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IX Improvement of Grain Quality

Coping with Wheat Quality in a Changing Environment: Proteomics Evidence for Stress Caused by Environmental Changes

Abstract High temperatures (HTs) during grain filling adversely impact grain yield and its end-use quality for wheat. HTs strongly reduce the expression of major enzymes associated with starch synthesis, whereas enzymes associated with defence against stress and protein folding are dramatically increased. Using proteomics tools, the effect of different temperature regimes on storage protein (SP) accumulation was investigated. HT significantly decreased the quantity per grain of individual gliadin and glutenin spots, but at maturity the ratio of gliadin to glutenin was not modified. HT during grain filling strongly reduced starch accumulation, modified the size distribution of starch granules, and to a much lesser extent, reduced the quantity of total proteins per grain. The aggregation and polymerisation of SP was investigated using asymmetric flow field flow fractionation. Previous analyses of near-isogenic hard/soft lines showed that characteristics of glutenin polymers were significantly influenced by puroindoline alleles (Pina-D1a and -D1b), and proteomics analysis showed that a typical mechanism of unfolded protein response occurs in ER, resulting from stress during protein accumulation. Effects of alleles encoding puroindolines, HMW-GS and LMW-GS, and temperature during grain development on glutenin polymer characteristics, dough rheological properties, and bread loaf volume were investigated for 40 cultivars grown in six environments in France. A difference of only 2 °C in average daily air temperature between locations during the grain-filling period resulted in increased molecular mass of the glutenin polymers and dough tenacity, but decreased dough extensibility and bread loaf volume. To compensate these adverse effects, some solutions are suggested.

Keywords Dough properties • Endosperm • Gliadins • Glutenins • Glutenin polymers • Heat stress • Proteomics • Starch • Temperature

High Temperature Is a Major Factor Affecting Wheat Production

Cereals and particularly winter crops are influenced by ongoing climate changes. Drought may strongly affect plant physiological development resulting in fewer fertile ears per plant and fewer grains per spike. Among abiotic stresses, heat stress, particularly during grain filling, is the main factor responsible for a reduction in grain weight, and hence in yield (Jenner 1994; Ottman et al. 2012). High temperatures when storage compounds are accumulating in the grain are one of the main factors influencing wheat end-use value (Wardlaw and Wrigley 1994). Although a gradual rise in daily maximum temperatures causes less damage to grain compounds than a sudden temperature rise during grain filling, wheat cultivars may also respond differently to high temperatures (Stone and Nicholas 1994; Stone et al. 1997). Whatever the cultivar studied, high temperatures have been shown to shorten the effective grain filling period, and may significantly increase protein concentration because of more dramatic effect on starch than on protein accumulation (Altenbach et al. 2003; Blumenthal et al. 1991a, b, 1995; Corbellini et al. 1998; Triboï et al. 2003). Many studies have addressed the responses of wheat grain to high temperatures during grain filling using either transcriptomics tools (Altenbach and Kothari 2004; Altenbach et al. 2007; Hurkman et al. 2003; Perrotta et al. 1998) or proteomics approaches (Hurkman et al. 2009; Laino et al. 2010; Majoul et al. 2003, 2004; Majoul-Haddad et al. 2013; Skylas et al. 2002; Vensel et al. 2005). In the present study, major events occurring in the wheat endosperm in response to high temperatures during grain filling were investigated using proteomics approaches.

The present report describes major variations in individual storage proteins (SP), metabolic enzymes and proteins involved in carbohydrate metabolism and glutenin polymer formation in response to HT, based on three experiments carried out under controlled conditions and one multi-location field trial in France.

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