E74 exhibits stage-specific hormonal regulation in the epidermis of the tobacco hornworm, manduca sexta.
The transcription factor E74 is one of the early genes induced by ecdysteroids during metamorphosis of Drosophila melanogaster. Here, we report the cloning and hormonal regulation of E74 from the tobacco hornworm, Manduca sexta (MsE74). MsE74 is 98% identical to that of D. melanogaster within the DNA-binding ETS domain of the protein. The 5'-isoform-specific regions of MsE74A and MsE74B share significantly lower sequence similarity (30-40%). Developmental expression by Northern blot analysis reveals that, during the 5th larval instar, MsE74B expression correlates with pupal commitment on day 3 and is induced to maximal levels within 12h by low levels of 20-hydroxyecdysone (20E) and repressed by physiologically relevant levels of juvenile hormone I (JH I). Immunocytochemical analysis shows that MsE74B appears in the epidermis before the 20E-induced Broad transcription factor that is correlated with pupal commitment (Zhou and Riddiford, 2001). In contrast, MsE74A is expressed late in the larval and the pupal molts when the ecdysteroid titer has declined to low levels and in the adult molt just as the ecdysteroid titer begins to decline. This change in timing during the adult molt appears not to be due to the absence of JH as there was no change during the pupal molt of allatectomized animals. When either 4th or 5th instar larval epidermis was explanted and subjected to hormonal manipulations, MsE74A induction occurred only after exposure to 20E followed by its removal. Thus, MsE74B appears to have a similar role at the onset of metamorphosis in Manduca as it does in Drosophila, whereas MsE74A is regulated differently at pupation in Manduca than at pupariation in Drosophila.
Stilwell
Geoffrey E
GE
Department of Biology, University of Washington, Box 351800, Seattle, WA 98195-1800, USA.
Nelson
Charles A
CA
Weller
John
J
Cui
Haiyang
H
Hiruma
Kiyoshi
K
Truman
James W
JW
Riddiford
Lynn M
LM
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D004330:Drosophila / Q000196:embryology / Q000378:metabolism; D004441:Ecdysterone / Q000494:pharmacology / Q000502:physiology; D000078404:Epidermal Cells; D004817:Epidermis / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D017344:Genes, Insect / Q000187:drug effects; D019476:Insect Proteins / Q000737:chemistry / Q000378:metabolism*; D007605:Juvenile Hormones / Q000494:pharmacology / Q000502:physiology; D007814:Larva / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D018402:Manduca / Q000196:embryology* / Q000378:metabolism; D008675:Metamorphosis, Biological / Q000187:drug effects / Q000235:genetics; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D020033:Protein Isoforms / Q000737:chemistry; D017434:Protein Structure, Tertiary; D011679:Pupa / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D019476:Insect Proteins; D007605:Juvenile Hormones; D020033:Protein Isoforms; D012333:RNA, Messenger; D014157:Transcription Factors; D004441:Ecdysterone