Investigation On Mechanism Of Changes In Protein Of Wheat Seeds During After-ripening

Three varieties newly harvested wheat seeds with different gluten contents were used to analyze germination, processing characteristics, flour quality, ROS contents, ROS-processing systems, contents and composition of protein at the specific time during after-ripening. Moreover, SDS-PAGE, 2-DE were used to study the state of thiol and the variations in protein subunits. In addition, in order to prove the effect of ROS on physiological after-ripening and the expression of protein, wheat seeds harvested 15 d imbibed 6h in the present of 0.2m M MV to generate ROS processing. The results were as follows:The germination of wheat seeds increased gradually with the extension of after-ripening. And ZM366, AK58, ZM004 completed physiological after-ripening at 90 d, 75 d, 45 d after harvested respectively. The moisture contents of ZM004 showed a downward trend, but moisture contents of ZM366 and AK58 increased slightly. While the change of hardness was not significant. The changes in weight and diameter were consistent. And the weight and diameter of ZM366, ZM004 decreased slightly. However, the changes in weight and diameter of AK58 were not significant.The flour extraction rates of wheat seeds with different gluten fluctuated with a slight upward trend during after-ripening. Moreover, the flour yield of 1M+2M increased with the extension of after-ripening. The whiteness of flour increased slightly in early period of after-ripening, and tended to be stable in the late. Besides, the falling number increased during after-ripening. And the falling number of ZM366, AK58 tended to be stable at 60 d after harvested. Moreover, changes in contents of wet, dry gluten were not significantly. But the gluten index increased significantly in the early period of after-ripening, and tended to be stable in 60 d, 75 d, 45 d after harvested respectively. The SDS-sedimentation values of ZM366 ZM004 increased significantly in the early period of after-ripening, and tended to be stable at 75 d after harvested. But the SDS-sedimentation values of AK58 did not change significantly. The Development time decreased significantly. And the Farinograph water absorption, softening degree increased during after-ripening. So the stability and resistant mixing characteristics improved in some degree.O₂^- and H₂O₂ contents increased at the initial stage of wheat seeds after-ripening and then decreased, finally maintained a stable level. And a significantly positive correlation existed between the contents of O₂^- and the increase of germination rate. Moreover, treatment in the present of 0.2m M MV, which induced O₂^- production, strengthened the germination rate of dormant wheat seeds. Data also showed that ROS metabolism was active during after-ripening. What’s more, a significant positive correlation existed between NADPH oxidase activities and O₂^-contents. And SOD activities and O₂^-contents showed a significant negative correlation. So NADPH oxidase and SOD played more important roles than POD in ROS accumulation during wheat seeds after-ripening.The results showed that the impact of after-ripening on the total protein content was not significant. But the extraction rates of albumin, globulin, gliadin decreased with the extension of storage time and then stayed at a stable level. The extraction rates of gluten and the ratio of glutenin / gliadin increased at the early stage of after-ripening, then stayed at a stable level later.The contents of free sulfhydryl group decreased and disulfide bond contents increased There was an exchange reaction between free sulfhydryl groups and disulfide bonds. While the contents of the high molecular weight gluten increased with the decrease of low molecular weight protein. Moreover free sulfydryl groups were oxidized to disulfide bonds, which maybe caused by oxidative stress related to ROS. Namely the sulfhydryl groups may be involved in the metabolism of ROS as subunit with reduction. So ROS not only promoted the process of physiological after-ripening, but also had an influence on expression of protein subunits. Thereby affected the process of quality after-ripening.After-ripening was related to the redox state and expression of some proteins, which involved in seed germination, maturation, carbohydrate metabolism, glucose metabolism, protein metabolism and other biological processes. In addition, after-ripening was related to the state and expression of storage proteins. Besides, treatment with 0.2m M MV for 6h could had an influence on the state and expression of some proteins, and made them be close to mature wheat seeds.