The Biosynthesis and Function of Polysaccharide Components of the Plant Cell Wall

Abstract

The cell wall of land plants consists of three layers, namely the middle lamella, the primary cell wall, and the secondary cell wall. The middle lamella is directly derived from the cell plate generated during cytokinesis and the primary cell wall is deposited onto the middle lamella during the cell expansion process. The two cell wall layers are generally found in all cell types, whereas the secondary wall is deposited onto the primary cell wall in certain specific cell types after cell expansion has ceased (Albersheim et al., 2011; Fig. 1.1). The three layers differ from each other in terms of their chemical nature and physical properties, and they serve different biological functions. Although both the primary and secondary cell walls directly function as a mechanical housing capable of resisting both turgor pressure from the inside out and compression force from the outside in, only the primary cell wall can extend or deform in response to the force applied and thereby determine the direction and rate of cell expansion (Burgert and Frantzl, 2007; Wasterneys and Collings, 2007; Fig. 1.1). In addition to these mechanical roles, the primary cell wall functions as an information processing system. Typical functions include non-cell-autonomous regulation of cell differentiation via apoplastic signaling (Irving and Gehring, 2012; Wolf et al., 2012a), particularly in meristems, defensive responses to pathogens and parasites (Bradley et al., 1992; Vorwerk et al., 2004), and interactions with symbionts. The dynamics of the primary cell wall therefore play a pivotal role in determining cell shape and function during development and in response to environmental stimuli. Accordingly, in this chapter we will focus on the primary cell wall and the dynamic aspects of its major components, namely cellulose and matrix polysaccharides, in relation to its function.