Whole brains, collected and fixed in 4% paraformaldehyde were immunolabelled as previously described [47] . In brief, they were sectioned at 50 mm thickness with a Leica Vibrating Microtome and stored in PBS at 4uC. Sections were treated with 0.1% Triton X-100 (Sigma-Aldrich) in PBS for 1 hour and blocked with 0.5% Bovine serum albumin (Sigma-Aldrich) in PBS (PBS/BSA) overnight at 4uC. Primary antibodies were diluted in 0.5% PBS/BSA and incubated on sections for 2 hours at 37uC. Antibodies and dilutions were: rabbit anti-IBA1-microglia marker PBS. Mouse Ig Blocking Reagent (Vector Laboratories) was used with mouse primary antibodies: anti-Human Neurofilament protein (DakoCytomation) 1:50, anti-NeuN, (Millipore) 1:50, and a mouse monoclonal antibody raised against whole HeV (AAHL). Bound primary antibody was detected with species-specific secondary antibodies conjugated to Alexa 488 or 568 (Invitrogen) diluted 1:200 in PBS/BSA for 2 hours at 37uC. Sections were washed 3 times for 5 minutes with PBS and nuclei labelled with DAPI diluted 1:1000 in dH 2 O for 30 minutes. Sections were rinsed twice with dH 2 O, mounted with Vectashield Mounting Medium (Vector Laboratories) and coverslips sealed with nail varnish. Ipomoelin, a Jacalin-Related Lectin with a Compact Tetrameric Association and Versatile Carbohydrate Binding Properties Regulated by Its N Terminus Many proteins are induced in the plant defense response to biotic stress or mechanical wounding. One group is lectins. Ipomoelin (IPO) is one of the wound-inducible proteins of sweet potato (Ipomoea batatas cv. Tainung 57) and is a Jacalin-related lectin (JRL). In this study, we resolved the crystal structures of IPO in its apo form and in complex with carbohydrates such as methyl α-D-mannopyranoside (Me-Man), methyl α-D-glucopyranoside (Me-Glc), and methyl α-D-galactopyranoside (Me-Gal) in different space groups. The packing diagrams indicated that IPO might represent a compact tetrameric association in the JRL family. The protomer of IPO showed a canonical β-prism fold with 12 strands of β-sheets but with 2 additional short β-strands at the N terminus. A truncated IPO (ΔN10IPO) by removing the 2 short β-strands of the N terminus was used to reveal its role in a tetrameric association. Gel filtration chromatography confirmed IPO as a tetrameric form in solution. Isothermal titration calorimetry determined the binding constants (K(A)) of IPO and ΔN10IPO against various carbohydrates. IPO could bind to Me-Man, Me-Glc, and Me-Gal with similar binding constants. In contrast, ΔN10IPO showed high binding ability to Me-Man and Me-Glc but could not bind to Me-Gal. Our structural and functional analysis of IPO revealed that its compact tetrameric association and carbohydrate binding polyspecificity could be regulated by the 2 additional N-terminal β-strands. The versatile carbohydrate binding properties of IPO might play a role in plant defense. Plant defense is a complicated mechanism in response to mechanical wounding, herbivore and microorganism attack. Many proteins, namely wound-inducible proteins, are expressed to prevent pathogen infection, inhibit digestion by insects, and repair injured tissues [1, 2] . One group of wound-inducible proteins is lectin, the carbohydrate binding protein [3, 4] . Plant lectins are involved in the plant defense mechanism because of carbohydrate binding properties [5] [6] [7] [8] [9] . The toxicity of lectins was also confirmed in animal experiments [10, 11] . Plant lectins show resistance to digestive enzymes and can bind selectively to the carbohydrate moieties of gut epithelial cells to interfere in nutrient digestion and absorption [12] , so they could be a natural insecticide. In addition, plant lectins have been used for blood typing and immunological assay. The lectin concanavalin A is commercially used in affinity chromatography for purifying glycoproteins. Plant lectins have long been reported as potential inhibitors of viruses [13] [14] [15] [16] [17] .