Legume-specific recruitment of rhizobia by hyphae of arbuscular mycorrhizal fungi

作者：Jiadong He, Judith Van Dingenen, Sofie Goormachtig, Maryline Calonne, Stéphane Declerck · 发表于：The ISME Journal · 年份：2025 · DOI：10.1093/ismejo/wraf100 · 被引用次数：7 · 研究领域：Mycorrhizal Fungi and Plant Interactions、Legume Nitrogen Fixing Symbiosis、Plant-Microbe Interactions and Immunity

The legume-rhizobia symbiosis possesses great potential for sustainable agriculture because of its ability to fix atmospheric nitrogen, reducing crop dependence on nitrogen fertilizers. Rhizobia recognize the host legume through flavonoids released by the roots. These signals are detected by bacteria typically over a few millimeters. Recent research has shown that arbuscular mycorrhizal fungi extend this recognition beyond 15 cm by transporting flavonoids along their hyphae. In soil, common mycorrhizal networks (CMNs) linking plants are formed by arbuscular mycorrhizal fungi. We hypothesized that such networks linking different legumes can transmit host-specific signals, guiding rhizobia to their appropriate hosts. Using in vitro and greenhouse microcosms, we linked Medicago truncatula and Glycine max via a CMN of Rhizophagus irregularis and inoculated GFP-labeled Sinorhizobium meliloti and mCherry-labeled Bradyrhizobium diazoefficiens on the hyphae. S. meliloti preferentially migrated towards M. truncatula, whereas B. diazoefficiens preferentially migrated towards G. max (155 ± 8 and 13 ± 3 nodules, respectively). This was confirmed in the greenhouse with a higher concentration of S. meliloti (2.1-2.5 × 105 CFU·g-1) near M. truncatula and a higher concentration of B. diazoefficiens (1.5-1.6 × 105 CFU·g-1) near G. max (71-82 and 15-18 nodules, respectively). Metabolomics revealed host-specific flavonoids in hyphal exudates: M. truncatula-connected hyphae released DL-liquiriti...