Root Biology Center, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
Curr Biol. 2022 Oct 24;32(20):4337-4349.e5. doi: 10.1016/j.cub.2022.08.019. Epub 2022 Sep 1.
Symbiotic nitrogen fixation provides large amounts of nitrogen for global agricultural systems with little environmental or economic costs. The basis of symbiosis is the nutrient exchange occurring between legumes and rhizobia, but key regulators controlling nutrient exchange are largely unknown. Here, we reveal that magnesium (Mg), an important nutrient factor that preferentially accumulates in inner cortical cells of soybean nodules, shows the most positive correlation with nodule carbon (C) import and nitrogen (N) export. We further identified a pair of Mg transporter genes, GmMGT4 and GmMGT5, that are specifically expressed in the nodule cortex, modulating both nodule Mg import and C-N transport processes. The GmMGT4&5-dependent Mg import activates the activity of a plasmodesmata-located β-1,3-glucanase GmBG2 and consequently keeps plasmodesmata permeable for C-N transport in nodule inner cortical cells. Our studies discovered an important regulating pathway for host plants fine-tuning nodule C-N trading to achieve optimal growth, which may be helpful for optimizing nutrient management for soybean production.
共生固氮为全球农业系统提供大量的氮，几乎没有环境或经济成本。共生的基础是豆科植物和根瘤菌之间发生的养分交换，但控制养分交换的关键调节剂在很大程度上尚不清楚。在这里，我们揭示了镁（Mg），一种优先在大豆根瘤内皮层细胞中积累的重要营养因子，与根瘤碳（C）输入和氮（N）输出呈最正相关。我们进一步鉴定了一对镁转运体基因 GmMGT4 和 GmMGT5，它们在皮层中特异性表达，调节根瘤镁的输入和 C-N 转运过程。GmMGT4&5 依赖的镁输入激活质膜定位的β-1,3-葡聚糖酶 GmBG2 的活性，从而保持质膜在根瘤内皮层细胞中的通透性，以进行 C-N 转运。我们的研究发现了一个宿主植物微调根瘤 C-N 交换以实现最佳生长的重要调节途径，这可能有助于优化大豆生产中的养分管理。
