| Project/Area Number |
15370097
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Developmental biology
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| Research Institution | Keio University |
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Principal Investigator |
HOSHI Motonori Keio University, Faculty of Science and Technology, Professor, 理工学部, 教授 (20012411)
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| Co-Investigator(Kenkyū-buntansha) |
MATSUMOTO Midori Keio University, Faculty of Science and Technology, Associate Professor, 理工学部, 助教授 (00211574)
KOBAYASHI Kazuya Keio University, Faculty of Science and Technology, Assistant Professor, 理工学部, 助手 (50360110)
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| Project Period (FY) |
2003 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥9,900,000 (Direct Cost: ¥9,900,000)
Fiscal Year 2005: ¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 2004: ¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 2003: ¥3,500,000 (Direct Cost: ¥3,500,000)
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| Keywords | reproductive strategy / sexualizing substance / planarian / germ cell / 生殖様式転換 / 有性生殖 / 無性生殖 / ネオブラスト / テロメア / 生殖様式の転換 / 有性化物質 / 分裂誘導物質の単離・同定 / 関連遺伝子群 / 新生細胞の単離・培養・移植 / 核学的解析 |
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| Research Abstract |
Various metazoans can reproduce in multiple ways and select an alternative reproductive strategy such as asexual or sexual, and biparental or uniparental depending upon the environmental conditions and/or the phase of life cycle. However, the mechanism underlying the selection and switch of reproductive modes remains to be explored. Many freshwater planarians reproduce asexually by transverse fission as well as sexually by copulation. Asexual worms do not form any sexual organs, while sexual ones have hermaphroditic sexual organs and do not undergo fission. Some populations within the same species switch these reproductive modes seasonally.
We have established an experimental system to analyze the mechanism underlying the switch from asexual to sexual reproduction in the planarian, Dugesia ryukyuensis. If the worms of an exclusively asexual clone (OH strain) of the species are fed with sexually mature worms of Bdellocephala brunnea, an exclusively sexual species, all of them gradually develop ovaries, testes and other sexual organs within a few weeks, and then copulate, and eventually lay cocoons filled with fertilized eggs. This suggests that sexually mature worms contain a putative sexualizing substance(s) that is not very genus-specific. The fully sexualized OH worms (acquired sexuals) produce their own sexualizing substance. The head fragments lacking the sexualizing substance regenerated into asexuals, though the other portions containing the sexualizing substance regenerated into sexuals. Thus, it is most likely that they keep the sexuality by producing enough an amount of the sexualizing substance. We are trying to identify the sexualizing substance in the acquired sexuals, and have so far clarified that it is acidic, heat-stable, smaller than 0.5 kDa and pronase-resistant. NMR analysis showed that L-trp is one of candidate for sexualizing substances
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