Ref ID : 7374
Miwa Isoji, Izumo Tatsuo, and Sonoda Tomoko; Cytoplasm Rescues an Arrhythmic Mutant on the Circadian Rhythm of Mating Reactivity in Paramecium bursaria. J.Eukaryot.Microbiol. 43(3):231-236, 1996
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Cells of an unusual Paramecium bursaria stock (Sj2) expressed rhythmic mating reactivity in a light/dark cycle (LD) and under continuous illumination (LL). When placed in continuous darkness (DD), did not show rhythmicity but rather demonstrated a continuous high mating reactivity. However, mating reactivity was reduced following exposure to a 6-hr light pulse interrupting the DD, and then recovered to its former condition. Genetic analysis showed the arrhythmicity in DD to be a dominant character inherited in a Mendelian ratio. On the other hand, a clone (MC1w) that did not show the rhythmicity in either DD or LL was isolated from the parent stock Sj2w following a 5-hr treatment with 2 µg/ml nitrosoguanidine (MNNG). The MC1w cells expressed weak rhythmicity in LD, but were insensitive to a 6-hr light pulse in DD. The arrhythmicity in LL was inherited cytoplasmically. In addition to this, rhythmicity in LL could be recovered by injection of cytoplasm from the wild-type cell when the recipient cell was homozygous for the wild-type nuclear gene (+/+). The cytoplasmic components or factors are assumed to control the functional circadian system and genetically determine the rhythmicity of mating reactivity.