Differential Expression of Ecdysone Receptor Leads to Variation in Phenotypic Plasticity across Serial Homologs

PLoS Genet. 2015 Sep 25;11(9):e1005529. doi: 10.1371/journal.pgen.1005529. eCollection 2015.


Bodies are often made of repeated units, or serial homologs, that develop using the same core gene regulatory network. Local inputs and modifications to this network allow serial homologs to evolve different morphologies, but currently we do not understand which modifications allow these repeated traits to evolve different levels of phenotypic plasticity. Here we describe variation in phenotypic plasticity across serial homologous eyespots of the butterfly Bicyclus anynana, hypothesized to be under selection for similar or different functions in the wet and dry seasonal forms. Specifically, we document the presence of eyespot size and scale brightness plasticity in hindwing eyespots hypothesized to vary in function across seasons, and reduced size plasticity and absence of brightness plasticity in forewing eyespots hypothesized to have the same function across seasons. By exploring the molecular and physiological causes of this variation in plasticity across fore and hindwing serial homologs we discover that: 1) temperature experienced during the wandering stages of larval development alters titers of an ecdysteroid hormone, 20-hydroxyecdysone (20E), in the hemolymph of wet and dry seasonal forms at that stage; 2) the 20E receptor (EcR) is differentially expressed in the forewing and hindwing eyespot centers of both seasonal forms during this critical developmental stage; and 3) manipulations of EcR signaling disproportionately affected hindwing eyespots relative to forewing eyespots. We propose that differential EcR expression across forewing and hindwing eyespots at a critical stage of development explains the variation in levels of phenotypic plasticity across these serial homologues. This finding provides a novel signaling pathway, 20E, and a novel molecular candidate, EcR, for the regulation of levels of phenotypic plasticity across body parts or serial homologs.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Biological Evolution
  • Butterflies / genetics
  • Butterflies / growth & development*
  • Ecdysterone / genetics*
  • Ecdysterone / metabolism
  • Gene Expression Regulation, Developmental
  • Gene Regulatory Networks
  • Phenotype
  • Pigmentation
  • Receptors, Steroid / genetics*
  • Selection, Genetic*
  • Signal Transduction
  • Wings, Animal / growth & development


  • Receptors, Steroid
  • ecdysone receptor
  • Ecdysterone

Grant support

We thank National Science Foundation (NSF) IOS 1146933 to AM and KLP, NSF PHY 0957680 to AM and HC, and Singapore Ministry of Education grant MOE 2014-T2-1-146 to AM for funding. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.