Effects of Sulfur and Selenium on Glucosinolate Biosynthesis in Cabbage

The effects of S and Se treatment on cabbage, especially the interactions of S and Se metabolism with the biosynthesis of glucosinolate (GSL), including glucoraphanin, which is a major aliphatic GSL in cruciferous vegetables and the precursor of the anticancer compound sulforaphane, were examined. Cabbage plants were treated with sulfate and selenite (SeO32-), and the total S, Se, and GSL contents of cabbage head and outer foliage leaves were measured. Results showed that selenite treatment was beneficial to GSL biosynthesis and Se accumulation in cabbage head and outer foliage leaves. GSL synthesis was induced by exogenous selenite-elevated sulfate treatment at certain concentration ratios, i.e., 50-mu M selenite + 1-mM sulfate or 100-mu M selenite + 4-mM sulfate. A high exogenous sulfate concentration was more favorable to GSL accumulation than a low sulfate concentration. According to the relative expression of genes on GSL synthesis, an increase in the GSL content was attributed to the upregulation of gene expression and possible transportation from the outer foliage leaf to the head of cabbage. These results might be helpful for increasing the health benefits of cabbage by supplying exogenous S and Se. Further research should explore the effects of sulfate and selenite on GSL precursor substances to reveal the reason why total GSL contents increased.