Genetic and developmental evidence for a repressed genital primordium in Drosophila melanogaster☆

[摘要] StudieswithchromosomalmosaicshaveindicatedthattheblastodermalanlageofthegenitaldiscofDrosophilaconsistsofthreeprimordia:oneforthefemalegenitalia,oneforthemalegenitalia,andonefortheanalia.Innormaldevelopment,onlyoneofthetwogenitalprimordiaformsadultderivativeswhereastheotherbecomesrepressed.Thepresentreportinvestigatesthefateoftherepressedprimordiaandanalyzesthefunctionofthetransformer(tra)geneinthedevelopmentofthegenitalprimordia(themutationtratransformschromosomalfemalesintomales).Therepressedmalegenitalprimordium(RMP)inthefemalediscwaslocalizedbydeterminingthesitefromwhichmalegenitalclonesweregrowing.Forthispurpose,cloneshomozygousfortraweregeneratedlateinthethirdinstarbyirradiatingfemalelarvaeheterozygousfortra+.Theirgenitaldiscswereculturedinvivotoallowforadditionalcellproliferationbeforemetamorphosis.Afterculture,19outof224discsshowedlocaloutgrowths,presumablyrepresentingtratraclones.Theseoutgrowthswerecutoutofthediscsandtransplantedintolarvae,wheretheymetamorphosedintomalegenitalstructures.Allcloneswerefoundintheanteriorthirdofthedorsaldiscepithelium.Ifisolatedfromanormalfemaledisc,thisregiondoesnotformanyadultstructures.Wethereforeassumethatitharborstherepressedmalegenitalprimordium(RMP).Theclonesalsodemonstratethattheactionoftra+iscontinuouslyrequiredtomaintainthefemalesexualpathway.TheintersexualgenitaldiscofthegenotypeXX;dsxD+exhibitswell-developedmaleandfemalegenitalprimordia.ThesiteofthemaleprimordiumcoincideswiththesiteoftheRMPasdeterminedabove.Thefemaleprimordiumislocatedintheventralepitheliumwherethenormalmalegenitaldischasaslighlyenlargedregionwhichdoesnotformanyknownimaginalstructures.Weproposethatthispartofthemaledisccontainstherepressedfemalegenitalprimoridum(RFP).

[学科分类] 生物科学（综合）