Plant Cell Wall Biogenesis During Tip Growth in Root Hair Cells

In plants, cells are surrounded by a rigid cell wall, which restricts changes in cell shape and size; therefore, polarized secretion and deposition of cell wall components take on a particular importance during plant growth and development. In recent years, significant advances have been made in discovering and characterizing enzymes and proteins involved in the synthesis of many of the main cell wall polysaccharides. However, despite these advances little is known of the membrane-trafficking pathways responsible for polarized secretion in plants, and how the specific delivery of cell wall components to regions of cell expansion is controlled. In root hair cells, the majority of new cell wall deposition occurs in a highly polarized manner at the expanding tips of these cells. Additionally, reinforcement of the cell wall and deposition of secondary cell wall components occur selectively in the more distal portions of the root hair cell. In this chapter we will discuss some of the major classes of polysaccharides and structural proteins that are found in plant cell walls and relevant evidence for their selective deposition and function during plant cell wall biogenesis during root hair tip growth.