Demonstrates the connection between photosynthetic products and mating reactivity rhythms in mutant Paramecium bursaria, suggesting significant implications for circadian biology.
Paramecium bursaria shows many kinds of circadian rhythms, including a mating reactivity rhythm. P. bursaria cells normally contain several hundred Chlorella in the cytoplasm as endosymbionts. We found an interesting mutant strain (Ok2) from nature. Chlorella-contain green cells (Ok2) showed a normal mating reactivity rhythm in a constant light condition (LL) or constant darkness (DD). However, Chlorella-free white cells (Ok2w) derived from Ok2 did not display a mating reactivity rhythm in LL. In DD, they showed a normal mating reactivity rhythm. When Ok2w cells were infected with Chlorella isolated from green cells that show normal mating reactivity rhythms, they exhibited a circadian mating rhythm in LL. The green Ok2 cells reverted to the non-reactive state in LL by treatment with the herbicide paraquat. Sugar components in the cytosol of Ok2 and Ok2w were analyzed by HPLC, and four kinds of sugars were identified in Ok2 cells of day time. When maltose and maltotriose were added to Ok2w cell culture, the mating reactivity rhythms appeared in white cells in LL. These results suggest that the photosynthetic products of symbiotic Chlorella are closely related to the expression of circadian rhythms in a mutant strain of P. bursaria.
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TANAKA, Miho / MIWA, Isoji (2000) studied this question.
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