163 1 Introduction During the long course of interaction and co-evolution with herbivorous insects, plants have evolved a broad range of defense mechanisms to counteract insect attack (Chen 2008). Next to the presence of structural defense barriers, plants have devel- oped several chemical defense strategies towards herbivorous insects. These defense chemicals include plant secondary metabolites and proteins that can reduce the nutri- ent value of the plant material or have a direct effect by interfering with the normal insect metabolism. One particular class of these defense proteins is plant lectins, a heterogeneous group of proteins that specifically interact with sugars (Peumans and Van Damme 1995; Czapla 1997; Van Damme et al. 2007, 2008). Many plants includ- ing different food crops such as wheat, rice, potato, tomato, soybean and bean contain lectins (Van Damme et al. 1998). Nowadays, the term plant lectin is used for all plant proteins possessing at least one non-catalytic domain, which binds reversibly to a specific mono- or oligosaccharide (Peumans and Van Damme 1995). Lectins from different plant species often differ with respect to their molecular structure and speci- ficity. Based on sequence similarity, plant lectins can be divided in different sub- groups of structurally and evolutionary related proteins (Table 1). Each member of a lectin family shares one or more carbohydrate-binding domains with all other members. The major plant lectin families are: (1) amaran- thins, (2) lectins with a Nictaba domain, (3) chitin-binding lectins composed of hevein domains, (4) the GNA-related lectins, (5) the jacalin-related lectins, (6) the legume lectins and (7) lectins with ricin-B domains (Van Damme et al. 2007). The G. Vandenborre and G. Smagghe (*) Laboratory of Agrozoology, Department of Crop Protection, Ghent University, Coupure Links 653, 9000 Gent, Belgium e-mail: Gianni.Vandenborre@ugent.be; Guy.Smagghe@UGent.be E.J.M. Van Damme Laboratory of Biochemistry and Glycobiology, Department of Molecular Biotechnology, Ghent University, Coupure Links 653, 9000, Gent, Belgium e-mail: ElsJM.VanDamme@ugent.be Natural Products: Plant Lectins as Important Tools in Controlling Pest Insects Gianni Vandenborre, Els J.M. Van Damme, and Guy Smagghe I. Ishaaya and A.R. Horowitz (eds.), Biorational Control of Arthropod Pests, DOI 10.1007/978-90-481-2316-2_7, © Springer Science + Business Media B.V. 2009