B. mori Host Response to Bb Figure 5. Cluster analysis of basal metabolism pathways. Detailed expression profiles of functionally pathways related sets of genes. The gene ID of SilkDB are shown on the left (for each gene ID, we used the letter A to substitute letters BGIBMGA to simplify the expression) and the serial number of KEGG database are shown on the right. For a detailed view, see Table S1 and Table S4. doi:10.1371/journal.pone.0008098.g005 deoxynucleotidyltransferase (DNA-directed) (EC 2.7.7.7), containing four members. These two subfamilies are also involved in the purine metabolism pathway. Twenty of the 22 genes were upregulated. More genes of the purine metabolism pathway were modulated; 37 were modulated, 26 of which were upregulated. These genes included 15 types of enzymes that catalyze at least 15 typical biochemical reactions in the purine pathway. Genes coding 15 types of enzymes were upregulated, including 59-phosphoribosyl-5-amino-4-imidazolecarboxamide formyltransferase (EC 2.1.2.3), nucleoside-triphosphatase (EC 3.6.1.15) and so on. These results also show that Bb infection accelerates the silkworm nucleic acid metabolism. Cofactor and vitamin metabolism. Vitamins are essential small compounds to maintain normal activities. After Bb infection, cofactor and vitamin metabolic pathway genes were modulated, including genes from the porphyrin and chlorophyll metabolism PLoS ONE | www.plosone.org 6 December 2009 | Volume 4 | Issue 12 | e8098