Institute of Ecology and Evolutionary Biology, National Taiwan University, Taipei, Taiwan.
Institute of Plant Biology, National Taiwan University, Taipei, Taiwan.
BMC Plant Biol. 2024 Aug 15;24(1):780. doi: 10.1186/s12870-024-05488-5.
The symbiosis among plants, rhizobia, and arbuscular mycorrhizal fungi (AMF) is one of the most well-known symbiotic relationships in nature. However, it is still unclear how bilateral/tripartite symbiosis works under resource-limited conditions and the diverse genetic backgrounds of the host.
Using a full factorial design, we manipulated mungbean accessions/subspecies, rhizobia, and AMF to test their effects on each other. Rhizobia functions as a typical facilitator by increasing plant nitrogen content, plant weight, chlorophyll content, and AMF colonization. In contrast, AMF resulted in a tradeoff in plants (reducing biomass for phosphorus acquisition) and behaved as a competitor in reducing rhizobia fitness (nodule weight). Plant genotype did not have a significant effect on AMF fitness, but different mungbean accessions had distinct rhizobia affinities. In contrast to previous studies, the positive relationship between plant and rhizobia fitness was attenuated in the presence of AMF, with wild mungbean being more responsive to the beneficial effect of rhizobia and attenuation by AMF.
We showed that this complex tripartite relationship does not unconditionally benefit all parties. Moreover, rhizobia species and host genetic background affect the symbiotic relationship significantly. This study provides a new opportunity to re-evaluate the relationships between legume plants and their symbiotic partners.
植物、根瘤菌和丛枝菌根真菌（AMF）之间的共生关系是自然界中最著名的共生关系之一。然而，在资源有限的条件下以及宿主多样化的遗传背景下，双边/三方共生如何发挥作用仍不清楚。
我们采用完全析因设计，操纵绿豆品种/亚种、根瘤菌和 AMF，以测试它们之间的相互作用。根瘤菌作为一种典型的促进剂，增加了植物的氮含量、植物重量、叶绿素含量和 AMF 定殖。相比之下，AMF 导致植物的权衡（为获取磷而减少生物量），并作为竞争菌减少根瘤菌的适应性（根瘤重量）。植物基因型对 AMF 适应性没有显著影响，但不同的绿豆品种有不同的根瘤菌亲和力。与以往的研究不同，在存在 AMF 的情况下，植物和根瘤菌适应性之间的正相关关系减弱，野生绿豆对根瘤菌的有益作用和 AMF 的衰减更为敏感。
我们表明，这种复杂的三方关系并不无条件地使所有各方受益。此外，根瘤菌物种和宿主遗传背景对共生关系有显著影响。本研究为重新评估豆科植物与其共生伙伴之间的关系提供了新的机会。
