The cell wall

We are monitoring the composition and distribution of parietal polymers mainly using biochemical and imaging approaches. In this way, we have helped to highlight the great variability of walls, particularly in the different tissues of developing cereal grains (Chateigner-Boutin et al., 2018  ; Francin-Allami et al., 2019),  in cereal stems and in fleshy fruits (Dheilly et al., 2016 ; Guillon et al., 2017 ). Our work has also focused on mucilage, a substance released by Arabidopsis seeds at the time of imbibition and which is considered to be a simplified model for the study of pectin biosynthesis and their interactions with other polysaccharides (North et al., 2014). At present and in the coming years, these characterisations will continue, in particular with the study of the deconstruction of grain walls during the germination process, and with the study of modifications to the walls induced by variations in growing conditions, in particular the effects of global warming.

In recent years, we have identified a number of players involved in the mechanisms of wall construction by analysing collections of lines or using subcellular proteomics and transcriptomics approaches (Chateigner-Boutin et al., 2015; Chateigner-Boutin et al., 2016; Cherkaoui et al. 2018). The functional exploration of some of these target genes/proteins is carried out using two approaches: in vitro by testing the enzymatic activity of proteins produced in heterologous systems; in vivo by modifying the expression or sequence of the corresponding genes.In cereals we have identified enzymes for the biosynthesis, assembly, remodelling and degradation of cereal grain and stem wall polymers (arabinoxylans, mixed β-glucans, pectins, mannans, lignins). For example, we have identified a xyloglucan-endotransglycosylase/hydrolase (XTH) whose expression is surprisingly high in the grains of certain Poaceae: the enzymatic activity of these XTHs is currently being investigated in order to determine their role in the remodelling of parietal polysaccharides during grain development. The role of peroxidases and laccases in the lignification of Poaceae walls is also being investigated (Le Bris et a l., 2019)

The team's work has also contributed to the identification of biosynthesis enzymes and assembly mechanisms for Arabidopsis mucilage polysaccharides (Saez-Aguayo et al., 2021; Ralet et al., 2016). The dynamics of macromolecule assemblies in plant tissue walls contribute to the variability of their structural and functional properties. We are interested, for example, in the spatio-temporal variability of the properties of developing wheat grain walls. These variabilities in the elasticity or rigidity properties of the walls could lead to differences in growth between regions of the grain and contribute to determining the size and characteristic shape of the grain (Thang Duong Quoc Le 2020 thesis). In addition, parietal compounds and their variability could contribute to the regulation of tissue hydration properties during seed maturation and germination (Chateigner-Boutin et al., 2021 ; Fanuel et al., 2018).