Gene expression profiles in juvenile hormone biosynthetic organ compared to other tissues in Bombyx mori

Juvenile hormone (JH) is produced and secreted by corpora allata (CA) during larval stages. JH biosynthesis from acetyl-CoA includes 13 enzymatic steps. Genes for 10 of those enzymes have been identified from Bombyx mori. It was also reported that they are basically expressed selectively in CA. Genes for the other 3 enzymes were recently reported from other insects, i.e., farnesyl diphosphate pyrophosphatase (FPPP) from Drosophila and farnesol dehydrogenase (FolD) and farnesal dehydrogenase (FalD) from Aedes. In order to reveal the expression profiles of these genes in Bombyx CA and to find other candidate genes involved in JH biosynthesis, we performed a transcriptomic analysis in corpora cardiaca-CA (CC-CA) complexes using a custom-made DNA microarray on which sequences from CC-CA EST libraries and genome-widely predicted genes are loaded. CC-CA complexes vigorously expressed JH-biosynthetic genes identified in Bombyx as well as genes involved in methyl-group metabolism and ribosomal protein genes; this is suitable for JH production. Bombyx counterparts of Drosophila FPPP and Aedes FolD genes, however, showed quite low level of expression. On the other hand, some other genes probably encoding oxidoreductases were expressed highly and selectively in CC-CA complex. Their products might function as FolD and/or FalD in Bombyx. Microarray experiments were performed for RNA samples isolated from 2 batches of CC-CA complexes (CCCA1 and CCCA2, independent experiments), prothoracic glands (PG), brains (Br), fat bodies (FB), mid guts (MG), epidermis (Ep), Malpighan tubules (MT), salivary glands (SalG) of day-2 4th instar; testes (W3Ts) and ovaries (W3Ov) of day-10 5th instar (3 days after the beginning of wandering); and CC-CA complexes (V4CCCA) of day-4 5th instar larvae.