Phenotypic suppression of morphogenetic mutants of Dictyostelium discoideum☆

摘要

TheeffectsofcAMPpulsesonthecapacityof15aggregatelessmutantstodifferentiateandconstructfruitingbodiesarecomparedtothoseobtainedwhenmutantcellsarestarvedwithwild-typeamoebae.Mutantstrainsareclassifiedintothreemaingroupsdependinguponthedegreetowhichtheirphenotypicdefectscanbecorrected.Thesedataextendstudiespublishedearlier[Darmon,M.,Brachet,P.,andPereiradaSilva,L.(1975).ChemotacticsignalsinducecelldifferentiationinDictyosteliumdiscoideum.Proc.Nat.Acad.Sci.USA72,3163a€“3166;PereiradaSilva,L.,Darmon,M.,Brachet,P.,Klein,C.,andBarrand,P.(1975).InductionofcelldifferentiationbythechemotacticsignalinDictyosteliumdiscoideum.Ina€?ProceedingsoftheTenthFEBSMeeting,a€?pp.269a€“276].(1)OnlyonemutantwasunresponsivebothtocAMPpulsesandtothepresenceofwild-typeamoebaeanddidnotdisplayanyofthepropertiesofdifferentiatedcells.(2)FollowingtreatmentwithcAMPpulses,11mutantsdevelopedcertainpropertiesofaggregation-competentamoebae.Theyincreasedtheirlevelsofcellularphosphodiesterase,showedanenhancedchemotacticsensitivitytocAMP,andestablishedspecificcellcontacts.Noneoftheseamoebaecoulddifferentiatefurther.Theydidco-aggregatetosomeextentwithwild-typecells,butfailedtodifferentiateintospores.Rather,mutantcellswereexcludedfromthepseudoplasmodiumduringtheprocessofmorphogenesisofthefruitingbody.(3)Incontrast,theaggregatelessphenotypeofthreemutantswasfullycorrectedbybothcAMPpulsesandthepresenceofwild-typecells.Thesefindingsarediscussedonthebasisofarelationshipbetweenthechemotacticsignalandcelldifferentiation.