Patterns of MHR3 expression in the epidermis during a larval molt of the tobacco hornworm Manduca sexta

Rosalie E. Langelan, Jeffrey E. Fisher, Kiyoshi Hiruma, Subba Reddy Palli, Lynn M. Riddiford

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


MHR3, an ecdysone-induced transcription factor, was shown to appear in the abdominal epidermis of the tobacco hornworm Manduca sexta in a pattern-specific manner as the 20-hydroxyecdysone (20E) titer rises for the larval molt. The crochet epidermis that forms the hooked setae on the proleg is first to show MHR3 mRNA and protein followed sequentially by the spiracle, the dorsal intrasegmental annuli, the interannular regions, and finally the trichogen and tormogen cells. The protein appears in the nuclei about 8 h before the onset of cuticle formation, is present during the outgrowth of the setae, and disappears after epicuticle formation. In vitro studies showed that MHR3 mRNA induction in the crochet epidermis by 20E was more sensitive (EC50 = 10−6 M; 50% induction by 2 h exposure to 4 x 10−6 M 20E) and did not require protein synthesis for maximal accumulation compared to the dorsal epidermis. The ecdysone receptor complex is present in both tissues at the outset of the molt and therefore is not a determining factor in these responses. Thus, in addition to the ecdysone receptor complex, region-specific factors govern both sensitivity and timing of responsiveness of MHR3 to 20E to ensure that this transcription factor will be present when needed for its differentiative role. (C) 2000 Academic Press.

Original languageEnglish
Pages (from-to)481-494
Number of pages14
JournalDevelopmental Biology
Issue number2
StatePublished - Nov 15 2000

Bibliographical note

Funding Information:
We thank Dr. James S. Warren and Professor Lawrence Gilbert, University of North Carolina, for the HPLC-RIA analysis of the ecdysteroids present in the hemolymph; Dr. Sho Sakurai, Ka-nazawa University, for the O-6 antibody; Dr. Wendy Smith, North-eastern University, for help with the RIA protocol and for providing protein A for the assay; Dr. Takeshi Matsumoto, Daicel Chemical Co., for 20E; Drs. David Champlin and Que Lan for the affinity-purified antiMHR3 antibody; Ta Deng for assistance in some of the immunocytochemistry; and Drs. James Truman and Margrit Schu-biger for critical comments on the manuscript. The work was supported by grants from NIH (AI 12495) and NSF (IBN 95-14187 and IBN 98-17339).


  • 20-hydroxyecdysone
  • Abdominal epidermis
  • MHR3
  • Manduca sexta
  • Transcription factor patterning

ASJC Scopus subject areas

  • Molecular Biology
  • Developmental Biology
  • Cell Biology


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