Macronuclear development and gene expression in the exconjugants of Paramecium caudatum

摘要

PostzygoticnucleiaredeterminedtobemacronuclearanlagenimmediatelyafterthethirddivisionofthefertilizationnucleusinParameciumcaudatum.Soonafterdetermination,chromaticaggregatesappearintheanlagen.MicrospectrophotometryrevealedthatamarkedincreaseintheDNAcontentofmacronuclearanlageoccurredafterdisintegrationofthechromaticaggregates,about18hrafternucleardetermination.Thephenotypicexpressionoffivegeneswasinvestigatedduringthedevelopmentalprocess;+tnd-1,+tnd-2,+cnrA,+cnrB,and+cnrD.Thephenotypicexpressionof+tnd-1beganabout18hrafternucleardeterminationandof+cnrBatabout24hrat27?°C.However,phenotypicexpressionofthethreeothergenesbeganabout40hrafterdetermination.ItcanbeconcludedthatsomeofthegenesofmacronuclearanlagenbegintobeexpressedatorbeforethefirstmeasurableincreaseintheamountofDNAoftheanlagen.