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Vegetable proteins: a major issue for food and health

About 80% of the world's wheat production is used after industrial processing. Most of these transformations require a high protein concentration that can be compensated by a specific protein composition adapted to the different uses. The storage proteins, glutenins and gliadins, make up about 80% of the total proteins in the grain. They agglomerate during the hydration and kneading of the flour and form the gluten network. Environmental conditions can affect the different stages of maturation of these storage proteins.

If gluten gives the dough its visco-elastic properties, it can lead to health problems (celiac disease, allergies or hypersensitivity). Wheat is a basic element of the human diet, and its proteins cover nearly 20% of our needs. We are now approaching a transition towards a sustainable diet where the proportion of vegetable proteins consumed has to be increased to the detriment of animal proteins. Wheat proteins are therefore important for technological quality and health. Consequently, their concentration, composition and maturation are an essential object of research.

In this context, it is necessary to finely analyze the properties of the grain in order to respond jointly to technological (processor expectations) and health (consumer expectations) issues, knowing that protein concentration is negatively correlated to grain yield but that there is genetic variability for the deviation from this relationship as there is also genetic variability in composition. Finally, better quality must be achieved by reducing the environmental and health impact of crops and considering the components of climate change. Alongside agronomic solutions, linked in particular to cropping practices, plant improvement can offer solutions by breeding varieties with a higher protein concentration and/or an adapted composition and showing a high stability for these characteristics.

In this context, the challenge of the team's project is to develop knowledge and tools to facilitate the selection of bread wheat varieties that meet quality criteria and are adapted to new production contexts by identifying (1) phenotypic traits and their genetic variability, and (2) molecular markers and genes linked to these traits or their components.

A strategy at different scales to control the quality of proteins in grain

Within this framework, the priority research questions that are developed concern the genetic determinism and the study of molecular mechanisms that, in interaction with the abiotic environment, control (1) the concentration, (2) the composition and (3) the maturation of proteins in bread wheat grain.

The research strategy has three main stages. (1) Global approaches for screening genetic collections in order to quantify the variability and identify diversified behaviours in interaction with the most determining variations in the environment (nitrogen and sulphur nutrients, thermal and hydric constraints), and in the genetic background (contrasting lines). (2) Candidate genes are identified using quantitative genetic approaches (association genetics), network constructs combining information at several scales (proteome, transcriptome) and molecular screens (double-hybrid, blue native page). (3) Candidates from these approaches are functionally validated using variants (transgenics, TILLING, NILs) and molecular and cellular analyses to understand the mechanisms underlying the observed phenotypes. Depending on the targets, research actions are placed at different stages of this strategy. This global approach allows the identification of agronomic traits and the molecular markers associated with them.

In this context, the activities of the QualiGrain team are declined according to three axes of research:

Axis 1 - Increasing protein concentration and nutritional value

Axis 2 - Controling the protein composition to adapt it to the uses

Axis 3 - Exploring the UPR pathway in relation to protein maturation

The team relies mainly on projects funded by the French National Research Agency (ANR), the French Fund to Support Plant Breeding (FSOV), France Agrimer and the European Union : Research projects.