The endophytic fungus Serendipita indica reshapes rhizosphere soil microbiota to improve Salix suchowensis growth and phytoremediation

Abstract

Soil cadmium (Cd) contamination, a global issue threatening human health, can be mitigated through phytoremediation using plant growth-promoting microorganisms (PGPMs), which enhance heavy metal extraction. Endophyte Serendipita indica promotes plant growth and alleviates abiotic/biotic stress, but its role in reshaping rhizosphere microecology remains unclear. We combined in situ zymography, diffusive equilibration in thin films (DET), and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to explore Cd rhizosphere processes. S. indica inoculation significantly increased stems and leaves biomass by 36.52 % and 31.63 %, respectively, and Cd accumulation by 44.30 % in stems and 33.17 % in leaves. DET and zymography mapping showed that S. indica inoculation reduced pH and enhanced enzyme activity in the rhizosphere. LA-ICP-MS mappings revealed that S. indica increased Cd concentration in the root-soil interface and enhanced Cd and phosphorus (P) bioavailability, promoting root uptake and transport to shoots. S. indica inoculation recruited a more complex and stable network, supporting willow growth and Cd absorption. Key strains like Gemmatimonas, Subgroup_10, and Sandaracinus facilitated organic matter degradation, releasing bioavailable P and Cd, thus enhancing the phytoremediation efficiency. In summary, a mutualistic system between S. indica and willow was established, enhancing Cd phytoremediation efficiency by altering rhizosphere microenvironment and microbiome.