State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, South China Agricultural University, Guangzhou, 510642, China.
Root Biology Center, South China Agricultural University, Guangzhou, 510642, China.
Mycorrhiza. 2020 May;30(2-3):285-298. doi: 10.1007/s00572-020-00955-x. Epub 2020 Apr 15.
Arbuscular mycorrhizal (AM) symbiosis plays crucial roles in plant nutrient uptake. However, little is known about the combined effects of phosphorus (P) and magnesium (Mg) on mycorrhizal symbiosis. In the present study, a pot experiment was carried out using two soybean genotypes in the presence or absence of Rhizophagus irregularis inoculation under different P and Mg conditions. The results showed that plant growth promotion by mycorrhizal symbiosis was associated with P-starved nutrition status, high Mg supply augmented the efficiency of AM symbiosis in low P, and high Mg relieved the inhibitory effect of high P availability on AM symbiosis. The P-efficient genotype HN89 was more responsive to Mg application than the P-inefficient genotype HN112 when inoculated with Rhizophagus irregularis. The results from a comparative RNA sequencing analysis of the root transcriptomes showed that several carbon metabolism pathways were enriched in mycorrhizal roots in low P plus high Mg. Accordingly, the expression levels of the key genes related to carbon metabolism and transport were also upregulated in mycorrhizal roots. Conversely, the Mg-deficient mycorrhizal plants showed increased sucrose, glucose, and fructose accumulations in shoots. Overall, the results herein demonstrate that P and Mg interactively affect mycorrhizal responses in plants, and high Mg supply has a profound effect on P-starved mycorrhizal plant growth through promotion of photosynthate metabolism and transport in soybean.
丛枝菌根（AM）共生在植物养分吸收中起着至关重要的作用。然而，人们对磷（P）和镁（Mg）对菌根共生的综合影响知之甚少。本研究采用盆栽试验，在不同 P 和 Mg 条件下，利用两种大豆基因型，在存在或不存在 Rhizophagus irregularis 接种的情况下，研究了 AM 共生的相互作用。结果表明，菌根共生对植物生长的促进作用与 P 饥饿的营养状态有关，高 Mg 供应增强了低 P 下 AM 共生的效率，高 Mg 缓解了高 P 可用性对 AM 共生的抑制作用。与 P 低效基因型 HN112 相比，接种 Rhizophagus irregularis 的 P 高效基因型 HN89 对 Mg 应用更为敏感。对根转录组进行比较 RNA 测序分析的结果表明，在低 P 加高 Mg 条件下，几个碳代谢途径在菌根根中富集。因此，与碳代谢和运输相关的关键基因在菌根根中的表达水平也上调。相反，缺 Mg 的菌根植物在地上部分积累了更多的蔗糖、葡萄糖和果糖。总的来说，这些结果表明 P 和 Mg 相互作用影响植物的菌根反应，高 Mg 供应通过促进大豆菌根植物光合作用产物的代谢和运输，对 P 饥饿的菌根植物生长有深远影响。
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