Cytoplasm rescues an arrhythmic mutant on the circadian rhythm of mating reactivity in Paramecium bursaria.
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-h 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-h treatment with 2 micrograms/ml nitrosoguanidine (MNNG). The MC1w cells expressed weak rhythmicity in LD, but were insensitive to a 6-h 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.
Miwa
I
I
Biological Laboratory, College of General Education, Ibaraki University, Japan.
Izumo
T
T
Sonoda
T
T
D000818:Animals; D002455:Cell Division / Q000235:genetics / Q000502:physiology; D002940:Circadian Rhythm / Q000235:genetics*; D003593:Cytoplasm; D005111:Extrachromosomal Inheritance; D009154:Mutation; D010247:Paramecium / Q000235:genetics* / Q000502:physiology