Macrofungi promote plant phosphorus uptake by regulating soil microbial functions in temperate grasslands

Phosphorus (P) is one of the important elements limiting growth of most vegetation in grasslands. The presence of macrofungi in the grassland fairy ring alleviates the limiting effect of P on plants growth, which plays a pivotal role in the formation of lush-green vegetation band. However, the mechanism by which macrofungi promote plant P uptake remains poorly understood. Here, we elucidated the microbial processes underlying macrofungi-induced promotion of plant P uptake through metagenomic sequencing analysis. A pot experiment was also conducted to verify the direct effect of macrofungi on plant P uptake. Our results demonstrated that macrofungi intrinsically possess a significant ability to increase plant-available P concentration in soils, thereby promoting the growth of above- and under-ground of Leymus chinensis. Furthermore, our results showed that the presence of macrofungi significantly increased mycorrhizal colonization compared to the zone without macrofungi, which may promote the interaction between mycorrhizal fungi and plants. Meanwhile, macrofungi up-regulated the abundance of genes involved in inorganic P-solubilization and organic P-mineralization, especially genes encoding phytase (appA, phy), acid phosphatase (phoN, olpA), C-P lyase (phnFGHIJKLMNP), and quinoprotein glucose dehydrogenase (gcd). Notably, random forest analysis identified that the gene encoding phytase was a key driver of the elevated plant-available P concentration in fairy rings. Among the microorganisms involved in phytase, the presence of macrofungi significantly increased the relative abundance of Proteobacteria (Alphaproteobacteria and Gammaproteobacteria). In summary, macrofungi in the grassland fairy ring promote plant P uptake through a dual regulatory mechanism involving their own P-mobilizing capacity and the P-related functions of other soil microorganisms. This study clarifies the key microbial mechanisms by which macrofungi drive P cycling in grassland ecosystems to facilitate plant P acquisition, providing a scientific basis for nutrient management strategies aimed at sustainable agro-pastoral production.