Submitted to: Proteome Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 22, 2013
Publication Date: February 22, 2013
Citation: Hurkman II, W.J., Tanaka, C.K., Vensel, W.H., Thilmony, R.L., Altenbach, S.B. 2013. Comparative proteomic analysis of the effect of temperature and fertilizer on gliadin and glutenin accumulation in the developing endosperm and flour from Triticum aestivum L. cv. Butte 86. Proteome Science. doi:10.1186/1477-5956-11-8. Interpretive Summary: Wheat flour is used worldwide as an ingredient in a variety of baked products due to its unique protein properties. When flour is mixed with water, the proteins interact to form gluten, a continuous protein network that is responsible for the viscoelastic properties and gas holding capacity of flour dough. Gluten is a complex mixture of proteins made up of five protein classes: high molecular weight glutenin subunits (HMW-GS), low molecular weight glutenin subunits (LMW-SG), and the alpha, gamma, and omega gliadins. Variations in flour quality are related to effects of environmental conditions on gliadin and glutenin composition. Since consistent flour quality is important to end users, an increased understanding of the effects of environment on individual gliadins and glutenins and their relationship to quality is needed. In this study, the effect of fertilizer and high temperature on the gliadins and glutenins was compared during grain development and in flour from the mature grain using quantitative two dimensional gel electrophoreis. Gluten protein responses were remarkably similar for fertilizer and temperature, even though high temperature shortened the grain filling stage and decreased grain size. The proportions of HMW-GS, a-gliadins, and '-gliadins increased and those of the LMW-GS decreased. In addition, the ratios of HMW-GS to LMW-GS and of gliadins to glutenins, which are related to bread quality, increased in response to fertilizer or high temperature. This study provides clues about the regulation of specific flour protein genes to environmental cue and is an important step in identifying targets for breeding programs aimed at improving flour quality.
Technical Abstract: Background: Increases in fertilizer or temperature during grain fill modify protein composition of the wheat grain and alter flour quality. Flour quality is largely determined by the gluten proteins, a complex mixture of proteins consisting of high molecular weight-glutenin subunits (HMW-GS), low molecular weight-glutenin subunits (LMW-GS), and a-, '-, and '-gliadins. Detailed proteomic analyses of the effects of fertilizer and high temperature on individual gliadin and glutenin protein levels are needed to determine how these environmental factors influence flour quality. Results: Wheat plants (Triticum aestivum L. cv. Butte 86) were grown with and without fertilizer or high temperature. Quantitative two-dimensional gel electrophoresis was used to analyze gluten protein composition in the endosperm during grain development and in flour milled from mature grain. High temperature decreased the duration of grain fill, reduced grain size, and increased gluten protein amount per grain. The temporal pattern of gluten protein accumulation during development was similar for grain produced under a 24/17oC regimen with or without fertilizer. This temporal pattern was maintained, but compressed, for a 37/28oC regimen with or without fertilizer. Gluten protein responses to fertilizer or high temperature were similar during late developmental stages and in flour. The proportions of HMW-GS, a-gliadins, and '-gliadins increased and those of the LMW-GS decreased. In addition, the ratios of HMW-GS to LMW-GS and of gliadins to glutenins increased similarly in response to fertilizer or high temperature. Conclusions: Gluten protein responses were remarkably similar for fertilizer and temperature and were not additive when these treatments were combined. The temporal patterns of gliadin and glutenin accumulation during development and the proportions of these proteins in flour were comparable for fertilizer and high temperature. These results indicate that the developmental program for the sequential accumulation of gluten proteins in the endosperm is maintained despite the shortened duration of grain fill imposed by high temperature. The responses to high temperature can be explained by source-sink activities in the wheat plant and highlight the importance of considering nutritional status when assessing environmental effects on the gluten proteins.