Changes in the polyadenylated messenger RNA population during development of Dictyostelium discoideum☆

[摘要] TheprogramofgeneexpressionduringthelifecycleofDictyosteliumdiscoideumhasbeenassessedbymolecularhybridizationofcDNAprobeswithpolysomalRNAextractedatthefollowingdifferentstagesofdevelopment:vegetativegrowth,interphase(2.5hr),aggregation(8hr),postaggregation(12hr),andpreculmination(18hr).SeveraldifferentcDNAprobeswereused.Twoprobeswerepreparedfromvegetativestagepoly(A+)RNA,onerepresentingallspeciespresentandtheotherenrichedforabundantspecies.AthirdcDNAprobewaspreparedfrompreculminationstagepolysomalRNAandafourthprobeconsistedofthepreculminationstagecDNAdepletedinthosespeciesalsopresentatthevegetativestage.HybridizationofthevariousprobeswiththedifferentpolysomalRNApreparationshasrevealeddevelopmentalchangesinthemRNApopulations.Thesechangeswerenotdetectedinanaggregationlessmutantundersimilarconditionsofstarvation.AbundantRNAspeciesofvegetativecellswerefoundtodroptolowlevels,especiallyduringtheaggregationperiod.FiftypercentbymassoftheRNApresentinpolysomesat18hrisnotpresentduringvegetativegrowth.SomeofthenewRNAspeciesappearedduringinterphaseandtheremainingduringthepostaggregationperiod.AgradualincreaseinthenumberofcopiespercellofcertainRNAspeciescomprisingbothnewspeciesaswellassomesharedwithvegetativecellswasobservedthroughoutdevelopment.OtherresultsindicatedthatthecompositionofpolysomalandcytoplasmicRNAissimilarduringvegetativegrowthbutdiffersmarkedlyat18hrofdevelopment.Also,cytoplasmicRNAat18hrcontained,inadditiontopolysomalRNA,alargeproportionbymassofnonpolysomalRNAsimilartovegetativeRNA.ThenumberofpolysomalRNAspeciesdetectedbythisanalysisduringvegetativegrowthandduringthepreculminationstagewereestimatedtobe3000and3700,respectively.ThenumberofcopiesoftheseRNAspeciesrangedbetween30and2000percellduringvegetativegrowthand3to300percellinpolysomesat18hr.DevelopmentallyinducedRNAswhichwerepreferentiallydistributedamongabundantandintermediateclasseswereestimatedtonumber700–900species.

[学科分类] 生物科学（综合）