研究者業績
基本情報
論文
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American Journal of Botany 2023年4月19日
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Urban Forestry & Urban Greening 79 127794-127794 2023年1月
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Heredity 126(5) 859-868 2021年 査読有りGeographic and environmental isolations of islands and the mainland offer excellent opportunity to investigate colonization and survival dynamics of island populations. We inferred and compared evolutionary processes and the demographic history of Rhododendron tsusiophyllum, in the Izu Islands and the much larger island Honshu, treated here as the mainland, using thousands of nuclear SNPs obtained by ddRAD-seq from eight populations of R. tsusiophyllum and three populations of R. tschonoskii as an outgroup. Phylogenetic relationships and their habitats suggest that R. tsusiophyllum had evolved and migrated from cold north to warm south regions. We detected clear genetic divergence among populations in three regions of Honshu and the Izu Islands, suggesting restricted migration between them due to isolated habitats on mountains even in the mainland. The three regions have different changes in effective population size, especially, genetic diversity and population size of the Izu Islands are small compared to the others. Further, habitats of populations in the Izu Islands are warmer than those in Honshu, suggesting that they have undergone adaptive evolution. Our study provides evidences of montane rather than insular isolation on genetic divergence, survival of populations and significance of adaptive evolution for island populations with small population size and low genetic diversity, despite close proximity to mainland populations.
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Tree Genetics & Genomes 17(3) 2021年 査読有り最終著者Plants growing in similar climates with extensively overlapping distributions may exhibit similar phylogeographic patterns, due to similarities in range shifts during past climatic oscillations. We tested and exploited this expectation in a comparison of the evolutionary and demographic histories of two related and co-distributed species endemic to Japan-Rhododendron pentaphyllum and R. quinquefolium. Genetic variation in sequences of noncoding chloroplast DNA regions and hundreds of nuclear single nucleotide polymorphisms were used to investigate 191 individuals from 13 populations of R. pentaphyllum and 142 individuals from 10 populations of R. quinquefolium. We found that the two species were not each other's closest relative, and we found different times to the most recent common ancestor of extant populations based on both chloroplast DNA and nuclear SNPs. Rhododendron pentaphyllum exhibited higher genetic variation between populations than R. quinquefolium, while the two species had similar patterns of genetic divergence between regions with slightly different divergence times. These lines of evidence suggest that the similar ranges of the two species are the result of repeated range shifts since speciation during climatic oscillations.
MISC
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日本森林学会大会学術講演集 127th 763-763 2016年種の多様化における原動力を解明することは、近年の生物地理学における課題の一つである。東アジアに固有なツツジ科ツツジ属ミツバツツジ節は、大陸辺縁部の島々に18の島固有種が分布する特徴を有する。それぞれの種は北海道から南西諸島・台湾に至る各地の多様なハビタットに生育するため、木本種の進化と適応放散を解明する上で適した材料であると考えられる。ミツバツツジ節の多様化は、葉緑体DNA塩基配列に基づく解析により第三紀末ごろから急速に進んだことが解明されている。本発表では対象種群の多様化の過程を中立進化の側面から明らかにすることを目的とした。そのために、次世代シークエンサーを用いたRADseq解析により大量配列情報を取得し、キャピラリーシークエンスにより葉緑体DNAの部分配列も決定した。本発表では、これらのデータを基に系統推定や個体群動態の推定を試みた結果を報告する。
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Natural History Research 7 (2) 101-105 2003年
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NEW PHYTOLOGIST 156(3) 417-426 2002年12月The cleavage of nuclear DNA into oligonucleosomal fragments that is the hallmark of apoptosis in animal cells occurs during the culture of Brassica napus leaf protoplasts. The changes in nuclei of cultured Brassica napus leaf protoplasts were studied by propidium iodide (PI) and 4', 6-diamino-2-phenylindole, dihydrochloride (DAPI) staining, transmission electron microscopy, flow cytometry analysis, and DNA laddering staining with ethidium bromide and Southern hybridization. Free 3'-OH termini of nuclear DNA fragments were labelled with DIG-dUTP, catalyzed by terminal deoxynucleotidyl transferase (TdT), and used as probes for Southern hybridization. This method (TUNEL on membrane) allowed visualization of DNA fragments with 3'-OH termini on a nylon membrane. These results suggest that loss of viability of protoplast with culture time is accompanied by apoptosis-like cell death. However, the forms or processes undergoing to apoptotic cell death in B. napus leaf protoplasts appears to be different in some details to those in animal cells.
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GRANA 39(6) 267-274 2000年Pollen wall development in Cryptomeria japonica was observed by scanning and transmission electron microscopy. The pollen of C japonica is characterized by a non-saccate, projecting papilla. The exine of C. japonica consists of the outer granular ectexine and the inner lamellated endexine. At the tetrad stage, the initial granular layer of the pro-ectexine first forms on the microspore plasma membrane. The tripartite lamellae of the pro-endexine form under the pro-ectexine. The prosporopollenin material is deposited on the pro-ectexine and pro-endexine at the free spore stage. The ectexine granule increases its volume and the endexine lamellae thicken. The papilla protrudes during the tetrad stage. The tip of the papilla bends laterally where the exine is thinner, Exine construction in C. japonica is similar to that of Cunninghamia; however, the amount and size of the granular ectexine and lamellated endexine differ. The conspicuous papilla protrudes and bends during the tetrad period.
