New mutants of Paramecium tetraurelia defective in a calcium control mechanism: genetic and behavioral characterizations.
The k-shy mutants of Paramecium tetraurelia are altered in several Ca2+-dependent functions which regulate ciliary motility. The isolation, genetics, and phenotypes of these mutants are described. Of six independent isolates, all contained recessive single-factor mutations and comprise two unlinked loci, ksA and ksB. All k-shy strains showed prolonged backward swimming responses to depolarizing stimuli, but gave infrequent responses to some stimuli. At least four k-shy strains displayed temperature sensitivity. Neither ksA nor ksB was allelic or linked to dancer, a mutation causing weak Ca2+ current inactivation and prolonged backward swimming. Analysis of ks+; Dn double mutants revealed synergism between the two mutations. The ksA mutant survived Ba2+ solutions longer than wild type, but was more sensitive to K+. Together with previous studies, these results are consistent with a defect in reducing intracellular Ca2+ causing both prolonged ciliary reversal and reduced Ca2+ channel activity due to more active Ca2+-dependent feedback mechanisms. The integration of the Ca2+-dependent stimulatory and inhibitory functions is therefore dependent on ks+ gene functions. The ksA mutant was rescued by microinjection of wild-type cytoplasm, suggesting a possible behavioral assay for factors related to the ksA+ gene product.
Evans
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TC
Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin, Madison 53706.
Nelson
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DL
D000818:Animals; D001464:Barium / Q000494:pharmacology; D001522:Behavior, Animal; D002118:Calcium / Q000502:physiology*; D002470:Cell Survival / Q000187:drug effects; D002923:Cilia / Q000502:physiology*; D003433:Crosses, Genetic; D003593:Cytoplasm; D008564:Membrane Potentials; D008845:Microinjections; D009154:Mutation; D010247:Paramecium / Q000235:genetics*; D010641:Phenotype; D011188:Potassium / Q000494:pharmacology; D012641:Selection, Genetic; D013696:Temperature
D001464:Barium; D011188:Potassium; D002118:Calcium