Papers by Masaki Shimamura
Plant morphology, 2023
Cyanobacteria and many eukaryotic algae have a carbon-concentrating mechanism (CCM) within each c... more Cyanobacteria and many eukaryotic algae have a carbon-concentrating mechanism (CCM) within each cell or individual chloroplast to enable efficient photosynthesis even in CO 2 -deficient environments. The 'pyrenoids', a chloroplast internal compartment responsible for CCM in eukaryotic algae, are absent in chloroplasts of land plants, and CCM at the cellular level appears to have been lost during the evolution of land plants. However, only hornworts have pyrenoids in their chloroplasts and are believed to possess CCM. This review summarizes the current status of research on the characteristics and functions of pyrenoids in hornworts and their evolutionary origin, and discusses why hornworts are the only land plants that possess pyrenoids.
Taxonomic reevaluation of the Japanese Marchantia taxa belonging to sect. Papillatae of subg. Chlamidium (Marchantiaceae)
The Bryologist
Abstract. The Japanese Marchantia taxa belonging to sect. Papillatae of subg. Chlamidium have bee... more Abstract. The Japanese Marchantia taxa belonging to sect. Papillatae of subg. Chlamidium have been taxonomically ambiguous for a long time because many species and infraspecific taxa have been described based on their broad morphological variation. In order to resolve this taxonomic problem, nearly 200 specimens including type material of names placed in the section were morphologically examined. Among them, 45 specimens collected during our recent field work in Japan were newly sequenced for phylogenetic analysis. The molecular analysis showed that Japanese plants belonging to sect. Papillatae should be partitioned into two distinct clades. The plants belonging to the two clades were distinguishable by the presence or absence of a dark median band on the thallus and the morphology of the appendage of ventral scales and gametangiophores. Geographic distribution and ecological habitats in Japan also support the partitioning into two distinct clades. We propose the new combination M. emarginata subsp. cuneiloba (≡ M. cuneiloba). We also suggest that M. emarginata subsp. cuneiloba and M. papillata subsp. grossibarba are the appropriate names for the plants belonging to each clade. The species previously described from Japan (e.g., M. radiata Horik., M. tosana Steph. and M. tosayamensis Steph.) were synonymized for both of them.
Behavior of plastid and plastid DNA during spermiogenesis in Dumortiera hirsuta
Bryological Research, 1999
Diversity and evolution of cell division system in land plants
Kenbikyo, 2005
A hepatic species of Sphaerocarpos (Sphaerocarpaceae) newly found in Japan
Bryological Research, 2012
The complete chloroplast genome of Petasites japonicus (Siebold Zucc.) Maxim. (Asteraceae)
Mitochondrial DNA Part B, 2021
Abstract The complete chloroplast (cp) genome sequence of Petasites japonicus (Asteraceae) was de... more Abstract The complete chloroplast (cp) genome sequence of Petasites japonicus (Asteraceae) was determined. The cp genome is 150,445 bp and consists of a large single-copy region (82,910 bp), a small single-copy region (17,907 bp), and a pair of inverted repeats (24,814 bp). It encodes a set of 114 genes, consisting of 80 protein-coding genes, 30 tRNA genes, and four rRNA genes. Phylogenetic inference confirmed that P. japonicus is sister to the genus Ligularia in the tribe Senecioneae of Asteraceae.
The phylogenetic data supporting the segregation of Marchantia paleacea species complex into sub-species level
Morphology of gemmae, an overlooked taxonomic trait in the genus Marchantia L. (Marchantiaceae)
The Bryologist, 2020
Abstract. Most taxa of the genus Marchantia L. (Marchantiaceae) produce multicellular gemmae with... more Abstract. Most taxa of the genus Marchantia L. (Marchantiaceae) produce multicellular gemmae within gemma cups. They are discoid bodies with two notches and a trace of stalk. Although gemmae of Marchantia have been of interest to physiological and developmental studies, they have been rarely used as a taxonomic character. To improve understanding of the taxonomic significance of gemma morphology, we investigated gemmae of six Japanese Marchantia (including four subspecies) and provide comparative morphological descriptions and a key. Several characters of the gemmae, including size, shape, morphology of marginal cells, and the presence or absence of mucilage hairs were useful in species identification. Morphological similarity of gemmae between M. polymoprpha and M. paleacea, as well as between M. emarginata and M. pinnata, was consistent with the results of molecular phylogenetic analyses. We recommend that morphology of gemmae should be used as a new taxonomic character in the genus Marchantia.
Current Biology, 2019
Highlights d Loss of miR529c causes gamete production in the absence of environmental signals d R... more Highlights d Loss of miR529c causes gamete production in the absence of environmental signals d Repression of MpSPL2 expression by miR529c prevents the reproductive transition d MpSPL2 is involved in, but not essential for, reproductive development d The miR156/529-SPL module controls the reproductive transition in land plants Authors
Plant & cell physiology, 2016
One of the classical research plants in plant biology, Marchantia polymorpha, is drawing attentio... more One of the classical research plants in plant biology, Marchantia polymorpha, is drawing attention as a new model system. Its ease of genetic transformation and a genome sequencing project have attracted attention to the species. Here I present a thorough assessment of the taxonomic status, anatomy and developmental morphology of each organ and tissue of the gametophyte and sporophyte on the basis of a thorough review of the literature and my own observations. Marchantia polymorpha has been a subject of intensive study for nearly 200 years, and the information summarized here offers an invaluable resource for future studies on this model plant.
DIVISION PLANE ORIENTATION IN MEIOSIS OF Conocepharum japonicum THAT PRODUCES LINEAR TETRADS
Cytokinetic apparatus in land plants and the evolution of multicellular body on land
Gamma-tubulin distribution during meiosis of Dumortiera hirsuta (Bryopyta)
GAMMA.-tubulin localization in spermatogenesis of liverworts
Comparative morphological study on the apical cell in hepatics
The equal segregation of plastids between daughter cells at cell division in apical meristem of tobacco
Pre-meiotic microtubule system associated with plastid partitioning in polyplastidic meiosis of liverworts (Bryophyta)
Andreaea nivalis and Takakia lepidozioides found in Mt. Norikura, Gifu Prefecture, central Japan(Threatened Bryophytes in Japan)
Bryological Research, 2008
Microtubule organization and plastid distribution during meiosis of Haplomitrium mnioides (Haplomitriopsida)
Bryophyte Diversity and Evolution
The organization of microtubules and plastid distribution of the liverwort, Haplomitrium mnioides... more The organization of microtubules and plastid distribution of the liverwort, Haplomitrium mnioides (Haplomitriopsida), was studied during the meiotic phase lasting for six months. In the late fall, the cytoplasm of early sporocytes forms four lobes of future spore domains before meiotic prophase. Microtubules align at the cytoplasmic cleavage furrow regions as girdling bands in the four-lobed sporocytes. Finally, the cleavage furrows are proximal to the nucleus positioned in the center of the sporocyte, and the girdling bands of the microtubule (GBM) disappear. Subsequently, the nucleus moves into one of the cytoplasmic lobes, and sporocytes pass the winter season at this stage. In early spring, the nucleus returns to the central position of the lobed cytoplasm, concurrent with plastid repositioning around the nucleus. Plastids are then distributed equally to each of the four lobes as a plastid cluster. Astral microtubules emanate from the plastid cluster in each spore domain and enc...
Microtubule Organizing Centers on the Plastid and Nuclear Surface of Bryophytes
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Papers by Masaki Shimamura