Effects of selenate on Se, flavonoid, and glucosinolate in broccoli florets by combined transcriptome and metabolome analyses

Broccoli is a nutritious vegetable popular all over the world. This study investigated the effects of different concentrations of selenate (0, 0.1, 0.2, 0.4, 0.8, and 1.6 mmol/L) on the selenium (Se), glucosinolate, and flavonoid contents of broccoli florets. Results showed that the total Se, selenomethionine, and methyl selenocysteine contents increased following selenate dosage. Interestingly, selenate treatment of 0.4 mmol/L decreased the flavonoid but increased the glucosinolate content. Metabolome analysis revealed changes in the individual contents of glucosinolates and flavonoids. Conjoint analysis of transcriptome and metabolome showed that the glucosinolate and flavonoid compounds were potentially regulated by two sulfate transporter genes (Sultr3;1 and Sultr4;2) and several cytochrome P450 genes (e.g., CYP71B21, CYP72C1, and CYP81F1). These new findings indicated that Se treatment may influence glucosinolate and flavonoid accumulation by regulating the expression of these genes. The results of this study provide some novel insights into the effects of Se on glucosinolates and flavonoids in broccoli florets and deepen our understanding of the regulatory network between some specific genes and these compounds.