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1 May 2012 Identification of 20-Hydroxyecdysone-Inducible Genes from Larval Brain of the Silkworm, Bombyx mori, and Their Expression Analysis
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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.

© 2012 Zoological Society of Japan
Anuradha Roy, Sakiko Shimizu, Taketoshi Kiya, Kazuei Mita, and Masafumi Iwami "Identification of 20-Hydroxyecdysone-Inducible Genes from Larval Brain of the Silkworm, Bombyx mori, and Their Expression Analysis," Zoological Science 29(5), 333-339, (1 May 2012).
Received: 25 September 2011; Accepted: 1 December 2011; Published: 1 May 2012

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