Mobilisation of storage cell wall polysaccharides in seeds

Plants store carbohydrate polymers in a number of forms. Starch is the prin cipal form, followed by fructans and cell wall storage polysaccharides (CWS P). The latter are present mainly in seeds and consist of magnifications of one of the polysaccharides present in one of the cell wall matrices. CWSPs are classified as mannans, xyloglucans and galactans, the first being subd ivided into pure mannans, galactomannans and glucomannans. The present revi ew updates the principal discoveries concerning occurrence, structure, meta bolism and eco-physiological significance of the seed storage cell wall pol ysaccharides with emphasis on their importance for plant metabolism and ada ptation to their respective environments during evolution. The properties o f CWSPs as storage polysaccharides are compared with starch and fructans an d the current knowledge on the catabolism (including control) of mannan/gal actomannan, xyloglucan, and galactan is reviewed. On the basis of these dat a, the idea that the CWSPs are multifunctional molecules is proposed and th is feature is used as evidence for the hypothesis that, during evolution, t he CWSPs were involved in cycles of transference of functions which led the m to become storage polysaccharides, yet preserving some of their previous primary cell wall functions. (C) 2000 Editions scientifiques et medicales E lsevier SAS.