Plant Physiol, July 2002, Vol. 129, pp. 1054-1065

The Liverwort Contains a Lectin That Is Structurally and Evolutionary Related to the Monocot Mannose-Binding Lectins¹

Laboratory for Phytopathology and Plant Protection (W.J.P., E.J.M.V.D.), and Rega Institute, Laboratory of Molecular Immunology (P.P.), Katholieke Universiteit Leuven, 3001 Leuven, Belgium; and Institut de Pharmacologie et Biologie Structurale, Unité Mixte de Recherche-Centre National de la Recherche Scientifique 5089, 31077 Toulouse cedex, France (A.B., J.B., P.R.)

A mannose (Man)-binding lectin has been isolated and characterized from the thallus of the liverwort Marchantia polymorpha. N-terminal sequencing indicated that the M. polymorpha agglutinin (Marpola) shares sequence similarity with the superfamily of monocot Man-binding lectins. Searches in the databases yielded expressed sequence tags encoding Marpola. Sequence analysis, molecular modeling, and docking experiments revealed striking structural similarities between Marpola and the monocot Man-binding lectins. Activity and specificity studies further indicated that Marpola is a much stronger agglutinin than the Galanthus nivalis agglutinin and exhibits a preference for methylated Man and glucose, which is unprecedented within the family of monocot Man-binding lectins. The discovery of Marpola allows us, for the first time, to corroborate the evolutionary relationship between a lectin from a lower plant and a well-established lectin family from flowering plants. In addition, the identification of Marpola sheds a new light on the molecular evolution of the superfamily of monocot Man-binding lectins. Beside evolutionary considerations, the occurrence of a G. nivalis agglutinin homolog in a lower plant necessitates the rethinking of the physiological role of the whole family of monocot Man-binding lectins.