Geraniol treatment enhances sulforaphane content through modulation of the glucosinolate biosynthetic pathway in kale (Brassica oleracea)

Abstract Kale ( Brassica oleracea ) is a cruciferous vegetable known for health benefits, primarily due to sulforaphane, a compound with notable anticancer properties. Recently, we reported that the application of geraniol can significantly increase sulforaphane content in kale. However, the molecular mechanisms underlying this enhancement remain unexplored. In this study, we aimed to elucidate the metabolic pathways by which geraniol influences sulforaphane biosynthesis. Geraniol was applied as a 500-ppm solution, sprayed on the leaves of kale cultivated in an indoor aeroponic farm, once daily for two consecutive days, one week prior to harvest. As a result, we found that the sulforaphane content in the geraniol-treated group was 2.2 times higher than in the control group. Moreover, gene expression analysis demonstrated significant upregulation of CYP83, SUR1, and UGT, which are key genes involved in sulforaphane biosynthesis, with increases of 1.7, 1.3, and 1.1-fold, respectively, in the geraniol-treated group compared to the control group. These findings suggest that geraniol enhances sulforaphane content by upregulating genes critical to its biosynthesis.