Temperature-sensitive mutations in Drosophila melanogaster: X. Developmental analysis of the paralytic mutation, parats☆☆☆★

摘要

Therecessive,sex-linkedmutation,paralytictemperature-sensitive(parats),causesareversibletemperaturedependentparalysisinadultfliesonly.Whenadultparatsfliesareshiftedfrom22?°Cto29?°C,theyareparalyzedinlessthan5sec;ashiftbackto22?°Crestoresmobilityalmostinstantly.Somaticcuticularmosaicsofmutantandwild-typetissuewerecreatedbylossofanunstableringXchromosome.Thebehaviorof310(outof371)ofthesemosaicswasanalyzedat29?°C.Therelationshipbetweenthelocationofmutanttissueandthepatternofaberrantbehaviorat29?°Cwasanalyzedindetailwithaviewtoananatomicallocalizationofthedefectcausedbyparats.Manymosaicsfellintooneofthefollowingtencategorieswhosebehaviorisdiscussedindetail:abdomenonly,completehead,bilateralhead,completethorax,bilateralthorax,legonly,completehead-thorax,completehead-bilateralthorax,bilateralhead-completethorax,andbilateralhead-thorax.Themosaicdatasuggestthatthemutationisautonomous(i.e.,mutantcellsarenotaffectedbysurroundingwild-typetissue)andthatitrepresentsalesioninnervoustissue.Theresultsfromelectroretinogramsandoptomotortestssuggestthatthemutationdoesnotaffecttheabilityoftheeyetoreceiveandtransducelightintoimpulsesintheretinulacells,butthattheimpulseseitherdonotreachorcannotbeinterpretedbythebrain.Thus,paratsaffectsthecentralnervoussystem.Survivalofcompletelyparatsflieswithprolongedexposuretohightemperaturesuggeststhatvitalorganscontinuetofunctionduringparalysis.Indeed,theheartwasobservedtobeatquitenormally.Thisindicatesthatparatsdoesnoteffectthestomodealganglionoftheautonomicnervoussystem.Itisconcludedthatparatsaffectsatleasttwocomponentsofthecentralnervoussystem:(1)theheadincludingthebrainandsubesophagealganglion,and(2)thefusedthoracicganglialocatedintheventralregionofthethorax.