Microbial Phosphate Solubilization Promotes Rare Earth Element Accumulation in the Hyperaccumulator Dicranopteris linearis from China

Plant and rhizosphere soil samples of the rare earth element (REE) hyperaccumulator plant Dicranopteris linearis were collected across tropical and subtropical China to elucidate how rhizosphere microbiota drive soil REE solubilization and accumulation in this species. The results show that this facultative REE hyperaccumulator species grows under severe phosphorus deficiency conditions, with soil available phosphorus concentrations ∼2 mg kg-1 and a leaf nitrogen-to-phosphorus ratio >20. The core rhizosphere microbiota comprise 111 OTUs (occupancy >95%, relative abundance >0.1%), with community structure primarily correlated with soil phosphorus availability, rather than with geographical location or climatic variables. Foliar phosphorus and REE concentrations are positively associated with soil total phosphorus concentrations and glucose dehydrogenase (GCD) gene abundance─a key biomarker of microbial phosphate solubilization activity─but exhibit no significant association with soil available phosphorus or soil extractable REE concentrations. Combined 16S rRNA sequencing and metagenomic analyses further reveal abundant phosphate-solubilizing microbes within the core microbiome. These results show that REE mineral weathering in the rhizosphere soil and subsequent accumulation in D. linearis are side effects of phosphate solubilization promoted by the rhizosphere microbiome under phosphorus deficiency conditions.