even-skipped has gap-like, pair-rule-like, and segmental functions in the cricket Gryllus bimaculatus, a basal, intermediate germ insect (Orthoptera)

摘要

Developmentalmechanismsofsegmentationappeartobevariedamonginsectsinspiteoftheirconservedbodyplan.Althoughtheexpressionpatternsofthesegmentpolaritygenesinallinsectsexaminedimplywellconservedfunctionofthisclassofgenes,expressionpatternsandfunctionofthepair-rulegenestendtoexhibitdiversity.Togainfurtherinsightsintotheevolutionofthesegmentationprocessandtheroleofpair-rulegenes,wehaveexaminedexpressionandfunctionofanorthologoftheemDrosophila/empair-rulegeneemeven-skipped/em(emeve/em)inaphylogeneticallybasalinsect,emGryllusbimaculatus/em(Orthoptera,intermediategermcricket).WefindthatemGrylluseve/em(emGb'eve/em)isexpressedasstripesineachoftheprospectivegnathal,thoracic,andabdominalsegmentsandasabroaddomainintheposteriorgrowthzone.DynamicsofstripeformationvaryamongemGb/em'emeve/emstripes,representingoneofthethreemodes,thesegmental,incompletepair-rule,andcompletepair-rulemode.Furthermore,wefindthatRNAisuppressionofemGb'eve/emresultsinsegmentationdefectsinbothanteriorandposteriorregionsoftheembryo.MilddepletionofemGb'eve/emshowsapair-rule-likedefectinanteriorsegments,whilestrongerdepletioncausesagap-likedefectshowingdeletionofanteriorandposteriorsegments.TheseresultssuggestthatemGb'eve/emactsasapair-rulegeneatleastduringanteriorsegmentationandalsohassegmentalandgap-likefunctions.Additionally,emGb'eve/emmaybeinvolvedintheregulationofemhunchback/emandemKruuml;ppel/emexpression.Comparisonswithemeve/emfunctionsinotherspeciessuggestthattheemGb'eve/emfunctionmayrepresentanintermediatestateoftheevolutionofpair-rulepatterningbyemeve/emininsects./p/div