Synergistic interplay of selenium (Se) and antimony (Sb)-oxidizing bacteria Bacillus sp. S3 alleviates the Sb toxicity in pak choi (Brassica chinensis L.) by limiting Sb uptake, enhancing antioxidant systems and regulating key metabolic pathways

Abstract

Antimony (Sb) contamination is a serious environmental concern. To detoxify Sb(III) toxicity in crops, two common strategies used are application of exogenous selenium (Se) and inoculation of antimony oxidizing bacteria. However, the potential synergistic effects of these strategies in alleviating Sb(III) stress in plants have not been fully explored. In this study, we proposed a new strategy of co-applying Se with an Sb(III)-oxidizing bacteria, Bacillus sp. S3 to reduce the growth inhibition in pak choi in Sb(III)-contaminated soil. Our findings demonstrated that Se and Bacillus sp. S3 co-application significantly increased plant growth, reduced oxidative and osmotic stress, and enhanced the antioxidant contents of pak choi, compared to either Se or Bacillus sp. S3 alone under Sb(III) exposure. Furthermore, this co-application effectively limited Sb uptake (up to 81.03%) in pak choi roots and enhanced the subcellular distribution of Sb (up to 79.58%) in shoot cell walls. Fourier-transform infrared spectroscopy (FTIR) spectra confirmed that synergistic interplay of Se and Bacillus sp. S3 could facilitate the fixation of more Sb on the cell wall by increasing the number of functional groups present in the cell walls. Transcriptome analysis revealed that the synergistic interplay of Se and Bacillus sp. S3 also triggered gene expression in key metabolic pathways involved in the defense and detoxification response to Sb(III), including the cytochrome P450 metabolism and phenylpropanoid biosynthesis pathways. These findings provide valuable insight for reducing the hazardous effects of Sb on crop growth and yield, ultimately improving the food safety of vegetable crops.