host mechanism for preventing partner's cheating in legume-rhizobia symbiosis

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K06282
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 44030:Plant molecular biology and physiology-related
• Research Institution: National Institute for Basic Biology
• Principal Investigator: Nakagawa Tomomi 基礎生物学研究所, 共生システム研究部門, 特別協力研究員 (90396812)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 根粒菌 / マメ科植物 / cheating

Outline of Final Research Achievements

Maintenance of good relationship is a key issue for our lives although the difficulty is always bothering us. On the other hand, legumes keep mutualistic relationships with soil bacteria, called rhizobia, more than 70 million years and provide carbon nutrients to rhizobia in exchange for the supply of nitrogen nutrient from rhizobia. In this relationships, rhizobial cheatings such as receiving carbon nutrients without nitrogen nutrients supply are rarely known in natural environment. We are focusing on this and studying the host mechanism for preventing partner's cheating in legume-rhizobia symbiosis.
We artificially create cheating rhizobia by disrupting genes for nitrogen fixation. The cheating rhizobia can infect and induce small nodules on host roots. Inside these nodules, cheating rhizobia are eliminated by host digestion. In contrast, honest rhizobia are markedly increased and released to surrounding soil. As a result, "honest rhizobia" are dominant around leguminous plants.

Free Research Field

植物微生物相互作用

Academic Significance and Societal Importance of the Research Achievements

「異なる生物同士がどのように協調しあえるのか？」という問題は、自然界だけではなく我々人間社会においても常に重要な問題である。数理学的には少数で協調-非協調の二択などの限られた状況における解析などが行われているが、自然界や実社会のように無数の参加者があらゆる選択肢を持つ条件で理想的な答えを見つけるのは不可能である。マメ科植物は7千万年以上も根粒菌と相利共生を行っており、共生パートナーによる裏切り・不正などがほとんど問題にならない。我々が発見した「信賞必罰」を明確にして誠実なパートナーを維持する仕組みは、協調関係を築いて維持するための究極の答えであると期待される。