B. mori Host Response to Bb Figure 6. Functional groups of silkworm poisoning related genes. (a) Cluster analysis of silkworm poisoning related genes referencing to Bacillus thuringiensis toxins. For a detailed view of the cluster ratios, see Table S4. (b) SEM pictures of the silkworm middle gut epithelium after Bb infection. The pictures showed Bb crystals accumulated in the host intestinal epithelial cells and pores were formed in the host intestinal epithelial cells after Bb oral infection. (c) Schematic overview of the process that Bb damage silkworm midgut, into the hemolymph. After oral infection, Bb interred the ingestion of silkworm. The parasporal crystal (PC) produced by Bb could be digested by midgut proteases. The digested PC could pass through the peritrophic membrane (PM) to bind the aminopeptidase N receptors (APNs) of the midgut epithelial cells to damage them. Bb can go to hemolymph from the damaged midgut. doi:10.1371/journal.pone.0008098.g006 PLoS ONE | www.plosone.org 8 December 2009 | Volume 4 | Issue 12 | e8098