Bacteria from the rhizosphere of a selenium hyperaccumulator plant can improve the selenium uptake of a non-hyperaccumulator plant

It is unknown whether soil microbiota and soil bacteria isolated from the rhizosphere of selenium hyperaccumulator plants can affect selenium absorption by selenium non-hyperaccumulator plants. Here, we used pot experiments and split root experiments to investigate the role of soil microbiota and isolated rhizosphere bacteria from a selenium hyperaccumulator plant (Cardamine violifolia) in affecting selenium absorption by a selenium non-hyperaccumulator plant (Brassica napus), combining root metabolism analysis, microbiome profiling, strain isolation and its selenium absorption functional validation. We found that soil microbiota of Cardamine violifolia significantly increased the root selenium content by 31.8% and regulated root exudation by Brassica napus. Additionally, the application of upregulated long-chain organic acids + amino acids, long-chain organic acids + short-chain organic acids, ethanolamine, and 2-ketobutyric acid increased the selenium contents in the roots of Brassica napus by 69.6%, 38.4%, 81.2%, and 48.8%, respectively. Further investigation revealed that dominant bacteria were significantly enriched in the rhizosphere of C. violifolia compared to B. napus. After that, we isolated the rhizosphere bacteria of Cardamine violifolia and observed that Bacillus sp.-2, Chryseobacterium sp., and Pseudomonas sp., as well as their combined communities, significantly improved selenium absorption in Brassica napus. Moreover, the combined bacterial communities significantly regulated specific-root metabolism, enhanced rhizosphere soil available selenium content, promoted root development, increased expression levels of genes encoding selenium transporter in root. These findings provide insights into utilizing rhizosphere bacteria of selenium hyperaccumulator plants to increase selenium absorption by non-hyperaccumulator plants.

Graphical Abstract