Selenium (Se) has been widely reported to affect plant growth, nutrient cycling, and the rhizobiome. However, how Se shapes the rhizobiome and interacts with plants remains largely elusive. Pot and hydroponic experiments were employed to elucidate the regulatory mechanism of Se in the citrus rhizobiome. Compared to the control, soil Se application significantly increased the root biomass (34.7%) and markedly reduced rhizosphere HCl-P, H₂O-P, NaHCO₃-IP, and residual-P of citrus, which were related to the variation of citrus rhizobiome. Se primarily enriched Proteobacteria and Actinobacteria as well as the phosphorus (P) functional genes phod and pqqc. Further study revealed that Se altered the metabolite profile of root exudate, particularly enhancing the abundance of l-cyclopentylglycine, cycloleucine, l-proline, l-pipecolic acid, and inositol, which played a key role in reshaping the citrus rhizobiome. These metabolites could serve as both nutrient sources and signaling molecules, thus supporting the growth or chemotaxis of the functional microbes. These bacterial taxa have the potential to solubilize P or stimulate plant growth. These findings provide a novel mechanistic understanding of the intriguing interactions between Se, root exudate, and rhizosphere microbiomes, and demonstrate the potential for utilizing Se to regulate rhizobiome function and enhance soil P utilization in citrus cultivation.

中文翻译：

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硒介导的柑橘根瘤菌塑造促进根系生长和土壤磷活化


据广泛报道，硒 (Se) 会影响植物生长、养分循环和根瘤菌。然而，硒如何塑造根瘤菌并与植物相互作用仍然很大程度上难以捉摸。采用盆栽和水培实验来阐明柑橘根瘤菌中硒的调节机制。与对照相比，土壤施硒显着增加了根系生物量（34.7%），显着降低了根际HCl-P、H ₂ O-P、NaHCO ₃ -IP和残留-P柑橘的变化，与柑橘根瘤菌的变异有关。 Se 主要富集变形菌门和放线菌门以及磷 (P) 功能基因 phod 和 pqqc。进一步的研究表明，硒改变了根系分泌物的代谢特征，特别是提高了L-环戊基甘氨酸、环亮氨酸、L-脯氨酸、L-哌啶酸和肌醇的丰度，这在重塑柑橘根瘤菌中发挥了关键作用。这些代谢物可以充当营养源和信号分子，从而支持功能微生物的生长或趋化性。这些细菌类群具有溶解磷或刺激植物生长的潜力。这些发现为硒、根系分泌物和根际微生物群之间有趣的相互作用提供了新的机制理解，并证明了利用硒调节根际生物群功能和增强柑橘栽培中土壤磷利用率的潜力。