分子進化の中立理論をドロソフィラのゲノムデータで検証する
Justin C Fay1, Gerald J Wyckoff, Chung-I Wu
1Committee on Genetics, University of Chicago, Chicago, Illinois 60637, USA. jcfay@lbl.gov
Nature
|March 5, 2002
まとめ
陽性選択は,中性的なプロセスだけでなく,タンパク質の進化を駆動する. 分析によると,適応的進化は,これまで考えられていたよりも高いペースで起こり,特定の遺伝子に影響を及ぼしています.
科学分野:
- 進化生物学の進化生物学について
- 分子進化は分子進化である.
- 集団遺伝学 人口遺伝学
背景:
- 陽性選択がタンパク質の進化に与える貢献は,まだ議論されている.
- 中性理論は,ポリモルフィズムと分岐の相等なアミノ酸 (A) と同義語 (S) の比率を予測する.
- 観察されたより高いA/S分散比は,しばしばポジティブな選択に起因するが,選択的制約の増加は,別の説明である.
研究 の 目的:
- タンパク質の進化におけるポジティブ・セレクションの役割を調査する.
- A/S比率の差異の説明として,ポジティブな選択と選択的制約の増大を区別する.
- 遺伝子と種間のポジティブ・セレクションの流行と影響を評価する.
主な方法:
- アミノ酸 (A) と同義語 (S) のポリモルフィズムと分岐比の比較分析.
- ドロソフィラ・メラノガスターとドロソフィラ・シミュランスの遺伝子特有の進化パターンの検討.
- 進化速度を評価するためのA/S比の種間比較.
主要な成果:
- 偏差のA/S比は,多形性のDrosophila.の2倍でした.
- この違いは,遺伝子のサブセットに限定され,それも加速進化を示した.
- 複数の種において,より高いA/S分岐比が観察され,これは適応的進化が広範囲に広がっていることを示している.
結論:
- 加速した進化の遺伝子特異的なパターンは,選択的制約の増大ではなく,ポジティブな選択をドライバーとして支持しています.
- 適応的進化は,分子進化の中立理論が予測するよりも,著しく高い速度で起こります.
- ポジティブ・セレクションは,様々な種のタンパク質の進化を形作る上で重要な役割を果たします.
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