Arms race between hosts and symbionts over sex ratio

2023 Fiscal Year Final Research Report

• Project/Area Number: 22K19351
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 45:Biology at organismal to population levels and anthropology, and related fields
• Research Institution: National Agriculture and Food Research Organization
• Principal Investigator: Kageyama Daisuke 国立研究開発法人農業・食品産業技術総合研究機構, 生物機能利用研究部門, 上級研究員 (60401212)
• Co-Investigator(Kenkyū-buntansha): 林 正幸 国立研究開発法人農業・食品産業技術総合研究機構, 植物防疫研究部門, 主任研究員 (80837609)
• Project Period (FY): 2022-06-30 – 2024-03-31
• Keywords: 進化的軍拡競争

Outline of Final Research Achievements

Most of the sexually reproducing organisms tend to have a 1:1 sex ratio, but in arthropods, symbiotic bacteria can sometimes skew the sex ratio toward females. In the lacewing Mallada desjardinsi, a strongly female-biased sex ratio induced by Spiroplasma was converted to a normal 1:1 sex ratio by fixation of a suppressor gene. Subsequently, a “hyper” strain of Spiroplasma was discovered that induces male killing regardless of the presence of suppressors, but whose frequency remains low in each population. In the Fukuyama population, the infection frequency of Spiroplasma decreased continuously each year. Genome analysis showed that the hyper strains are derived from the original strains of Spiroplasma. We also revealed the genetic structure of M. desjardinsi, including a selective sweep of the cytoplasm, probably due to Wolbachia-induced cytoplasmic incompatibility.

Free Research Field

進化生物学

Academic Significance and Societal Importance of the Research Achievements

今まであまり注目されてこなかったが、理論的に予測されていた核と細胞質との間の性比を巡る進化的軍拡競争をリアルタイムで観測するという取り組みは、生物の進化における普遍的ではあるはずだが今まで可視化されてこなかった具体的なモデルケースとなる。また、集団遺伝構造についても新たな発見があり、細胞内共生微生物の重要性を再認識させるものとなった。また天敵昆虫であるクサカゲロウについての新たな側面が明らかになったことから、農業上の応用利用といった文脈においても考慮すべき重要な視点を提供できた。