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.

中文翻译：

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磷和镁通过改变大豆光合产物的代谢和运输对菌根共生的联合影响。


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。在本研究中，在不同的磷和镁条件下，在有或没有接种不规则根霉的情况下，使用两种大豆基因型进行了盆栽实验。结果表明，菌根共生促进植物生长与缺磷营养状态有关，高镁供应增强了低磷条件下AM共生的效率，高镁缓解了高磷有效性对AM共生的抑制作用。当接种不规则根霉时，P高效基因型HN89比P低效基因型HN112对镁施用更敏感。根转录组的比较RNA测序分析结果表明，低磷+高镁的菌根根中多种碳代谢途径富集。因此，菌根根中与碳代谢和运输相关的关键基因的表达水平也上调。相反，缺镁菌根植物的芽中蔗糖、葡萄糖和果糖积累增加。总体而言，本文的结果表明，P 和 Mg 交互影响植物中的菌根反应，并且高镁供应通过促进大豆中的光合产物代谢和运输，对缺磷的菌根植物生长产生深远影响。