Ecdysone signaling opposes epidermal growth factor signaling in regulating cyst differentiation in the male gonad of Drosophila melanogaster

摘要

Thedevelopmentofstemcelldaughtersintothedifferentiatedstatenormallyrequiresacascadeofproliferationanddifferentiationstepsthataretypicallyregulatedbyexternalsignals.Thegermlinecellsofmostanimals,inspecific,areassociatedwithsomaticsupportcellsanddependonthemfornormaldevelopment.InthemalegonadofemDrosophilamelanogaster/em,germlinecellsarecompletelyenclosedbycytoplasmicextensionsofsomaticcystcells,andthesecystsformafunctionalunit.SignalingfromthegermlinetothecystcellsviatheEpidermalGrowthFactorReceptor(EGFR)isrequiredforgermlineenclosureandhasbeenproposedtoprovideatemporalsignaturepromotingearlystepsofdifferentiation.Atemperature-sensitivealleleoftheEGFRligandSpitz(Spi)providesapowerfultoolforprobingthefunctionoftheEGRFpathwayinthiscontextandforidentifyingotherpathwaysregulatingcystdifferentiationviageneticinteractionstudies.Usingthistool,weshowthatsignalingviatheEcdysoneReceptor(EcR),aknownregulatorofdevelopmentaltimingduringlarvalandpupaldevelopment,opposesEGFsignalingintestes.Inemspi/emmutantanimals,reducingeitherEcdysonesynthesisortheexpressionofEcdysonesignaltransducersortargetsinthecystcellsresultedinarescueofcystformationandcystdifferentiation.Despiteofthisstrikingeffectintheemspi/emmutantbackgroundandtheexpressionofEcRsignalingcomponentswithinthecystcells,activityoftheEcRpathwayappearstobedispensableinawildtypebackground.WeproposethatEcRsignalingmodulatestheeffectsofEGFRsignalingbypromotinganundifferentiatedstateinearlystagecystcells./p/div