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International audience; This study provides a detailed characterisation of a leaf protein concentrate (LPC) extracted from Cichorium endivia leaves using a pilot scale process. This concentrate contains 74.1% protein and is mainly composed of Ribulose-1,5-BISphosphate Carboxylase/Oxygenase (RuBisCO). We show that the experimentally determined extinction coefficient (around 5.0 cm−1 g−1 L depending on the pH) and refractive index increment (between 0.27 and 0.39 mL g−1) are higher than the predicted ones (about 1.6 cm−1 g−1 L and 0.19 mL g−1, respectively). In addition, the UV–visible absorption spectra show a maximum at 258 nm. These data suggest the presence of non-protein UV-absorbing species. Chromatographic separation of the concentrate components in denaturing conditions suggests that RuBisCO SC may be covalently bounded to few phenolic compounds. Besides, the solubility of LPC proteins is higher than 90% above pH 6. Such high solubility could make LPC a good candidate as a functional food ingredient.

The NitroSorg project is funded by CASDAR, Ministère de l'Agriculture et de l'Alimentation, France. It involves INRAE and CIRAD through the participation of the AGAP, IATE, BOA research units and the PEAT Experimental Unit, the Eurosorgho and RAGT2n seed companies, and the technical institute ITAVI. Although the SELMET research unit does not benefit directly of financial support of the project, it provides its expertise on feed quality phenotyping tools to the consortium. Nitrosorg will begin in 2022 and will last 42 months. It brings together a multidisciplinary consortium of biologists, geneticists, breeders, biochemists and poultry feed specialists to better understand the establishment of sorghum grain quality for poultry feeding and contribute to the development of breeding tools to optimize breeding efficiency for this target. Indeed, the low digestibility of sorghum grain proteins by gastrointestinal proteases, which has the particularity of decreasing even further after cooking, represents an important obstacle to a wider use of sorghum for feed but also for human nutrition. This low digestibility can be attributed to the interaction of proteins with other grain compounds such as starch or tannins, but is mainly related to the structure and properties of the storage proteins of sorghum grain (kafirins). One of the objectives of this project is to develop high-throughput characterization tools for the protein content and digestibility, but also starch and tannin content and endosperm texture that can affect this digestibility. The consortium will mobilize these tools to characterize the current European varietal offer, a panel representing the worldwide diversity, and the parental lines of the partner's breeding programs. Finally, we will carry, on a smaller panel of genotypes, an analysis of kafirin composition, and an exhaustive analysis of in vitro and in vivo protein digestibility (as part of poultry feeding). These analyses should allow us to assess the relevance of the high-throughput screening tools developed and will lead to the definition of the target ideotypes for poultry feeding. In the long term, these results will contribute to the development of grain sorghum varieties with a better protein content and digestibility, and therefore an improved nutritional value.

International audience; The comprehensive phenolic profile, antioxidant activity and color of sorghum (Sorghum bicolor L., caudatum) grains were investigated in five different stages of growth (from cellular division to maturity). Grains were harvested (2018, Montpellier-France), freeze-dried and cryogenically ground. Colorimetric parameters (L*, a*, b*) were determined and free (FPC) and bound (BPC) phenolic compounds were extracted from wholegrain flours. Antioxidant capacity was determined by DPPH and Folin-Ciocalteu methods in microplates. Phenolic profile was analyzed by UPLC-ESI-QTOF-MSE in negative mode. Data were processed with Progenesis QI using a customized database (PubChem and Phenol explorer) applying: mass error (80%) and reproducibility (3/3). Sorghum grain flours became significantly darker and redness throughout maturation. FPC and BPC ranged from 207.19 to 1052.77 and 268.71 to 624.75 mg GAE/100g (db), respectively; and antioxidant activity between 10.84 to 108.68 and 29.92 to 67.50 mg TE/100g (db). The most immature stage (S1) had the highest FPC content and antioxidant activity in free extracts, while the highest values of BPC were found in mature grains (S4, mature). S2 represents the grain filling stage and showed the same values in both extracts. Globally, 69 FPC and 120 BPC were tentatively identified with 18 compounds present in both extracts. The first stages (S1-S3) showed the highest number and abundance of phenolic compounds. Bound phenolics were the most abundant (72%), mainly in S2, while free soluble phenolics were higher in immature stages, decreasing along grain maturation. PCA allowed a distinguished phenolic profile in each stage, where S1, S2 and mature presented more than 10 unique PC. This work seems to be the first to reveal the phenolic profiling based on metabolomics during sorghum grain growth. These data can be hereafter correlated with proteomic analysis, in order to better understand the digestion problematic involving tannins and kafirins in this cereal matrix.

The Supplementary Material for this article can be found online at: http://journal.frontiersin.org/article/10.3389/fpls.2017.00557/full#supplementary-material; Major nutritional and agronomical issues relating to maize (Zea mays) grains depend on the vitreousness/hardness of its endosperm. To identify the corresponding molecular and cellular mechanisms, most studies have been conducted on opaque/floury mutants, and recently on Quality Protein Maize, are version of an opaque2 mutation by modifier genes. These mutant lines are far from conventional maize crops. Therefore, a dent and a flint inbred line were chosen for analysis of the transcriptome, amino acid, and sugar metabolites of developing central and peripheral endosperm that is, the forth coming floury and vitreous regions of mature seeds, respectively. The results suggested that the formation of endosperm vitreousness is clearly associated with significant differences in the responses of the endosperm to hypoxia and endoplasmic reticulum stress. This occurs through a coordinated regulation of energy metabolism and storage protein (i.e., zein) biosynthesis during the grain-filling period. Indeed, genes involved in the glycolysis and tricarboxylic acid cycle are up-regulated in the periphery, while genes involved in alanine, sorbitol, and fermentative metabolisms are up-regulated in the endosperm center. This spatial metabolic regulation allows the production of ATP needed for the significant zein synthesis that occurs at the endosperm periphery; this finding agrees with the zein-decreasing gradient previously observed from the sub-aleurone layer to the endosperm center. The massive synthesis of proteins transiting through endoplasmic reticulum elicits the unfolded protein responses, as indicated by the splicing of bZip60 transcription factor. This splicing is relatively higher at the center of the endosperm than at its periphery. The biological responses associated with this developmental stress, which control the starch/protein balance, leading ultimately to the formation of the vitreous and floury regions of mature endosperm, are discussed.

International audience; We propose a quantitative approach to probe the spatial heterogeneities of interactions in macromolecular gels, based on a combination of small angle X-ray (SAXS) and neutrons (SANS) scattering. We investigate the structure of model gluten protein gels and show that the gels display radically different SAXS and SANS profiles when the solvent is (at least partially) deuterated. The detailed analysis of the SANS signal as a function of the solvent deuteration demonstrates heterogeneities of sample deuteration at different length scales. The progressive exchange between the protons (H) of the proteins and the deuteriums (D) of the solvent is inhomogeneous and 60 nm large zones that are enriched in H are evidenced. In addition, at low protein concentration, in the sol state, solvent deuteration induces a liquid/liquid phase separation. Complementary biochemical and structure analyses show that the denser protein phase is more protonated and specifically enriched in glutenin, the polymeric fraction of gluten proteins. These findings suggest that the presence of H-rich zones in gluten gels would arise from thepreferential interaction of glutenin polymers through a tight network of non-exchangeable intermolecular hydrogen bonds.

National audience; SANS study of a gluten protein gel: Why are SAXS and SANS profiles diffrents?