Partner und Internationale Organisationen
(Englisch)
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A, B, BG, CY, CZ, DK, EE, FIN, F, D, GR, H, IRL, I, LV, LT, NL, N, PL, RO, SK, SI, E, S, CH, GB
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Abstract
(Englisch)
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The suitability of wheat varieties for bread-making depends largely on the prolamins. The amino acid composition of these gluten building-blocks as well as their quantitative regulation have a strong influence on the rheology of the dough and, thus, on the suitability of the variety for bread-making. The wheat/rye 1BL.1RS translocation was reported to reduce drastically rheological properties. However noticeable exceptions exist. This chromosomal rearrangement was designed to transfer resistance to pathogens such as Puccinia recondita, Puccinia gramins, Puccinia striiformis and Erysiphe graminis from rye to wheat. Nowadays this resistance is overcome but 1BL.1RS translocation remains interesting because of the improved yield it produces. To better understand the impact on quality of particular prolamins (Glu-A1 2.., Glu-B3 j and Glu-D3 c) and to gather innovative understandings on prolamin regulation in general. A population of doubled haploid was created by isolated microspore culture. This population was sown in a two years field experiment. The first part of this study reports a new x-type high molecular weight glutenin subunit encoded at the locus Glu-A1 and named 2... The statistical analysis demonstrated that the subunit 2.. was as favorable for quality as the subunit 2*. This is in accordance with the results showing that the 2.. open reading frame had the same number of cysteines as 2*. The small differences in the length of the central domain had no detectable effect on the elasticity, tenacity and baking quality, of the dough. The effects of the rest of the polymorphic loci (Glu-B3 and Glu-D3) also produced innovative results; allele Glu-B3 j, that marks the 1BL.1RS translocation, was found associated with lower dough rheology parameters. It produced lower tenacity, lower extensibility, lower strength and higher softening. Allele Glu-D3 b was also detrimental for rheology when compared to allele c. Its impact was important on dough tenacity and globally it affected quality in a similar extent than the 1BL.1RS translocation. Protein content of the 1BL.1RS lines was significantly higher than that of the regular 1B ones. This induced the production of higher volume bread. In addition, the softening produced by the 1Bl.1RS translocation and Glu-D3 b probably participated also in the higher bread volume by reducing the resistance to deformation of the dough. The comparison of the 2-DE proteomic profiles of sixteen doubled haploid lines, with or without the 1BL.1RS translocation, allowed the assessment of the impact of this 'event' on the prolamins; quantitative and qualitative proteic variations induced by the 1BL.1RS translocation were reported. Eight spots were found only in lines having the 1BL.1RS translocation, 16 other spots disappeared in the same lines. Twelve spots present in both kinds of genotypes met the up- or down-regulated spot criteria. In translocated genotypes, a ?-gliadin having nine cysteine residues was over-expressed by 801 % suggesting that the lack of LMW-GS was counterbalanced by an over-expression of relatively similar prolamins. Identification and quantification of the prolamin fractions on the two dimensional electrophoresis gels demonstrated that the HMW-GS were up-regulated by 25 % in 1BL.1RS DH lines even though the corresponding genes were not located on the missing 1BS chromosome. The ?-gliadins were also up-regulated by 36 %. Moreover, a significantly varying spot, identified as a dimeric alpha-amylase inhibitor, may be considered as a valuable candidate to explain the starch gelatinization defect observed in the 1BL.1RS lines of the DH population. To investigate the impact of the 1BL.1RS translocation on dough strength and to understand how 1BL.1RS genotypes can overcome the loss of Glu-B3 and Gli-B1, the same sixteen DH lines were reclassified into high or low tenacity and into high or low extensibility categories. The results showed that 32 spots, mainly prolamins, were differentially expressed and that five others were specific to high strength DH lines. The polymeric prolamin fractions were also accumulating in high tenacity lines and decreasing in high extensibility lines confirming the role of inter-chain disulfide bound in the resistance to deformation. Oppositely, the monomeric fraction of ?-gliadin and precisely the Gli-A1 allele of parent Toronit favored extensibility and decreased tenacity via higher accumulation (+12 % of ?-gliadins in high extensibility lines) when compared to the Gli-A1 allele of parent 211.12014. The obtained results will help establishing efficient breeding strategies when translocated lines are concerned. Accumulating y-type HMW-GS and good quality ?-gliadin can improve quality. These results will also help reconsidering prolamin variability and prolamin regulation mechanisms. The present study demonstrated also the impact of the 1BL.1RS translocation on starch. This observation can be useful for obtaining 'sprouted-like' wheat cultivars.
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