Hormonal control of a metamorphosis-specific transcriptional factor Broad-Complex in silkworm.
Insect metamorphosis is induced by the steroid 20-hydroxyecdysone (20E) in the absence of sesquiterpenoid juvenile hormone (JH). In Drosophila melanogaster, the Broad-Complex (BR-C) transcriptional factor plays critical roles during metamorphosis. We isolated cDNAs encoding BR-C in the silkworm Bombyx mori and examined their mRNA expression. cDNAs for three BR-C isoforms with zinc finger pairs (Z1, Z2 and Z4) and four isoforms lacking them were cloned. Their mRNAs were expressed in multiple tissues at the larval-pupal metamorphosis. In the anterior silk gland, BR-C mRNAs were expressed at the end of the last larval instar but not expressed during the penultimate instar. 20E administration induced BR-C mRNA expression and JH suppressed 20E-induced BR-C expression in this tissue both in vivo and in vitro. Thus, BR-C mRNAs are inducible by 20E only in the absence of JH, a finding that explains their metamorphosis-specific expression.
Reza
A M S
AM
Developmental Biology Department, National Institute of Agrobiological Sciences, 1-2, Owashi, Tsukuba, Ibaraki 305-8634, Japan.
Kanamori
Y
Y
Shinoda
T
T
Shimura
S
S
Mita
K
K
Nakahara
Y
Y
Kiuchi
M
M
Kamimura
M
M
D000818:Animals; D012831:Bombyx / Q000235:genetics / Q000502:physiology*; D004331:Drosophila melanogaster / Q000235:genetics; D004441:Ecdysterone / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental / Q000235:genetics / Q000502:physiology*; D007605:Juvenile Hormones / Q000235:genetics / Q000378:metabolism*; D007814:Larva / Q000235:genetics / Q000502:physiology; D008675:Metamorphosis, Biological / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D007605:Juvenile Hormones; D012333:RNA, Messenger; D014157:Transcription Factors; D004441:Ecdysterone