Publications by authors named "Ken-Ichi Nonomura"

Small RNAs are highly abundant and play important roles in plant reproduction. Profiling of small RNAs in reproductive tissues is a critical step in understanding their biology. Here, we describe a protocol for small RNA profiling in rice anthers, with a focus on an abundantly expressed but little-understood reproductive small RNA class named 24-nucleotide phased secondary small interfering RNAs (24-nt phasiRNAs).

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Fertilization relies on pollen mother cells able to transit from mitosis to meiosis to supply gametes. This process involves remarkable changes at the molecular, cellular and physiological levels including (but not limited to) remodelling of the cell wall. During the meiosis onset, cellulose content at the pollen mother cell walls gradually declines with the concurrent deposition of the polysaccharide callose in anther locules.

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Article Synopsis
  • In angiosperms, epigenetic profiles crucial for genomic imprinting are set up before fertilization, but the connection between these modifications and gene expression is not fully clear.
  • This research categorized imprinted genes in rice endosperm into 'persistent' and 'stage-specific' types based on a transcriptome analysis over time and found differences in the levels of epigenetic modifications between them.
  • The study showed that maternal allele activation in maternally expressed imprinted genes is linked to DNA demethylation, while paternally expressed genes with gene body methylation are silenced through similar processes and associated with specific genetic motifs.
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Cytoplasmic ribonucleoprotein (RNP) granules are membraneless structures composed of various RNAs and proteins that play important roles in post-transcriptional regulation. While RNP granules are known to regulate the meiotic entry in some organisms, little is known about their roles in plants. In this study, we observed the cytoplasmic granular structures of rice RNA-binding protein MEIOSIS ARRESTED AT LEPTOTENE2 (MEL2), which contributes to the control of meiotic entry timing, in leaf protoplasts and spore mother cells.

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Article Synopsis
  • Plant stems consist of nodes and internodes that have distinct functions for solute exchange and growth, yet their boundaries are unclear.
  • In rice, researchers discovered that specific genes help control node formation and promote internode development by inhibiting genes associated with leaf growth and other node features.
  • This study suggests that the organization of these gene groups is unique to seed plants and highlights the evolutionary divergence of nodes and internodes.
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The stem, consisting of nodes and internodes, is the shoot axis, which supports aboveground organs and connects them to roots. In contrast to other organs, developmental processes of the stem remain elusive, especially those initiating nodes and internodes. By introducing an intron into the Cre recombinase gene, we established a heat shock-inducible clonal analysis system in a single binary vector and applied it to the stem in the flag leaf phytomer of rice (Oryza sativa).

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Timely progression of the meiotic cell cycle and synchronized establishment of male meiosis in anthers are key to ascertaining plant fertility. With the discovery of novel regulators of the plant cell cycle, the mechanisms underlying meiosis initiation and progression appear to be more complex than previously thought, requiring the conjunctive action of cyclins, cyclin-dependent kinases, transcription factors, protein-protein interactions, and several signaling components. Broadly, cell cycle regulators can be classified into two categories in plants based on the nature of their mutational effects: (1) those that completely arrest cell cycle progression; and (2) those that affect the timing (delay or accelerate) or synchrony of cell cycle progression but somehow complete the division process.

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Callose is a plant cell wall polysaccharide whose deposition is spatiotemporally regulated in various developmental processes and environmental stress responses. The appearance of callose in premeiotic anthers is a prominent histological hallmark for the onset of meiosis in flowering plants; however, the biological role of callose in meiosis remains unknown. Here, we show that rice (Oryza sativa) GLUCAN SYNTHASE LIKE5 (OsGSL5), a callose synthase, localizes on the plasma membrane of pollen mother cells (PMCs) and is responsible for biogenesis of callose in anther locules through premeiotic and meiotic stages.

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In transgenic experiments, we often face fundamental requirements such as overexpressing a certain gene, developing organelle markers, testing promoter activities, introducing large genomic fragments, and combinations of them. To fulfill these multiple requirements in rice, we developed simple binary vectors with or without maize () promoter, Gateway cassette and fluorescent proteins. First, we compared stabilities of cauliflower mosaic virus and maize promoters for constitutive gene expression in transgenic rice.

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Transposable elements (TEs) constitute a large proportion of genomes of multicellular eukaryotes, including flowering plants. TEs are normally maintained in a silenced state and their transpositions rarely occur. Hybridization between distant species has been regarded as a 'shock' that stimulates genome reorganization, including TE mobilization.

