Identification of two nickel ion-induced genes, NCI16 and PcGST1, in Paramecium caudatum

Immaturin-Nuclease as a Model System for a Gene-Programmed Sexual Development and Rejuvenescence in Paramecium Life History

Fertilization-initiated development and adult-onset aging are standard features in the life history of eukaryotes. In Paramecium, the number of cell divisions after the birth of a new generation is an essential parameter of sexual phase transition and aging. However, the gene driving this process and its evolutionary origin have not yet been elucidated. Here we report several critical outcomes obtained by molecular genetics, immunofluorescence microscopy, transformation by microinjection, and enzymological analysis. The cloned immaturin gene induces sexual rejuvenation in both mature and senescent cells by microinjection. The immaturin gene originated from proteobacteria's glutathione-S-transferase (GST) gene. However, immaturin has been shown to lose GST activity and instead acquire nuclease activity. In vitro substrates for immaturin-nuclease are single- and double-stranded DNA, linear and circular DNA, and single-stranded viral genome RNA such as coronavirus. Anti-immaturin antibodies have shown that the subcellular localizations of immaturin are the macronucleus, cytoplasm, cell surface area, and cilia. The phase transition of sexuality is related to a decrease in the intracellular abundance of immaturin. We propose that sexual maturation and rejuvenation is a process programmed by the immaturin gene, and the sexual function of each age is defined by both the abundance and the intracellular localization mode of the immaturin-nuclease.

Micromanipulation in Paramecium: From Non-Mendelian Inheritance to the Outlook for Versatile Micromachines

This review addresses nine areas of knowledge revealed by micromanipulations performed with Paramecium. Microinjection has shown that sexual maturation and senescence of Paramecium caudatum is a programmed process conducted by a specific gene and its product protein. In Paramecium tetraurelia, autogamy was revealed to depend on the number of DNA syntheses rather than the number of cell divisions in clonal aging. The cytoplasmic complementarity test established that microinjection of wild‐type cytoplasm can correct genetic defects of mutants. The concept of complementarity together with protein chemistry revealed compounds that control membrane excitability. In non‐Mendelian inheritance, noncoding small RNAs made from the parental micronucleus regulate the rearrangement of the progeny's macronuclear DNA. The macronucleus has the potential to be used as a factory for genetic engineering. The development and differentiation of progeny's nuclei in mating pairs are controlled by the parental macronucleus. The chemical reaction processes associated with exocytosis have been revealed by microinjection of various enzymes and antibodies. Using the fusion gene of histone H2B and yellow‐fluorescence protein, it was revealed that the fusion gene‐mRNA is transferred between cells during mating. Experiments with endosymbiotic bacteria and the host shed light on the conditions needed to establish sustainable symbiotic relationships.