Metagenomics and metabolomics analysis revealed that Se-mediated Cd precipitation and nutrient cycling regulated soil-rice (Oryza sativa L) microenvironmental homeostasis under cadmium stress

Exogenous selenium (Se) addition can dynamically regulate the establishment of microbial communities, induce the expression of specific microbial functional genes, and affect the homeostasis of the soil-plant microenvironment. In this study, we used metagenomic and metabolomic analyses to investigate Se-mediated homeostatic changes and functional responses in the rhizosphere soil of rice seedlings. Results show that compared with the Cd set, selenium (1 mg/kg) Se content in the Soil and rice plant increased by 88.5 % and 99.1 %, respectively. Soil-fluorescein diacetate (S-FDA) hydrolyze enzymatic activity increased by 42.9 %, Rice on Cd enrichment coefficient increased by 71.1 %, but the transfer coefficient by 21.6 %, making a lot of cadmium ion stranded in the root, easing the toxicity of cadmium to plant. Metagenomic analysis revealed that Se bioaugmentation altered the structure and composition of the rhizosphere microbial community and induced remodeling of the rice rhizosphere microbiome. Increase the heavy metal resistance genes (cznA czcD, czcP, dltC, and CREM), nutrient cycling functional genes (atoB tktB, acs, sdhA, accA, ppdK, NRT, narB, nifD, napA, pstS, GlpQ, spoT, phoR, sucC) and heavy metal transport protein family (P-ATPase, CDF, ABC, and MIT) expression. It significantly improved the health of the rhizosphere microenvironment and alleviated soil hardening and nutrient deficiency caused by heavy metals. At the same time, in metabonomics analysis, The upregulated Differentially expressed metabolites (DEMs) were mainly in the Biosynthesis of siderophore group nonribosomal peptides, Sulfur metabolism, Ubiquinone and other terpenoid-quinone Biosynthesis, Cysteine, and methionine metabolism in enrichment significantly. The mediated reshaping of rhizosphere microorganism groups indicates that there is ane an advantage in the nutrient cycle. Also, the secondary metabolism and antioxidant capacity have significantly strengthened the ed, and the large strain caused by the death of heavy metals is a result of poor Soil. In addition, the Cyclic adenosine monophosphate (CAMP) signaling pathway was activated among the remodeling microbiomes, and the receptor protein inducer was upregulated, which activated the population response among the rhizosphere microbiomes and resulted in the overexpression of specific functional genes of each microbiome. By enhancing the resistance to heavy metals and nutrient cycling ability of the rhizosphere microbiome, the mobility and bioavailability of Cd ions were significantly reduced, the rhizosphere soil microenvironment health was improved, and the adaptability of rice to Cd stress was improved. This study reveals the Se of rice rhizosphere Cd-resistant bacteria mediating mechanisms; research for precise regulation of plant rhizosphere microorganism groups opens new avenues of research and offers a new way for crop production safety.