Combined transcriptome and metabolome analyses reveal the effects of selenium on the growth and quality of .

Thunb () is an important medicinal and edible plant with outstanding functionality for selenium (Se) biofortification. However, the molecular response of to exogenous Se has not been fully elucidated. In this study, the effects of different levels of Se on growth and quality were explored by transcriptome, metabolome and biochemical analyses. The results showed that the total Se and organic Se content in bulbs increased with increasing Se dosage (0-8.0 mmol/L). Moreover, Se stimulated the growth of at low level (2.0 mmol/L) but showed an inhibitory effect at high levels (≥4.0 mmol/L). Metabolomic and biochemical analyses revealed that the bulb weight and the content of amino acid, soluble sugar, and soluble protein were significantly increased in the 2.0 mmol/L Se treatment compared with those in the control (0 mmol/L Se). Transcriptome and metabolome analyses revealed that the significant upregulation of the , and genes promoted glycerophospholipid accumulation. Additionally, the significantly upregulated and downregulated , , and genes coordinate to the regulation of amino acid biosynthesis. The significantly upregulated , and genes were involved in soluble sugar accumulation under Se treatment. In summary, this study identified the optimal Se concentration (2.0 mmol/L), which significantly improved the growth and nutritional quality of and contributed to understanding the combined effects of Se treatment on the expression of genes and the accumulation of metabolites in bulbs.