Effects of α-ecdysone, β-ecdysone and inokosterone on the in vitro evagination of Drosophila leg discs and the subsequent differentiation of imaginal integumentary structures☆

[摘要] Themorphogeneticactivityofthreehormonalsubstances—α-ecdysone,β-ecdysone,andinokosterone—hasbeenstudiedinvitroonisolatedimaginallegdiscsofthird-instarlarvaeofDrosophilamelanogaster.Inthepresenceofα-ecdysone(0.3–3μg/ml)andalsoofthephytohormoneinokosterone(0.3–3μg/ml),thediscsunderwentmetamorphosis,ascharacterizedbycompleteevagination(inlessthan24hr),secretion,andshedding(48hrafterexplanation)ofthepupalcuticle,secretion,andstructuraldifferentiationoftheimaginalcuticle,namelypigmentationandformationofclaws,bristles,andhairs(duringdays3–6).Inthepresenceofβ-ecdysone(10,6,3,0.3,0.03,0.003μg/ml),evaginationwasalwaysabnormalandincomplete.Withallconcentrationsbutthelowest,thepartiallyevertedlegshadaswollenappearanceand,atallconcentrations,thesubsequentdevelopmentwasinhibited.Noimaginaldifferentiationoccurredatanyoftheconcentrationstested.Larvalfatbodyorlarvalepidermisaddedtotheisolateddiscshadnoinfluenceontheirresponsetoeitherα-ecdysoneorβ-ecdysone.Changingtheosmoticpressureoftheβ-ecdysonecontainingmediumlikewisedidnotalterthenoxiouseffectofβ-ecdysone.Discsculturedfirstinthepresenceofβ-ecdysone(for24hr),thentransferredtofreshmediumcontainingα-ecdysonewereunabletoundergonormaldevelopment.Theinhibitoryeffectofβ-ecdysonethusappearstobeirreversible.Discsculturedfirstinthepresenceofα-ecdysone(for24,48or72hr),thentransferredtoβ-ecdysonecontainingmedium,wereunabletocontinuetheirnormaldifferentiation.Furtherdevelopmentwasblockedwithinafewhoursafterthetransfer.Resultsarediscussedinviewofresultsobtainedwithotherinvitroandinvivocultivationtechniques.Inconclusion,isolatedlegdiscsofDrosophilaareunabletorespondphysiologicallytoexogenousβ-ecdysone.Onlyα-ecdysoneandinokosteronewillinducecompleteandnormalmetamorphosisinlegdiscsculturedinvitro.

[学科分类] 生物科学（综合）