Journal Article

Genetic design of soybean hosts and bradyrhizobial endosymbionts reduces N 2 O emissions from soybean rhizosphere

Shirasu, Ken, Minamisawa, Kiwamu, Duc, Luong Van, Masuda, Sachiko, Imaizumi-Anraku, Haruko, Shenton, Matthew, Li, Feng, Suzuki, Atsuo, Sugawara, Masayuki, Itakura, Manabu, Ohkubo, Satoshi, Takahashi, Koji, Win, Khin Thuzar, Kakizaki, Kaori, Shimoda, Yoshikazu, Shibata, Arisa, Fujisawa, Yukiko, Nishida, Hanna, Tsubokura, Misa, Akiyama, Hiroko

2025

Overview

Soybeans fix atmospheric N through symbiosis with rhizobia. The relationship between rhizobia and soybeans, particularly those with high nitrous oxide (N O)-reducing (N OR) activities, can be leveraged to reduce N O emissions from agricultural soils. However, inoculating soybeans with these rhizobia under field conditions often fails because of the competition from indigenous rhizobia that possess low or no N OR activity. In this work, we utilize natural incompatibility systems between soybean and rhizobia to address this challenge. Specifically, Rj2 and GmNNL1 inhibit certain rhizobial infections in response to NopP, an effector protein. By combining a soybean line with a hybrid accumulation of the Rj2 and GmNNL1 genes and bradyrhizobia lacking the nopP gene, we develop a soybean-bradyrhizobial symbiosis system in which strains with high N OR activity predominantly infect. Our optimize symbiotic system substantially reduces N O emissions in field and laboratory tests, presenting a promising approach for sustainable agricultural practices.

• Subject: Bradyrhizobium / Crosses, Genetic / Genes, Plant / Glycine max - physiology / Greenhouse Gases / Nitrogen Cycle - physiology / Nitrous Oxide - metabolism / Phenotype / Rhizosphere / Soil - chemistry / Soil Microbiology / Symbiosis