Grant-in-Aid for Scientific Research (A)
|Research Institution||KYUSHU UNIVERSITY|
YAHARA Tetsukazu Kyushu University, Faculty of Science, Professor, 理学部, 教授 (90158048)
牧 雅之 福岡教育大学, 教育学部, 助教授 (60263985)
KOBAYASHI Ichizo University of Tokyo, Institute of Medical Science, Associate Professor, 医科学研究所, 助教授 (30126057)
SASAKI Akira Kyushu University, Faculty of Science, Associate Professor, 理学部, 助教授 (90211937)
粕谷 英一 九州大学, 理学部, 助教授 (00161050)
IWASA Yoh Kyushu University, Faculty of Science, Professor, 理学部, 教授 (70176535)
嶋田 正和 東京大学, 大学院総合文化研究科, 助教授 (40178950)
菊沢 喜八郎 京都大学, 生態学研究センター, 教授 (50271599)
ONOSATO Hiroshi Shinshu University, Faculty of Science, Professor, 理学部, 教授 (60273067)
TERACHI Toru Kyoto Sangyo University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (90202192)
|Project Fiscal Year
1996 – 1998
Completed(Fiscal Year 1998)
|Budget Amount *help
¥22,200,000 (Direct Cost : ¥22,200,000)
Fiscal Year 1998 : ¥6,600,000 (Direct Cost : ¥6,600,000)
Fiscal Year 1997 : ¥7,800,000 (Direct Cost : ¥7,800,000)
Fiscal Year 1996 : ¥7,800,000 (Direct Cost : ¥7,800,000)
|Keywords||Sexual reproduction / Selfish gene / Recombination / Parasites / Coevolution / Genome conflicts / 有性生殖 / 無性生殖 / 利己的遺伝子 / 組み換え / 耐病性 / 共進化 / ゲノムコンフリクト / 資源分野 / トレードオフ / 病原体 / ゲノミックインプリンティング / 性表現 / 資源分配モデル / ウイルス / 挿入変異 / ゲノム間コンフリクト|
Adaptive significance of sexual reproduction remains uncertain. One of the purposes of this project was to unravel this mystery. Pathogen-driven selection has been regarded as a likely factor that can provide a general advantage for sexual reproduction (Red Queen hypothesis). T.Yahara tested this hypothesis using Eupatorium-geminivirus system by comparingsequence divergence of ORF 04, a host-range determinant of geminivirus between viruses infecting sexual and asexual host populations. Frequency of amino acid replacements was significantly higher in sexual host populations, supporting the hypothesis.
A.Sasaki also developed a new model for gene-for-gene interactions between hosts and parasites and showed that antagonistic coevolution between hosts and parasites conserve fitness variation and make sexual reproduction advantageous.
I.Kobayashi demonstrated that restriction-modification systems are parasites of bacterial genome and developed a new hypothesis that homologous recombination ev
olved as an counter-adaptation against gemomic parasites.
Another target of this project was to describe some genetic systems under genetic conflicts and elucidate dynamics and outcomes of genetic interactions between genetic elements with conflicting interests in their transmission. Under suxual reproduction, Mendelian inheritance is a rule, but this rule is often violated by selfish behaviours of cytoplasmic genetic elements. In Raphanus, for example, male sterility is induced by a mitocondrial gene, but is restored by a nuclear gene. Outcomes of this interaction was examined in the field. Sex ratio distortion system in azuki-bean beetles, that is caused by Infection of microorganisms, was examined and complete nuclear control of sex ratio was confirmed in spite that infection of microorganism was very high.
We also studied various phenomena of genomic imprinting. Y.Iwasa developed several models which can explain some unique properties of genomic inprinting.