Implications of the Existence of a Glycomic Code in Plant Cell Walls for Plant Biology and Biotechnology

Abstract

Polysaccharides found in plant cell walls display a code that is produced as a result of polysaccharide branching and from fine adjustments of the biosynthetic machinery within plant cells. This code, here called “glycomic code”, confers chemical diversity to cell wall structure, this being one of the features responsible for differences among cells and tissues. The glycomic code generates semantics through the formation of composites (combination of different polymers) that display different chemical and physical properties. This generates multiple functions within the cell walls each with its respective function and biological meaning. For instance, the assembly of polymers will determine cell form as well as emergent properties of tissues and organs of the plant. The glycomic code regulates the resistance to hydrolysis so that in order to disassemble the cell wall of a plant, a given organism (including microorganisms, herbivores and the plants themselves) has to posses a decoding (or decrypting) key. Whereas some fruits can “relax” the glycome code and allow organisms to have access to the interior of cells so that this service will be exchanged by seed dispersion, other tissues can lock the glycomic code (the xylem in the vascular systems for ex.) so that microorganisms would seldom gain access to the sugars in the cell walls. Essentially, as the cell walls are an important barrier between the cytoplasm of plant cells and the exterior, the existence of the glycomic code is likely to be one of the reasons why plants can exist as stable organisms in Nature. Here I present evidence that the fine structure of all classes of hemicelluloses known display fine structural variability consistent with the existence of the glycomic code. On this basis, I present evidences from literature on how the glycomic code is used to give rise to biological meaning for several phenomena in plant biology. Finally, I will present some ideas on how the understanding of the glycomic code and its semantic implications can be used in plant biotechnology.