Plant cell wall polysaccharides: Structure and biosynthesis

Abstract

Plant cells are surrounded by cell walls consisting of complex networks of polysaccharides and glycoproteins. Cell walls play a vital role in a plants development and its interactions with the environment. The biosynthesis of cell walls is fueled by carbon fixed by solar energy during photosynthesis. The amount of carbon fixed annually is estimated to ˜2 × 10 11 tonnes (Hall. Solar energy use through biology — past, present and future. Sol Energy 22:307—328, 1979). Thus, plant cell walls represent a valuable sustainable carbon source for human activities. Plants use complex mechanisms that require the coordinated action of hundreds of glycosyltransferases and other enzymes involved in sugar substrate interconversion to build cell wall polysaccharides. This chapter will focus on discussing current advances in the biosynthesis and structures of these wall polysaccharides, including cellulose, a variety of hemicellulosic polymers, pectins, and structural hydroxyproline-rich glycoproteins (extensins and arabinogalactan-proteins). These polymers are organized into complex but dynamic networks that are still the subject of extensive research. Much work is still needed to determine the functions of many glycosyltransferases involved in building these polymers. In addition, how plant cells manage to secrete and organize them into such complex networks remains a mystery. Thus, the future holds exciting discoveries in the field of plant cell wall polysaccharide biosynthesis.