The cell cycle and its relationship to development in Dictyostelium discoideum
[摘要] WhendeprivedofexogenousnutrientssomeamoebasofDictyosteliumdiscoideumdocontinuetoprogressthroughthecellcycle.Therearetwodistinctperiodswhenmitoticcelldivisionoccurs.Labelingstudiesshowthatduringthefirstperiod,whichbeginsattheonsetofdevelopmentandceasesatthefirstvisiblesignsofaggregation(rippling),onlythosecellswhicharebeyondacertainpointinG2attheinitiationofdevelopmentdivide.Thesecondperiodofmitoticactivitybeginsattipformation,reachesmaximumactivityatthegrexstage,andceasesduringearlyculmination.Significantly,examinationofthedevelopmentofamoebasharvestedwheninthestationaryphaseofgrowth(andthusarrestedinG2)showsthatthesecellsstillundergomitoticcelldivisionduringthesecondperiodbutdonotshowanysuchdivisionduringthepreaggregationphase.Theextenttowhichincreasesincellnumbercanbetakentobeindicativeofmitoticcelldivisionvariesfromoneculturetoanotherduetothepresenceofvariablenumbersofmultinucleatecellswhichbecomemononucleateduringthefirst10hrofdevelopment.However,whendueallowancehasbeenmadefortheexistenceofthesecellsinaxenicallygrowingamoebalpopulations,ourdatashowthatbycompletionoffruitingbodyconstructiontherehasbeenadoublingincellnumberasadirectresultofmitoticcelldivision.NuclearDNAsynthesisalsooccursattwodistinctperiodsduringdevelopment,thesecoincidingwiththeperiodsofmitoticactivity.However,sincenomorethan35%ofthecellshaveundergonenuclearDNAsynthesisbytheendofthedevelopmentalphase,ourresultsareinconsistentwiththeconclusionthatallcellsaccumulateatapositioninG2atthetimeofaggregation.Ourresultsdosuggest,however,thatmitoticcelldivisionofafractionofthecellsmaybeanintegralpartofthedevelopmentalphase.
[发布日期] [发布机构]
[效力级别] [学科分类] 生物科学（综合）
[关键词] [时效性]
