title: Identification of 20-hydroxyecdysone-inducible genes from larval brain of the silkworm, Bombyx mori, and their expression analysis.
abstract: The insect brain secretes prothoracicotropic hormone (PTTH), which stimulates the prothoracic gland to synthesize ecdysone. The active metabolite of ecdysone, 20-hydroxyecdysone (20E), works through ecdysone receptor (EcR) and ultraspiracle (USP) to initiate molting and metamorphosis by regulating downstream genes. Previously, we found that EcR was expressed in the PTTH-producing neurosecretory cells (PTPCs) in larval brain of the silkworm Bombyx mori, suggesting that PTPCs function as the master cells of development under the regulation of 20E. To gain a better understanding of the molecular mechanism of the 20E control of PTPCs, we performed a comprehensive screening of genes induced by 20E using DNA microarray with brains of day-2 fifth instar silkworm larvae. Forty-one genes showed greater than twofold changes caused by artificial application of 20E. A subsequent semiquantitative screening identified ten genes upregulated by 20E, four of which were novel or not previously identified as 20E-response genes. Developmental profiling determined that two genes, UP4 and UP5, were correlated with the endogenous ecdysteroid titer. Whole-mount in situ hybridization showed exclusive expression of these two genes in two pairs of cells in the larval brain in response to 20E-induction, suggesting that the cells are PTPCs. BLAST searches revealed that UP4 and UP5 are Bombyx homologs of vrille and tarsal-less, respectively. The present study identifies 20E-induced genes that may be involved in the ecdysone signal hierarchies underlying pupal-adult development and/or the 20E regulation of PTPCs.
authors.affiliation: Division of Life Sciences, Graduate school of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
authors.forename: Anuradha
authors.initials: A
authors.lastname: Roy
authors.forename: Sakiko
authors.initials: S
authors.lastname: Shimizu
authors.forename: Taketoshi
authors.initials: T
authors.lastname: Kiya
authors.forename: Kazuei
authors.initials: K
authors.lastname: Mita
authors.forename: Masafumi
authors.initials: M
authors.lastname: Iwami
mesh_terms: D000818:Animals; D012831:Bombyx / Q000187:drug effects* / Q000378:metabolism*; D001921:Brain / Q000187:drug effects* / Q000378:metabolism*; D004441:Ecdysterone / Q000494:pharmacology*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000187:drug effects*; D007814:Larva / Q000187:drug effects / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis
chemical_list: D004441:Ecdysterone