Costimulation-Induced Rounding in Tetrahymena thermophila: Early Cell Shape Transformation Induced by Sexual Cell-to-Cell Collisions between Complementary Mating Types

摘要

MixingofstarvedcellsofcomplementarymatingtypesofTetrahymenathermophiliainducesshorteningoftheirlongitudinallengthwithin10minofmixing.Thisearlymorphogenetictransformationinpreconjugantsexualinteraction(costimulationperiod)wasnamed"costimulation-inducedrounding"(CIR).CIRistheearliestmorphologicalchangethathaseverbeenfoundinthecostimulationperiodanddiffersfrom"synchronousrounding"inthevegetativecellcycle,becauseCIRcellsarestillabletoformfoodvacuoles,whilecellsinsynchronousroundingdonothavethisability.Whensexualcell-to-cellcollisionsbetweentwomatingtypeswerehamperedbyunidirectionalstirringfor20minaftermixingofthetwomatingtypes,bothCIRandconjugationweredelayedby20min.Whensecretedmaterialsneededfortheonsetofcostimulationwereremovedbywashingthecellswith10mMTris-HCl,pH7.4,beforemixingthetwomatingtypes,bothCIRandconjugationweredelayedbyabout30min.CIR-likeroundingwasnotinducedbycell-freemediumeitherfromtheoppositematingtypeorfrommixedcostimulatedcells.TheseresultsindicatethatCIRisinducedwhencellsareactivatedtoformconjugatingpairsbycell-to-cellcollisionsbetweencomplementarymatingtypesinthepresenceofsecretedmolecules.