Mechanism of lactic acid bacterial fertiliser on enhancing growth and selenium absorption of rapeseed revealed by transcriptome analysis and rhizosphere bacterial diversity.

There is a widespread phenomenon of insufficient selenium (Se) intake globally. While Se-enriched bacterial fertilisers have shown potential for biofortification, their integrated effects on plant physiological responses, antioxidant defense, rhizosphere bacterial community assembly, and leaf transcriptomic regulation remain poorly understood. A pot experiment was conducted with three treatments: control (CK), Se fertiliser without bacterial inoculation (S), and Se-enriched bacterial LB-2 fertiliser (L). Plant growth parameters, antioxidant enzyme activities (SOD, CAT, POD), organic Se conversion rate, rhizosphere soil bacterial community (16S rRNA gene sequencing), and leaf transcriptome were analyzed. Compared with the S treatment, the L treatment significantly increased plant height, fresh weight, soluble sugar content, and achieved a higher organic Se conversion rate (79.26%). Antioxidant enzyme activities in rapeseed leaves under the L treatment were more effective in reducing oxidative stress induced by exogenous Na2SeO3 than those in the S treatment. Rhizosphere soil bacterial diversity analysis revealed that the L treatment significantly enriched beneficial rhizosphere taxa, including Sphingomonas, Paraflavitalea, and Neorhizobium, which may enhance soil fertility and plant growth. Transcriptome sequencing of rapeseed leaves showed significant alterations in the expression of key genes involved in secondary metabolic pathways, including P5CS2, NCED4, and ZEP.The Se-enriched bacterial LB-2 fertiliser developed in this study offers a potential solution to alleviate Se deficiency by enhancing organic Se conversion, improving antioxidant capacity, modulating rhizosphere bacterial communities, and regulating leaf secondary metabolism, thereby providing a viable strategy for increasing Se levels in food crops.