Functional analysis of Scr during embryonic and post-embryonic development in the cockroach, Periplaneta americana

摘要

Thecockroach,emPeriplanetaamericana/emrepresentsabasalinsectlineagethatundergoestheancestralhemimetabolousmodeofdevelopment.Here,weexaminetheembryonicandpost-embryonicfunctionsofthehoxgeneemScr/eminemPeriplaneta/emasawayofbetterunderstandingtherolesofthisgeneintheevolutionofinsectbodyplans.Duringembryogenesis,emScr/emfunctionisstrictlylimitedtotheheadwithnoroleintheprothorax.ThisindicatesthattheancestralembryonicfunctionofemScr/emwaslikelyrestrictedtothehead,andthattheposteriorexpansionofexpressionintheT1legsmayhaveprecededanyapparentgainoffunctionduringevolution.Inaddition,emScr/emplaysapivotalroleintheformationofthedorsalridge,astructurethatseparatestheheadandthoraxinallinsects.ThisisevidencedbythepresenceofasupernumerarysegmentthatoccursbetweenthelabialandT1segmentsofRNAiemScr/emfirstnymphsandisattributedtoanalterationinemengrailed/em(emen/em)expression.ThefactthatsimilaremScr/emphenotypesareobservedinemTribolium/embutnotinemDrosophila/emoremOncopeltus/emrevealsthepresenceoflineage-specificvariationinthegeneticarchitecturethatcontrolstheformationofthedorsalridge.Indirectcontrasttotheembryonicroles,emScr/emhasnofunctionintheheadregionduringpost-embryogenesisinemPeriplaneta/em,andinstead,strictlyactstoprovideidentitytotheT1segment.Furthermore,thestrongestemPeriplaneta/emRNAiemScr/emphenotypesdevelopectopicwing-liketissuethatoriginatesfromtheposteriorregionoftheprothoracicsegment.Thisfindingprovidesanovelinsightintothecurrentdebateonthemorphologicaloriginofinsectwings./p/div