Hexamerin-based regulation of juvenile hormone-dependent gene expression underlies phenotypic plasticity in a social insect

Xuguo Zhou, Matthew R. Tarver, Michael E. Scharf

Research output: Contribution to journalArticlepeer-review

92 Scopus citations

Abstract

Worker termites of the genus Reticulitermes are temporally-arrested juvenile forms that can terminally differentiate into adult-soldier- or reproductive-caste phenotypes. Soldier-caste differentiation is a developmental transition that is induced by high juvenile hormone (JH) titers. Recently, a status quo hexamerin mechanism was identified, which reduces JH efficacy and maximizes colony fitness via the maintenance of high worker-caste proportions. Our goal in these studies was to investigate more thoroughly the influences of the hexamerins on JH-dependent gene expression in termite workers. Our approach involved RNA interference (RNAi), bioassays and quantification of gene expression. We first investigated the expression of 17 morphogenesis-associated genes in response to RNAi-based hexamerin silencing. Hexamerin silencing resulted in significant downstream impacts on 15 out of the 17 genes, suggesting that these genes are members of a JH-responsive genomic network. Next, we compared gene-expression profiles in workers after RNAi-based hexamerin silencing to that of (i) untreated workers that were held away from the colony; and (ii) workers that were also held away from the colony, but with ectopic JH. Here, although there was no correlation between hexamerin silencing and colony-release effects, we observed a significant correlation between hexamerin silencing and JH-treatment effects. These findings provide further evidence supporting the hypothesis that the hexamerins modulate JH availability, thus limiting the impacts of JH on termite caste polyphenism. Results are discussed in a context relative to outstanding questions on termite developmental biology, particularly on regulatory gene networks that respond to JH-, colony- and environmental-cues.

Original languageEnglish
Pages (from-to)601-610
Number of pages10
JournalDevelopment (Cambridge)
Volume134
Issue number3
DOIs
StatePublished - Feb 2007

Keywords

  • Hexamerin
  • Juvenile hormone
  • Phenotypic plasticity
  • RNA interference
  • Reticulitermes
  • Short-interfering RNA
  • Sociogenomics

ASJC Scopus subject areas

  • Molecular Biology
  • Developmental Biology

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