Showing papers by "Shigeyuki Kawano published in 2001"
TL;DR: Dioecious plants have unisexual flowers, which have stamens or pistils, which are caused by the suppression of opposite sex primordia, and sex chromosome linkage in these plants suggests that female suppressor and stamen promoter genes are localized on the Y chromosome.
Abstract: Sex chromosomes have been reported in several dioecious plants. The most general system of sex determination with sex chromosomes is the XY system, in which males are the heterogametic sex and females are homogametic. Genetic systems in sex determination are divided into two classes including an X chromosome counting system and an active Y chromosome system. Dioecious plants have unisexual flowers, which have stamens or pistils. The development of unisexual flowers is caused by the suppression of opposite sex primordia. The expression of floral organ identity genes is different between male and female flower primordia. However, these floral organ identity genes show no evidence of sex chromosome linkage. The Y chromosome of Rumex acetosa contains Y chromosome-specific repetitive sequences, whereas the Y chromosome of Silene latifolia has not accumulated chromosome-specific repetitive sequences. The different degree of Y chromosome degeneration may reflect on evolutionary time since the origination of dioecy. The Y chromosome of S. latifolia functions in suppression of female development and initiation and completion of anther development. Analyses of mutants suggested that female suppressor and stamen promoter genes are localized on the Y chromosome. Recently, some sex chromosome-linked genes were isolated from flower buds of S. latifolia.
79 citations
TL;DR: The complete sequence of the mitochondrial DNA of the true slime mold Physarum polycephalum has been determined and it was suggested that sites of RNA editing vary among strains.
Abstract: The complete sequence of the mitochondrial DNA (mtDNA) of the true slime mold Physarun 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 known proteins [for three cytochrome c oxidase subunits, apocytochrome b, two F1Fo-ATPase subunits, five NADH dehydrogenase (nad) subunits, and one ribosomal protein], two rRNA genes, and five tRNA genes. However, the predicted ORFs are not all in the same frame, because mitochondrial RNA in P. polycephalum undergoes RNA editing to produce functional RNAs. The nucleotide sequence of an nad7 cDNA showed that 51 nucleotides were inserted at 46 sites in the mRNA. No guide RNA-like sequences were observed in the mtDNA of P. polycephalum. Comparison with reported Physarum mtDNA sequences suggested that sites of RNA editing vary among strains. In the Physarum mtDNA, 20 ORFs of over 300 nucleotides were found and ORFs 14 19 are transcribed.
64 citations
TL;DR: Phylogenetic analyses of partial actin gene sequences suggest that autosporulation is the ancestral mode of cell division in Nannochloris species, which seems to be among the smallest for free‐living eukaryotes.
Abstract: A single cell divides to multiply, but not all cells follow the same pattern of division. We studied cell division in seven strains from six species belonging to the genus Nannochloris Naumann and classified their modes of cell division into three types: binary fission (N. bacillaris Naumann), budding (N. coccoides Naumann), and autosporulation resulting in the formation of two to four daughter cells (N. maculata Butcher, N. sp. SAG 251-2, N. atomus Butcher CCAP 251/7 and SAG 14.87, and N. eucaryotum[Wilhelm et al.] Menzel and Wild). To determine the evolutionary relationships among these multiple modes of cell division, we investigated the strains' genome sizes, copy number of actin genes, and phylogeny. The genome sizes were determined by counter-clamped homogeneous electric fields electrophoresis and fluorimetry. The genomes are very small and range from 12.6 Mbp (N. maculata) to 47.4 Mbp (N. atomus SAG 14.87). The genomes of Nannochloris species seem to be among the smallest for free-living eukaryotes. Nannochloris bacillaris (binary fission), N. coccoides (budding), Nannochloris sp. (two-cell type of autosporulation), and N. eucaryotum (multicell type of autosporulation) contain a single actin gene, whereas N. maculata (two-cell type of autosporulation) and two strains of N. atomus (two-cell type of autosporulation) contain two actin genes. This suggests that the actin gene was duplicated in this eukaryote, which has a very small genome. Phylogenetic analyses of partial actin gene sequences suggest that autosporulation is the ancestral mode of cell division.
38 citations
TL;DR: Transfer of stationary-phase cultured tobacco cells into auxin-depleted culture medium induces amyloplast formation and the expression of at least one isoform of SBE is regulated differently from theexpression of AgpS and GBSS at the transcriptional or post-transcriptional level, suggesting at leastone de novo synthesized protein is required in order to control the expression.
11 citations