Developmental and hormonal regulation of midgut remodeling in a lepidopteran insect, Heliothis virescens

R. Parthasarathy, Subba R. Palli

Research output: Contribution to journalArticlepeer-review

95 Scopus citations

Abstract

Midgut tissue undergoes remodeling during metamorphosis in insects belonging to orders Lepidoptera and Diptera. We investigated the developmental and hormonal regulation of these remodeling events in lepidopteran insect, Heliothis virescens. In H. virescens, programmed cell death (PCD) of larval midgut cells as well as proliferation and differentiation of imaginal cells began at 108 h after ecdysis to the final larval instar (AEFL) and proceeded through the pupal stages. Expression patterns of pro- cell death factors (caspase-1 and ICE) and anti-cell death factor, Inhibitor of Apoptosis (IAP) were studied in midguts during last larval and pupal stages. IAP, Caspase-1 and ICE mRNAs showed peaks at 48 h AEFL, 96 h AEFL and in newly formed pupae, respectively. Immunohistochemical analysis substantiated high caspase-3 activity in midgut at 108 h AEFL. Application of methoprene, a juvenile hormone analog (JHA) blocked PCD by maintaining high levels of IAP, downregulating the expression of caspase-1, ICE and inhibiting an increase in caspase-3 protein levels in midgut tissue. Also, the differentiation of imaginal cells was impaired by methoprene treatment. These studies demonstrate that presence of JHA during final instar larvae affects both midgut remodeling and larval-pupal metamorphosis leading to larval/pupal deformities in lepidopteran insects, a mechanism that is different from that in mosquito, Ae. aegypti where JHA uncouples midgut remodeling from metamorphosis.

Original languageEnglish
Pages (from-to)23-34
Number of pages12
JournalMechanisms of Development
Volume124
Issue number1
DOIs
StatePublished - Jan 2007

Bibliographical note

Funding Information:
This work was supported by National Research Initiative of the USDA-CSREES (2004-03070). We thank Dr. Sharyn Perry and Dr. Doug Harrison from University of Kentucky for use of their histology facilities and confocal microscope. This is contribution number 06-08-075 from the Kentucky Agricultural Experimental Station.

Keywords

  • Caspases
  • Development
  • Gene expression
  • Hormones
  • Inhibitor of apoptosis
  • Methoprene
  • Programmed cell death

ASJC Scopus subject areas

  • Embryology
  • Developmental Biology

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