Search

Reserve starch, the major component of wheat kernel, consists of amylose and amylopectin. The variation of their ratio (about 1:3 in normal wheat) has a potential impact on nutritional and technological characteristics of wheat-derived foods. Previously, mutations in homeologs of three key genes involved in starch biosynthesis (granule-bound starch synthase I, GBSSI; starch syntase IIa, SSIIa; a-glucan-branching, SBEIIa) have been identified and pyramided obtaining three complete null bread wheat lines, respectively named Cad-GBSSI*, Cad-SSIIa* and Cad-SBEIIa*. These genotypes have altered amylose/amylopectin ratios, starch properties, and polysaccharide compositions. In order to refine the characterisation of starch metabolism and to bring out transcriptional divergences underlying pleiotropic effects, the grain transcriptomes of Cad-GBSSI*, Cad-SSIa* and Cad-SBEIIa* mutants were compared to the wild-type at 15 and 25 days post anthesis (dpa). First, the principal component analysis of RNA-seq data scored similar gene expression between replicates and biological variability of the mutants. At 15 dpa, Cad-GBSSI*, Cad-SSIIa* and Cad-SBEIIa* diverged for 1114, 1737 and 335 genes compared to controls, suggesting a stronger and precocious effect of the SSIIa loss of function. The transcriptome of all mutants encompassed over 3000 DEGs at 25 dpa, suggesting a later responsive boost. As for the starch pathway, DEG profiles were consistent with the patterns of over 30 key genes that were targeted in a previous work. DEG analyses also pointed to gene sets that were modified recurrently or specifically in the mutants. The commonly altered genes included ca. 60 sequences related to carbohydrate pathways, while 658, 420 and 1282 were respectively peculiar for the Cad-GBSSI*, Cad-SSIIa* and Cad-SBEIIa* genotypes. Moreover, these mutants shared common enriched GO-terms involved in nitrogen, glutamate/glutamine metabolism and proteolysis processes that further supported the alteration of C/N equilibria. Interestingly, GO-term analysis also pointed at some collateral effects that recurred in the three mutants and regarded the functioning of both chloroplast and photosystems, suggesting some interference with photosynthesis, a well-known process in immature seeds.

Resistant starch (RS) in foods has positive benefits for potentially alleviating lifestyle diseases. RS is correlated positively with starch amylose content. This study aimed to see what level of amylose in durum wheat is needed to lower pasta GI. The silencing of starch synthases IIa (SSIIa) and starch branching enzymes IIa (SBEIIa), key genes involved in starch biosynthesis, in durum wheat cultivar Svevo was performed and spaghetti was prepared and evaluated. The SSIIa and SBEIIa mutants have a 28% and 74% increase in amylose and a 2.8- and 35-fold increase in RS, respectively. Cooked pasta was softer, with higher cooking loss but lower stickiness compared to Svevo spaghetti, and with acceptable appearance and colour. In vitro starch digestion extent (area under the digestion curve) was decreased in both mutants, but much more in SBEIIa, while in vivo GI was only significantly reduced from 50 to 38 in SBEIIa. This is the first study of the glycaemic response of spaghetti prepared from SBEIIa and SSIIa durum wheat mutants. Overall pasta quality was acceptable in both mutants but the SBEIIa mutation provides a clear glycaemic benefit and would be much more appealing than wholemeal spaghetti. We suggest a minimum RS content in spaghetti of ~7% is needed to lower GI which corresponded to an amylose content of ~58%.

Water deficit and high temperatures are the main environmental factors which a ect both wheat yield and technological quality in the Mediterranean climate. The aim of the study was to evaluate the variation in the gluten protein assembly of four durum wheat genotypes in relation to growing seasons and di erent nitrogen levels. The genotypes, Marco Aurelio, Quadrato, Pietrafitta and Redidenari, were grown under three nitrogen levels (36, 90 and 120 kg ha􀀀1) during two growing seasons in Southern Italy. Significant lower yield and a higher protein concentration were observed in the year characterized by a higher temperature at the end of the crop cycle. The e ect of the high temperatures on protein assembly was di erent for the genotypes in relation to their earliness. Based on PCA, in the warmer year, only the medium-early genotype Quadrato showed positive values along the “protein polymerization degree” factor, while the medium and medium-late genotypes, Marco Aurelio and Pietrafitta showed negative values along the “proteins assembly” factor. No clear separation along the two factors was observed for the early genotype Redidenari. The variation in gluten protein assembly observed in the four genotypes in relation to the growing season might help breeding programs to select genotypes suitable for facing the ongoing climate changes in Mediterranean area.

The main goal of the project was to develop online corrosion sensors in pulverised (PF) and circulating fluidised bed (CFB) combustion systems in order to fire biomass and other low-grade fuels safely at high portions in power plants. Another important goal was to find protective effects from coal in power plant furnaces during co-firing biomass and other low-grade fuels. The obtained results helped significantly to understand the information derived from corrosion sensors, which is essential to their integration for power plant process control. The studied sensors already in their present form have potential for power plant control. Due to the complicated character of signal formation and some needs to change particular details in the sensor construction, further development work would be useful. Optimising the sensitivity and availability to long-lasting reliable operation in very difficult environments would be key issues. The project results can also be utilised to re-consider the role of coal in energy production. The new idea to use coal as a protective agent ensuring biomass firing at very high portions instead of considering coal only as a co-firing fuel, can improve acceptance and public opinion to the use of coal in biomass power plants. The addition of coal in many biomass power plants has been forbidden so far due to fossil CO2 formation, which can prevent the utilisation of many potential biomass fuels in those plants. Experimental work was first conducted with pilot-scale pulverised fuel and circulating fluidised bed reactors with various sizes. The obtained results, refined further with modelling tools, were successfully used to conduct the power plant tests.

Wheat (Triticum aestivum) grains contain large protein polymers constituted by two main classes of polypeptides: the highmolecular- weight glutenin subunits and the low-molecular-weight glutenin subunits (LMW-GS). These polymers are among the largest protein molecules known in nature and are the main determinants of the superior technological properties of wheat flours. However, little is known about the mechanisms controlling the assembly of the different subunits and the way they are arranged in the final polymer. Here, we have addressed these issues by analyzing the formation of interchain disulfide bonds between identical and different LMW-GS and by studying the assembly of mutants lacking individual intrachain disulfides. Our results indicate that individual cysteine residues that remain available for disulfide bond formation in the folded monomer can form interchain disulfide bonds with a variety of different cysteine residues present in a companion subunit. These results imply that the coordinated expression of many different LMW-GS in wheat endosperm cells can potentially lead to the formation of a large set of distinct polymeric structures, in which subunits can be arranged in different configurations. In addition, we show that not all intrachain disulfide bonds are necessary for the generation of an assembly-competent structure and that the retention of a LMW-GS in the early secretory pathway is not dependent on polymer formation. L'articolo è disponibile sul sito dell'editore: http://www.aspb.org