The diversity of lectin-detectable sugar residues on root hair tips of selected legumes correlates with the diversity of their host ranges for rhizobia

摘要

Four legumes and two nonlegumes were investigated for the presence of sugars at the tips of their root hairs, using commercially available lectins which have specific affinities for certain sug ars. It was found that while only one lectin (RCA-I, which binds to beta-D-galactose) bound to narrow-host-range legumes and one nonlegume, five out of ten lectins tested bound to the root hair rips of the broad-host-range legume siratro (Macroptilium atropurpureum). None of the lectins rested bound to any part of Arabidopsis roots. Binding of lectins (and therefore the presence of sugars) only at the tips of growing root hairs has led us to deduce that the sugars are the glyco moiety of membrane-bound glycoproteins that are recycled at the base of the tip apical dome, along with excess plasma membrane that is known to be recycled there. As many kinds of signal transduction molecules are membrane-bound glycoproteins, we suggest that these sugars may be involved in early interactions with rhizobia, and that the broad-host-range legume siratro has more kinds of sugars to cope with the wide range of rhizobia it is able to accept for symbiotic interactions. As far as we know, this is the first report of multiple sugars at the same surface area of a tip-growing plant cell. [References: 18]