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Asian rice ( L.) is consumed by more than half of the world's population. Despite its global importance, the process of early rice domestication remains unclear.

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The development of floral organs is coordinated by an elaborate network of homeotic genes, and gibberellin (GA) signaling is involved in floral organ development; however, the underlying molecular mechanisms remain elusive. In the present study, we found that MOS4-ASSOCIATED COMPLEX 5A (MAC5A), which is a protein containing an RNA-binding motif, was involved in the development of sepals, petals, and stamens; either the loss or gain of function resulted in stamen malformation and a reduced seed set. The exogenous application of GA considerably exacerbated the defects in null mutants, including fewer stamens and male sterility.

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Proper anther and pollen development are important for plant reproduction. The plant hormone gibberellin is important for anther development in rice, but its gametophytic functions remain largely unknown. Here, we report the functional and evolutionary analyses of rice gibberellin 3-oxidase 1 (OsGA3ox1), a gibberellin synthetic enzyme specifically expressed in the late developmental stages of anthers.

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Biological resources are the basic infrastructure of bioscience research. Rice ( L.) is a good experimental model for research in cereal crops and monocots and includes important genetic materials used in breeding.

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In angiosperms, endosperm development comprises a series of developmental transitions controlled by genetic and epigenetic mechanisms that are initiated after double fertilization. Polycomb repressive complex 2 (PRC2) is a key component of these mechanisms that mediate histone H3 lysine 27 trimethylation (H3K27me3); the action of PRC2 is well described in Arabidopsis thaliana but remains uncertain in cereals. In this study, we demonstrate that mutation of the rice (Oryza sativa) gene EMBRYONIC FLOWER2a (OsEMF2a), encoding a zinc-finger containing component of PRC2, causes an autonomous endosperm phenotype involving proliferation of the central cell nuclei with separate cytoplasmic domains, even in the absence of fertilization.

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Reproduction-specific small RNAs are vital regulators of germline development in animals and plants. MicroRNA2118 (miR2118) is conserved in plants and induces the production of phased small interfering RNAs (phasiRNAs). To reveal the biological functions of miR2118, we describe here rice mutants with large deletions of the miR2118 cluster.

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Genetic transformation is one of the most important technologies for revealing or modulating gene function. It is used widely in both functional genomics and molecular breeding of rice. Demands on its use in wild Oryza species is increasing because of their high genetic diversity.

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Autophagy has recently been shown to be required for tapetal programmed cell death (PCD) and pollen maturation in rice. A transcriptional regulatory network is also known to play a key role in the progression of tapetal PCD. However, the relationship between the gene regulatory network and autophagy in rice anther development is mostly unknown.

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The Oryza officinalis complex is the largest species group in Oryza, with more than nine species from four continents, and is a tertiary gene pool that can be exploited in breeding programs for the improvement of cultivated rice. Most diploid and tetraploid members of this group have a C genome. Using a new reference C genome for the diploid species O.

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Autophagy plays crucial roles in the recycling of metabolites, and is involved in many developmental processes. Rice mutants defective in autophagy are male sterile due to immature pollens, indicating its critical role in pollen development. However, physiological roles of autophagy during seed maturation had remained unknown.

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We have previously shown that autophagy is required for post meiotic anther development including programmed cell death-mediated degradation of the tapetum and pollen maturation in rice. However, the spatiotemporal dynamics of autophagy in the tapetum remain poorly understood. We here established an in vivo imaging technique to analyze the dynamics of autophagy in rice tapetum cells by expressing green fluorescent protein-tagged AtATG8, a marker for autophagosomes.

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The 24-nucleotides (nt) phased secondary small interfering RNA (phasiRNA) is a unique class of plant small RNAs abundantly expressed in monocot anthers at early meiosis. Previously, 44 intergenic regions were identified as the loci for longer precursor RNAs of 24-nt phasiRNAs (24-PHASs) in the rice genome. However, the regulatory mechanism that determines spatiotemporal expression of these RNAs has remained elusive.

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In angiosperms, germline precursors and germ cells are always attached to or engulfed within somatic companion cells until just before fertilization. This is because sperm and egg cells develop as part of the multicellular gametophyte. Thus, the non-cell-autonomous regulation by somatic companions plays important roles in efficient reproduction, in addition to the cell-autonomous regulation.

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