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Phenotypic and genetic analysis of "Chameleon," a paramecium mutant with an enhanced sensitivity to magnesium
Journal article   Open access   Peer reviewed

Phenotypic and genetic analysis of "Chameleon," a paramecium mutant with an enhanced sensitivity to magnesium

Robin Preston and Jocelyn Hammond
Genetics (Austin), v 146(3), pp 871-880
01 Jul 1997
DOI: https://doi.org/10.1093/genetics/146.3.871
PMID: 9215893
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https://doi.org/10.1093/genetics/146.3.871View
Published, Version of Record (VoR)Maybe Open Access (Publisher Bronze),  Open

Abstract

Genetics Mutation
Three mutant strains of Paramecium tetraurelia with an enhanced sensitivity to magnesium have been isolated. These new "Chameleon" mutants result from partial- or codominant mutations at a single locus, Cha. Whereas the wild type responded to 5 mM Mg2+ by swimming backward for 10-15 sec, Cha mutants responded with approximately 30 sec backward swimming. Electrophysiological analysis suggested that this behavior may be caused by slowing in the rate at which a Mg(2+)-specific ion conductance deactivates following membrane excitation. This would be consistent with an observed increase in the sensitivity of Cha mutants to nickel poisoning, since Ni2+ is also able to enter the cell via this pathway. More extensive behavioral analysis showed that Cha cells also overresponded to Na+, but there was no evidence for a defect in intracellular Ca2+ homeostasis that might account for a simultaneous enhancement of both the Mg2+ and Na+ conductances. The possibility that the Cha locus may encode a specific regulator of the Mg(2+)- and Na(+)-permeabilities is considered.

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