Rhizosphere phosphatase hotspots: microbial-mediated P transformation mechanisms influenced by maize varieties and phosphorus addition

Rhizosphere serves as a hotspot for phosphatase exudation, which is instrumental in organic P mineralization and thereby facilitates enhanced P uptake by plants. However, further exploration is required to elucidate mechanisms of P transformation regulated by microorganisms in rhizosphere hotspots.

Soil zymography was used to visualize rhizosphere hotspots associated with acid and alkaline phosphatase activities following P addition in two maize genotypes, Zhengdan958 (ZD958) and Xianyu335 (XY335). Metagenomic sequencing was used to investigate shifts in abundance and composition of P cycle genes and microbial communities within phosphatase hotspots.

ZD958 exhibited higher shoot biomass than XY335 under same P conditions. Hotspots of phosphatase activity were predominantly located in the maize rhizosphere and decreased following P addition. Specifically, P addition resulted in an increase in the abundance of P-uptake and transport genes pstSCAB and a decrease in the abundance of P-starvation regulation gene phoB and inorganic P solubilization gene gcd in ZD958. The relative abundance of phytase-encoding gene (phy) significantly increased with P addition and correlated with soil available P (AP) in XY335. Among the microbial taxa containing hub genes, Streptomyces emerged as the most crucial predictor of soil AP and exhibited a significantly positive relationship with AP for both maize genotypes.

Our results visualized the rhizosphere phosphatase hotspots, revealing that the genes regulating P cycling differed while Streptomyces harboring P cycling hub genes improve P availability in both maize genotypes. These findings provide a scientific basis for increasing the P efficiency employing microbiology.