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On the slime trail
The rhizosphere is a zone of extensive interchange of biomolecules between organisms: cell-to-cell signalling, organism-to-organism signalling, interchange of nutrients, secretion of inhibitors and allelo-chemicals, and so on. One player often overlooked in all this is the mucilage of plant roots, which, in addition to its lubricating and protective role for the root, may also act as local soil conditioner and provide nutrients for micro-organisms. These nutrients are derived from breakdown of the mucilage polymers and are thus rich in particular monosaccharide units, one of which is L-fucose (2-deoxy-L-galactose). Classic studies in the 1960s and 1970s, using radioactive precursors, established the role of the Golgi in the synthesis of mucilage and of cell wall polysaccharides. More recently, indirect immuno-analysis has been used to study the synthesis, transport and subsequent metabolism of these polysaccharides. In this technique, the specific sugar-binding properties of lectins are used to recognize particular sugars and those lectins are recognized by specific antibodies. However, Sinha Roy et al. (University of Delhi, pp. 293-299) have now developed a more direct route for studying the monosaccharide units that constitute mucilage and similar polymers. Fucose was ligated to bovine serum albumin and antibodies were raised against the conjugate. The antibodies show a high degree of specificity toward fucose and, in detection systems with gold- or peroxidase-linked secondary antibodies, can be used to obtain a detailed picture of the distribution of fucose (and hence mucilage polysaccharides) in the root cap. This opens the way for immuno-microscopy of mucilage synthesis and distribution. It will thus be a very useful new tool in, for example, investigations of the effects of changing environmental conditions on the metabolism of mucilage and other polysaccharides. The root and its environment are often overlooked - out of sight, out of mind - and studies such as these are thus very welcome.
Professor J. A. Bryant
University of Exeter, UK
j.a.bryant{at}exeter.ac.uk
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