| Millet was artificially domesticated from Setaria viridis,and its scientific name is“Setaria italica(L.) Beau”. Millet is an ancient crop originated in China for thousands of years,has been the main cultivated crops in northern China, known as the Chinese nation nurtured crop.due to the rapid development of the wheat, corn level of scientific research, farmland irrigation conditions improve, making the high-yield crops such as corn and wheat acreage is increasing rapidly, millet gradually withdraw from the major grain-producing crops, acreage significantly reducing. But millet is rich in nutrition, which provide energy, dietary fiber,protein, minerals and vitamins required for human health. Besides, millet plays an increasingly important role in the development of sustainable agriculture and crop genetic breeding theory research. Therefore, investigating the varieties of different physical and chemical features of millet grains protein component and the mechanism of millet t response to drought stress has certain guiding significance ans may lay the theoretical foundation in industrial application.This study employed 10 types of millet as materials, linking field experiments and laboratory analysis to investigate the physicachemical properties of millet grains, and in the study the millet grains are cultured and treated with drought stress, which is no irrigation during its growth period, while the control groups were cultured in the same growth conditions. The analysis of proteomics changes in the grains were conducted. The MALDI-TOF-TOF analysis were applied to identify the differential expressed proteins(DEPs), the molcular function, biological and metabolic process of the DEPs involved in drought were also analyzed as well. The main conclusions are as follows:(1) Physicochemical and functional properties of different kinds of millet grain proteins(MGP) were studied. Content of protein was different in different kinds of millet grain, for7.77%-12.32%, Gigu 6(G6) got the best value,while Huangjinmiao(G8) got the worst.Solubility markedly decreases near the isoelectric point, generally between pH 4.2~4.6 forMGP. Different varieties of millet grain protein has different components, from high to low were prolamin, albumin,SDS-protein, glutelin,2ME-protein and globulin, and their isoelectric points were 5.4,3.8,5.6,4.4, 5.0 and 3.6. The amino acid content in different varieties were similar, and glutamic acid got the most, cystine, methionine and histidine were the limiting amino acid in millet grain. The SDS-PAGE pattern suggested there were many bands in MGP,for albumin, the bands were mainly focused on the molecular weight of 35.2 and 22.7 kDa,and globulin were focused on the molecular weight of 11.0 kDa.(2) There are certain differences in MGP functional properties. The solubility of MGP is highest at low acidic and high alkaline pH values. Under conditions of alkaline or acid, G4 and G7 had a worse performances than other kinds of MGP. G8 got a better emulsification and emulsion stability than other cultivars. In different kinds of MGP, G7 and G10 had a worse foaming and foaming stability than others. For water absorption capacity(WAC),millet grain was around 6.0 g/g, and G9 was higher than others. And for oil absorption capacity,MGP had a value of 6.9 g/g, and G2 got the best. G4 and G10 had higher minimum gel concentration than others.(3)All the DEPs above were analyzed by MALDI-TOF-TOF. Totally, 104 in the millet grain were successfully identified.They could be classified into 13 function groups, such as TCA cycle, protein metabolism, detoxification and defense. We also analyzed the sub-cellular localization of these DEPs, and the results showed that most of the DEPs in grain were localized in cytoplasm(47.62%) and liquid(19.05%). Molecular function and Metabolic pathways analysis results showed that The glycolytic pathway were inhibited under drought stress, while tricarboxylic acid cycle(TCA) pathway were enhanced.The amino acid and protein metabolism were enhanced in grains. Consequently resulted in the complicated change of energy metabolism, and a new homeostasis was established. |
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