Effect of Environmental Conditions

Environmental conditions during grain fill alter both wheat yield and flour quality. To elucidate the basis for these changes, comparative proteomics has been used to identify specific protein changes in response to temperature and fertilizer levels during grain fill. Skylas et al. [39] determined the effect of a 3-day high-temperature regimen (40/25°C day/night at 15-17 DPA) on protein profiles in heat-tolerant and heat-sensitive wheat cultivars. At 17 DPA, more proteins responded to high temperature in the endosperm of the heat-tolerant cultivar than to high temperature in the endosperm of the heat-sensitive cultivar. All 17 heat-responsive proteins identified in this study were smHSPs. Because seven proteins responded only in the heat-tolerant cultivar at 17 DPA and one protein remained at high levels at 45 DPA, these proteins were suggested to be candidates for markers for heat-tolerance. Such proteins are of keen interest to plant breeders who are trying to obtain stress-resistant cultivars. In their study, Majoul et al. [40] determined the effect of high temperature (34/10°C day/night) on protein profiles of mature grain. Twenty-five proteins increased in response to high temperature, most of which were thought to function in stress/defense—that is, 70-, 80-, and 83-kD HSPs, chloroplast smHSP, catalase, pectin methylesterase, phosphoinositide-specific PLC, RPM1-like protein, vacuolar ATPase, and LEA protein. The one protein that decreased was glucose-1-phosphate adenyl-transferase, an enzyme functional in starch biosynthesis. In a second study, Majoul et al. [41] determined the effect of high temperature on the accumulation levels of albumins and globulins extracted from mature grain. As found in the previous study, the 16 proteins that increased play a role in stress/defense: HSP 82, smHSPs, vacuolar ATP synthase, JIP, and GTP-binding protein. The eight proteins that decreased included mitochondrial ATP synthase and enzymes functional in metabolism—that is, glucose-1-phosphate adenyltransferase, serine carboxypeptidase, and AdoMet syn-thetase.

DuPont et al. [42] compared the effect of moderate (24/17°C day/night) and high (37/28°C day/night) temperature regimens with or without post-anthesis fertilizer on gluten protein accumulation during grain development. Relative spot volumes of several a-gliadins, «-gliadins, and HMW-GS were lower when grain was produced under the moderate temperature regimen in the absence compared to the presence of post-anthesis fertilizer. In contrast, the relative amount of a major LMW-GS was lower in the presence of post-anthesis fertilizer. Compared to the 24/17° C regimen in the absence of post-anthesis fertilizer, relative amounts of some of the a-gliadins and HMW-GS were higher in grain produced under the high-temperature regimen with or without post-anthesis fertilizer. In contrast, the relative amount of a major LMW-GS decreased under the high-temperature regimen. DuPont et al. [43] also demonstrated that the accumulation rates increased more for the sulfur-poor proteins («-gliadins, HMW-GS) than for the sulfur-rich proteins (a- and y-gliadins, LMW-GS) in grain grown under both temperature regimens in the presence of post-anthesis fertilizer or under the high-temperature regimen alone. Thus, proteomics approaches have led to increased understanding of the specific effects of environmental conditions on gluten and non-gluten proteins during grain development.

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