Experimental reversal of the normal dorsal-ventral timing of blastopore formation does not reverse axis polarity in Xenopus laevis embryos☆

摘要

DuringgastrulationinXenopuslaevis,thedorsallipoftheblastoporenormallyappearsbeforetheventrallip.Metabolicgradientmodelsproposethatthedorsallipdevelopsfromtheregionofhighestmetabolicactivityandsomehowdominatesotherregionstopreventthemfrombecomingdorsal.Totesttheseideas,Iappliedatemperaturegradientof12?°Cacrosstheembryo.Localizedheatingoftheprospectiveventralvegetalregionfromearlyinthefirstcleavageperioduntilgastrulationcausestheblastoporeliptoformfirstby2hrattheprospectiveventralmeridianratherthanattheprospectivedorsalmeridian.Despitethisreversalofthetimingofblastoporeformation,gastrulationiscompleted,andtheneuralplateformsatitsusualpositionontheprospectivedorsalmeridian.Thisdemonstratesthattheearliestgastrulatingregionsoftheblastoporedonotnecessarilybecomedorsal,nordotheyinhibitdorsaldevelopmentbyotherregions.Itisunlikelythataxispolarityisbasedonregionaldifferencesinenergymetabolism.