Narie Sasaki

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For more than 140 years, pollen tube guidance in flowering plants has been thought to be mediated by chemoattractants derived from target ovules. However, there has been no convincing evidence of any particular molecule being the true attractant that actually controls the navigation of pollen tubes towards ovules. Emerging data indicate that two synergid(More)
In flowering plants, guidance of the pollen tube to the embryo sac (the haploid female gametophyte) is critical for successful fertilization. The target embryo sac may attract the pollen tube as the final step of guidance in the pistil. We show by laser cell ablation that two synergid cells adjacent to the egg cell attract the pollen tube. A single synergid(More)
Flowering plants have evolved a unique reproductive process called double fertilization, whereby two dimorphic female gametes are fertilized by two immotile sperm cells conveyed by the pollen tube. The two sperm cells are arranged in tandem with a leading pollen tube nucleus to form the male germ unit and are placed under the same genetic controls. Genes(More)
The complete sequence of the mitochondrial DNA (mtDNA) of the true slime mold Physarum polycephalum has been determined. The mtDNA is a circular 62,862-bp molecule with an A+T content of 74.1%. A search with the program BLAST X identified the protein-coding regions. The mitochondrial genome of P. polycephalum was predicted to contain genes coding for 12(More)
The synergid cell of Torenia fournieri attracts pollen tubes by a diffusible but yet unknown chemical attractant. Here we investigated the species difference of the attractant using five closely related species in two genera, namely T. fournieri, Torenia baillonii, Torenia concolor, Lindernia (Vandellia) crustacea, and Lindernia micrantha. These five(More)
Mitochondrial transcription factor A (TFAM), a transcription factor for mitochondrial DNA (mtDNA) that also possesses the property of nonspecific DNA binding, is essential for maintenance of mtDNA. To clarify the role of TFAM, we repressed the expression of endogenous TFAM in HeLa cells by RNA interference. The amount of TFAM decreased maximally to about(More)
Chloroplast DNA (cpDNA) is packed into discrete structures called chloroplast nucleoids (cp-nucleoids). The structure of cpDNA is thought to be important for its maintenance and regulation. In bacteria and mitochondria, histone-like proteins (such as HU and Abf2, respectively) are abundant and play important roles in DNA organization. However, a primary(More)
Telomerase is active in immature somatic cells, but not in differentiated cells. However, the regulation during cell differentiation is not well understood. In this study, a human chronic myelogenous leukemia cell line (K562) was induced to differentiate into megakaryocytes by TPA, and erythroid by STI571. A human acute myeloblastic leukemia cell line(More)
Mammalian cells typically contain thousands of copies of mitochondrial DNA assembled into hundreds of nucleoids. Here we analyzed the dynamic features of nucleoids in terms of mitochondrial membrane dynamics involving balanced fusion and fission. In mitochondrial fission GTPase dynamin-related protein (Drp1)-deficient cells, nucleoids were enlarged by their(More)