The wheat grain is an important source of food, animal feed and industrial raw material. The grain starchy endosperm is a storage tissue that corresponds approximately to the wheat flour. Cell walls only account for about 3% of the endosperm weight but they are prominent for wheat end-use quality (milling, bread-making) and as dietary fibre, they have a major impact on nutritional quality. The cell wall polysaccharides in the wheat endosperm consist in 70 % feruloylated arabinoxylans (AX) and 20% mixed-linked beta-glucans (MLG) which are deposited in the walls during the grain development. Early works have shown that in addition to these major polysaccharides, cellulose and mannans are also found in minor amounts in the dry grain endosperm. More recently callose and xyloglucans were detected transiently in the developing endosperm. No pectins were ever detected although pectins accumulate in the endosperm of the closely related Brachypodium distachyon. By proteomic analysis of Golgi-enriched fractions obtained from the endosperm of developing wheat we identified glycosyltransferases (GT) belonging to families implicated in the synthesis of xylans, MLG, mannans, xyloglucans and pectins. We therefore decided to further analyse the cell wall composition in the endosperm. Positive signals were obtained for mannans, xyloglucans and several pectin domains (homogalacturonans, rhamnogalacturonans, galactans and arabinans) using specific antibodies and after removing the major polysaccharides. Interestingly, some of the minor polysaccharides accumulate evenly in the whole endosperm while others specifically in specialized cells. The transfer cells in the crease region appeared strongly labelled for galactans, arabinans and xyloglucans. The endosperm cell wall is therefore more complex than once thought. We are generating transgenic wheat to silence several genes potentially involved in the synthesis of these polymers to evaluate their role in the developing grain.