Annals of Botany

In the frame of the rose

Technical innovation and advances in knowledge are tightly linked. The desire for knowledge drives the development of techniques; better techniques then give us more detailed knowledge. A particularly good example of this is analytical biochemistry, covering the whole gamut of compounds and complexes synthesized by living organisms. Research on the angiosperm cell wall illustrates this very well. Knowledge of the polymers involved in the wall and of their interlinkages has expanded enormously since the early 1970s and continues to do so. One of the features of the general model for angiosperm cell walls proposed by Albersheim’s group in 1973 was the existence of covalent linkages between the hemicellulose and the acidic pectin components of the wall. Over the succeeding years, the existence and nature of those linkages has been gradually clarified. This is clearly seen in the work of Stephen Fry’s group at Edinburgh, UK, exemplified here in this paper with Zoë Popper (pp. 91–99). The group had previously obtained evidence for the existence in Rosa suspension cultures of a covalently linked complex of xyloglucan and pectin. In the work presented in this paper, they labelled xyloglucans by feeding the cells with [³H]arabinose and then subjected the cell walls to a range of fractionation and analytical techniques. The results are very clear: in Rosa, 60 % of the labelled xyloglucan is found in covalent linkage with the acidic pectin fraction made up of rhamnogalacturonan. Further, this type of linkage is not confined to rose. In a range of angiosperms, including two monocots, between 44 and 70 % of the xyloglucan is linked with acidic pectin. In Arabidopsis further evidence for such linkages was obtained by the demonstration that 20 % of the [¹⁴C]galacturonate-labelled pectins (obtained by feeding cells with [¹⁴C]glucuronic acid) are linked with xyloglucan. The authors conclude that such evolutionarily conserved linkages are likely to be essential for cell wall structure and function.

Professor J. A. Bryant
University of Exeter, UK
j.a.bryant{at}exeter.ac.uk