The synthesis of xyloglucan, an abundant plant cell wall polysaccharide, requires CSLC function

Significance Plant cells have a polysaccharide-based wall that maintains their structural and functional integrity and determines their shape. Reorganization of wall components is required to allow growth and differentiation. One matrix polysaccharide that is postulated to play an important role in this reorganization is xyloglucan (XyG). While the structure of XyG is well understood, its biosynthesis is not. Through genetic studies with Arabidopsis CSLC genes, we demonstrate that they are responsible for the synthesis of the XyG glucan backbone. A quintuple cslc mutant is able to grow and develop normally but lacks detectable XyG. These results raise important questions regarding cell wall structure and its reorganization during growth. The series of cslc mutants will be valuable tools for investigating these questions.