A command chemical triggers an innate behavior by sequential activation of multiple peptidergic ensembles.
BACKGROUND
At the end of each molt, insects shed their old cuticle by performing the ecdysis sequence, an innate behavior consisting of three steps: pre-ecdysis, ecdysis, and postecdysis. Blood-borne ecdysis-triggering hormone (ETH) activates the behavioral sequence through direct actions on the central nervous system.


RESULTS
To elucidate neural substrates underlying the ecdysis sequence, we identified neurons expressing ETH receptors (ETHRs) in Drosophila. Distinct ensembles of ETHR neurons express numerous neuropeptides including kinin, FMRFamides, eclosion hormone (EH), crustacean cardioactive peptide (CCAP), myoinhibitory peptides (MIP), and bursicon. Real-time imaging of intracellular calcium dynamics revealed sequential activation of these ensembles after ETH action. Specifically, FMRFamide neurons are activated during pre-ecdysis; EH, CCAP, and CCAP/MIP neurons are active prior to and during ecdysis; and activity of CCAP/MIP/bursicon neurons coincides with postecdysis. Targeted ablation of specific ETHR ensembles produces behavioral deficits consistent with their proposed roles in the behavioral sequence.


CONCLUSIONS
Our findings offer novel insights into how a command chemical orchestrates an innate behavior by stepwise recruitment of central peptidergic ensembles.
Kim
Young-Joon
YJ
Department of Entomology, 5429 Boyce Hall, University of California, Riverside, 92521, USA.
Zitnan
Dusan
D
Galizia
C Giovanni
CG
Cho
Kook-Ho
KH
Adams
Michael E
ME
D000818:Animals; D030801:Animals, Genetically Modified; D001522:Behavior, Animal; D002118:Calcium / Q000378:metabolism; D002490:Central Nervous System / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D004330:Drosophila / Q000033:anatomy & histology / Q000254:growth & development*; D019835:FMRFamide / Q000378:metabolism; D007301:Insect Hormones / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D008969:Molecular Sequence Data; D018978:Molting / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D009479:Neuropeptides / Q000378:metabolism*; D010641:Phenotype; D018000:Receptors, Peptide / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction
D007301:Insect Hormones; D009479:Neuropeptides; D018000:Receptors, Peptide; C474803:ecdysis-triggering hormone receptor, Drosophila; C403307:ecdysis-triggering hormone, Drosophila; D019835:FMRFamide; D002118:Calcium