Natural Products: Plant Lectins as Important Tools in Controlling Pest Insects

Abstract

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 developed several chemical defense strategies towards herbivorous insects. These defense chemicals include plant secondary metabolites and proteins that can reduce the nutrient 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 including 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 specificity. Based on sequence similarity, plant lectins can be divided in different subgroups of structurally and evolutionary related proteins (Table 1).