DNA synthesis and cell division during second pupal development in the silkmoth, Antheraea polyphemus

Mary F. Ruh, Robert G. Brzyski, Natalie A. Connors, Kevin A. Dwyer

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

Chilled pupae of Antheraea polyphemus were induced to form second pupae by injecting juvenile hormone (JH) alone or with 20-hydroxyecdysone (20-HE). Adults were permitted to initiate development spontaneously or by injection of 20-HE. During development, wing tissue was removed for measurement of incorporation of [3H]-thymidine ([3H]-TdR) into DNA and the total DNA content. Tissue samples were also obtained for histological examination. Wing tissue from pupae stimulated by injected 20-HE alone or with JH, incorporated [3H]-TdR maximally on day 1. The incorporation values then declined to control levels by day 4, and continued low to day 6. Animals which initiated development spontaneously either in the presence or absence of JH had a more gradual increase in the rate of DNA synthesis with the peak rate occurring on days 2-3. Studies of the cellular ratio of thymidine triphosphate to thymidine (TTP/TdR) indicated that the incorporation of [3H]-TdR into DNA was the result of hormone stimulation of TdR metabolism and not merely the result of increased cellular uptake of DNA precursors into epidermal cells. The DNA content of all experimental groups parallelled the changes in the rate of DNA synthesis. Wing DNA levels during 20-HE synchronized second pupal and adult development increased up to day 6 and then remained constant until day 12, when DNA content decreased significantly in second pupae. Light microscopy indicated that epidermal cells of 20-HE synchronized developing second pupae and pharate adults divided between one and two days after hormone injection. At four days, differentiated scale cells were seen in adults but were never seen in second pupae. These results suggest that DNA synthesis is initiated by ecdysteroids, regardless of whether the steroid is injected or released endogenously, and that JH itself has no specific effects on DNA synthesis or proliferative cell divisions in the wing.

Original languageEnglish (US)
Pages (from-to)607-616
Number of pages10
JournalInsect Biochemistry
Volume10
Issue number6
DOIs
StatePublished - 1980
Externally publishedYes

Keywords

  • cell division
  • DNA synthesis
  • Juvenile hormone
  • second pupae

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