(1→3)-β-D-Glucan (callose) is a probable intermediate in biosynthesis of cellulose of cotton fibres

Abstract

The biosynthetic pathway of cellulose in higher plants is unknown1. Attempts to produce cellulose in vitro have shown that mainly (1→3)-β-D-glucan (callose) is produced from participate enzyme fractions of higher plants and uridine diphosphate glucose (UDPG)2–5. Some authors have claimed that in certain conditions, (1→4)-β-D-glucosidic linkages were also formed6–10. However, there is no conclusive evidence for the formation of pure (1→4)-β-D-glucans from UDPG. As caUose forms naturally not only in various parts of plants (sieve and pollen tubes, root hairs, cell plates) but also in response to wounding, it seems best to study cellulose biosynthesis in vivo rather than in wounded cells or cell homogenates which might produce callose but not cellulose. Using intact cotton fibres, we have now shown by pulse-chase experiments that callose has a high turnover and is likely to be an intermediate in cellulose biosynthesis at the stage of secondary wall formation.