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The Technical Bulletin of Faculty of Horticulture Chiba University 54 13-18 2000年
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The Technical Bulletin of Faculty of Horticulture Chiba University 53 19-28 1999年
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Plant Systematic and Evolution 201((1-4)) 1-14 1996年
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AMERICAN JOURNAL OF BOTANY 82(1) 75-80 1995年1月The arrangement of cortical microtubules (MTs) during spore formation in Equisetum arvense was examined by immunofluorescence microscopy. The arrangement of MTs was observed to change during sporoderm formation. During exospore formation, the cortical MTs of the tapetum appeared along the tapetal plasma membrane that enclosed each developing spore cell. After exospore formation, the arrangement of the cortical MTs changed into one of separate bands of MTs arranged spirally (spiral bands of MTs). The spiral bands of MTs were superimposed on the developing elaters. This new pattern corresponded to the pattern of cellulose microfibrils deposited in the inner layer of the elater, suggesting that these spiral bands are involved in the deposition of the cellulose microfibrils in the elater. We conclude that the spiral bands of MTs are functionally equivalent to cortical MTs in secondary wall formation.
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PROTOPLASMA 172(2-4) 145-153 1993年The arrangement of cortical microtubules during the development of the secondary wall and bordered pits in the tracheids of Taxus was examined by immunofluorescence and electron microscopy. The cambial region of radial longitudinal sections of developing young shoots (2-3 years old) contains cells at various stages of differentiation from cambial cells to tracheids. At the early stage of formation of bordered pits, circular bands of microtubules were seen to be associated with the inner edge of the border of the developing pit. In other regions than the pit secondary wall of uniform thickness was laid down, and obliquely oriented cortical microtubules ran parallel to one another. These cortical microtubules also covered the surface of the border of the developing pit on the side facing the center of the cell. As the border of the pit developed, a circular band of MTs remained associated with the inner edge of border, suggesting that the MTs were involved in the formation of the rim of the bordered pit, extending the initial border thickening, which consisted of concentrically oriented cellulose microfibrils. After completion of the formation of the bordered pit, helical thickenings became apparent. The obliquely oriented microtubules were organized in bands parallel to one another, being superimposed on the helical thickenings. The involvement of MTs in the formation of bordered pits and helical thickening is discussed.
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AMERICAN JOURNAL OF BOTANY 78(9) 1182-1190 1991年9月Spore wall morphogenesis of the microspore of Isoetes japonica was studied by transmission electron microscopy. The microspore wall consists of four layers: the perispore, outer exospore, inner exospore, and endospore. The perispore consists of electron-dense materials. The exospore is divided into outer and inner sections, with a large gap between the two. The outer exospore appears as a undulating plate consisting of tripartite lamellae with homogeneous sporopollenin. The inner exospore consists of an accumulation of tripartite lamellae on the microspore cell membrane. Immediately after meiosis, the tripartite lamellae of the outer exospore forms around the microspore. The lamellated inner exospore forms next, which adheres to the cell membrane of the microscpore. The deposition of homogeneous sporopollenin material on the tripartite lamellae causes the plates of the outer exospore to thicken. Some homogeneous material may also be deposited on the inner exospore. Lastly, the electron-dense perispore is deposited on the outer exospore, and the electron-lucent endospore forms beneath the inner exospore. We conclude that the lamellae of the outer exospore, inner exospore, and endospore are formed and derived, in that order, from the gametophytic microspore cytoplasm. The homogeneous sporopollenin material of the outer exospore and perispore may be derived from the sporophytic tapetal cytoplasm.
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GRANA 30(3-4) 597-600 1991年Pollen morphology of Andruris japonica (Triuridaceae) was investigated by light and electron microscopy. The pollen is monosulcate and has a size of 22-25-mu-m x 25-28-mu-m in polar view. In the non-apertural region the exine has gemmate to nearly verrucate protrusions of 0.4-0.5-mu-m in diameter and 0.3-0.5-mu-m in height, and a foot layer of 0.4-0.5-mu-m in thickness. The sporoderm of the apertural region has large gemmae of 0.7-0.8-mu-m in diameter and 0.6-0.7-mu-m in height, with a thin foot layer of 0.1-mu-m thickness.
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AMERICAN JOURNAL OF BOTANY 78(1) 24-36 1991年1月Spore wall morphogenesis of Lycopodium clavatum was observed by transmission electron microscopy. The spore plasma membrane indicates the reticulate spore sculpture shortly after meiosis. The mature spore wall of this species consists of two layers, inner endospore and outer exospore. There is no perispore in the sporoderm of this species. The exospore formation begins during the tetrad stage; and this layer is divided into two distinct sublayers, an outer lamellar layer and an inner granular layer. The lamellar layer is formed on the sculptured spore plasma membrane. Additional lamellae attach to this layer in a centripetal direction. For that reason, this layer may be derived from spore cytoplasm. The granular layer is formed only in the proximal region following lamellar layer formation, and it also may be derived from spore cytoplasm. The endospore is formed lastly and seems to be derived from spore cytoplasm as well. Accordingly, the spore sculpture of this species may be under the genetic control of the spore nucleus.
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BOTANICAL MAGAZINE-TOKYO 102(1067) 413-427 1989年9月
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AMERICAN JOURNAL OF BOTANY 76(7) 939-951 1989年7月
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Journal of Agricultural Science, Tokyo Nogyo Daigaku 33 1988年
書籍等出版物
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Pollen and Spores : Morphology and Biology 2000年
共同研究・競争的資金等の研究課題
24-
日本学術振興会 科学研究費助成事業 2024年4月 - 2028年3月
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日本学術振興会 科学研究費助成事業 2023年4月 - 2027年3月
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日本学術振興会 科学研究費助成事業 2023年4月 - 2026年3月
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日本学術振興会 科学研究費助成事業 国際共同研究加速基金(国際共同研究強化(B)) 2021年10月 - 2025年3月
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日本学術振興会 科学研究費助成事業 基盤研究(B) 2020年4月 - 2025年3月