An ecdysteroid-inducible Manduca gene similar to the Drosophila DHR3 gene, a member of the steroid hormone receptor superfamily

Subba Reddy Palli, Kiyoshi Hiruma, Lynn M. Riddiford

Research output: Contribution to journalArticlepeer-review

117 Scopus citations

Abstract

Using cDNAs for the human retinoic acid receptor α (hRARα) and Drosophila hormone receptor 3 (DHR3), we isolated a cDNA encoding a member of the steroid hormone receptor superfamily from the tobacco hornworm, Manduca sexta. Sequencing showed that this cDNA is most closely related to DHR3 (97 and 68% amino acid identity in the DNA and ligand binding regions, respectively) followed by hRARα (65 and 20% identity, respectively) and therefore is named MHR3. The cDNA hybridized to two mRNAs (3.8 and 4.5 kb) found in the epidermis during the ecdysteroid rises for the embryonic, larval, and pupal molts. Culture of fourth instar larval epidermis with 4 μM 20-hydroxyecdysone (2 μg/ml 20HE) caused the appearance of MHR3 mRNA within 3 hr and maximal expression by 6 hr; after 12 hr continuous exposure to 20HE, the mRNA level declined. The 4.5-kb mRNA appeared first, both were present in equal amounts by 12 hr, and by 20 hr the predominant transcript was 3.8 kb. Similar 20HE-induced expression was seen in epidermis explanted 1 day after the onset of wandering, although with a slower time course. The induction was largely independent of protein synthesis, but the subsequent decline required protein synthesis as is typical of the "early" puffs in Drosophila. Continuous exposure to 20HE was necessary for MHR3 expression; in its absence, the mRNA declined with a half-life of 2 hr. Thus, MHR3 is an ecdysteroid-inducible DNA binding protein that likely is a transcription factor involved in the cascade of gene activation and inactivation caused by ecdysteroids during the insect molt.

Original languageEnglish
Pages (from-to)306-318
Number of pages13
JournalDevelopmental Biology
Volume150
Issue number2
DOIs
StatePublished - Apr 1992

Bibliographical note

Funding Information:
We thank Dr. Pierre Chambon for the human retinoic acid receptor cDNA clone; Mr. Michael Koelle and Professor David Hogness for the Southern blot of Drosophila receptor cDNAs and for the DHR3 cDNA, and Professor James W. Truman for critical comments on the manuscript. Supported by NSF DCB88-188’76 and NIH AI12.459.

ASJC Scopus subject areas

  • Molecular Biology
  • Developmental Biology
  • Cell Biology

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