2005 Fiscal Year Final Research Report Summary
Genomic action of steroid hormone in the silkworm brain during morphogenesis.
| Project/Area Number |
15580039
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied entomology
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| Research Institution | Kanazawa University |
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Principal Investigator |
IWAMI Masafumi Kanazawa University, Graduate School of Natural Science and Technology, Professor, 自然科学研究科, 教授 (40193768)
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| Co-Investigator(Kenkyū-buntansha) |
SAKURAI Sho Kanazawa University, Graduate School of Natural Science and Technology, Professor, 自然科学研究科, 教授 (80143874)
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| Project Period (FY) |
2003 – 2005
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| Keywords | ecdysone / brain / silkworm / morphogenesis / metamorphosis / receptor / gene expression / insect |
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| Research Abstract |
The steroid hormone, 20-hydroxyecdysone (20E), triggers the major developmental transitions of insects including molting and metamorphosis. 20E regulates target genes directly through the receptor and executes development. The dynamic morphological changes of the brain during metamorphosis such as the formation of optic lobes are also caused by 20E action. In the silkworm Bombyx mori, the 20E level is controlled by the prothoracicotropic hormone (PTTH) and PTTH is produced by the two pairs of lateral neurosecretory cells in the brain. Beside PTTH, the brain produces peptide hormones necessary for metamorphosis. The insect brain is thus the center of insect developmental control and the 20E action in the brain governs the post-embryonic development including the morphological change of the brain itself. However, the genomic response to 20E in the brain during metamorphosis has not been identified systematically.
We therefore performed comprehensive expression analysis of the 20E-responsive genes of Bombyx brain with a microarray on which over 80% of total Bombyx genes are arranged and with a 20E-inducible cDNA library. We focused on the direct genomic response by 20E during metamorphosis and have identified 93 up-regulated and 97 down-regulated genes from the microarray and at least 7 genes from the cDNA library. In situ hybridization showed that major expression site of these genes characterized is at the PTTH-producing cells (PTPCs). One of the ecdysone receptor complex genes, EcR-A is also up-regulated by 20E and their mRNAs were detected exclusively in PTPCs in the larval brain. This result indicates that PTPCs are the major 20E-responsive cells in the larval brain and suggests that PTPCs are the master cells of insect metamorphosis.
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