), and 6 complex Protein(C1-C6). The identified proteins mainly involved in energy metabolism, carbohydrate metabolism, protein metabolism, storage proteins, inhibition protein, transfer and transcription. In this proteins,up-regulated protein mainly related with energy metabolism(9), carbohydrate metabolism(15),and protein metabolism related enzymes(2), etc., down-regulated protein mainly associated with storage protein(8), inhibition of protein(7), etc.3. During seed germination, expression quantity of β-amylase was on the rise, at the same time, α-amylase-B-isozyme appeared at the slow absorption stage and its expression quantity increased rapidly along with that of β-amylase. At the same germination stage the expression quantity of the starch enzyme under low temperature were less than that under optimum temperature. Energy metabolism related proteins mainly included enzyme proteins related with glycolysis, the citric acid cycle and ATP synthesis. Expression quantity of these enzymes protein were up-regulated in the germination process, and the expression level under optimum temperature was higher than that under low temperature. Which indicating that the material and energy metabolism under optimal temperature started earlier and the level of activity was higher than that under the low temperature. Starch synthesis enzymes and a large number of synthetic enzymes were degraded during germination, which indicating that the synthesis of polysaccharides during germination stopped or remained at a low level.Expression quantity of storage proteins during the germination process mainly trend to down-regulated and drop significantly at low temperatures compared to optimum temperature.Expression quantity of inhibition protein expressed down-regulated during seed germination,and the expression level under low temperatures were higher than that under the optimum temperature.4. Analysis by synthesis. Compared with optimum temperature, low temperature inhibited the degradation of starch by restricting the expression of α-amylase and β-amylase,and restrained respiration by reducing the expression of phosphoglycerate mutase in glycolytic pathway, citrate synthase and malate dehydrogenase in TCA, dihydrolipoyl dehydrogenase and ATP synthase, which resulted in significantly lower respiratory rate at low temperature during seed germination. It also restrained the degradation of inhibitory protein that include storage protein, α-amylase/trypsin inhibitor, serpin and xylanase inhibitor to prevent other metabolic reactions.