Methyl Jasmonate Enhances HXK2-Mediated Indolic Glucosinolate Biosynthesis in Broccoli

Epidemiological studies show that consuming cruciferous vegetables, such as broccoli, lowers the risk of malignant tumors, an effect largely attributed to glucosinolates and their hydrolysis products. In plants, glucosinolates also act as a "sulfur-bomb" defense against biotic and abiotic stresses, underscoring their dual importance for human health and crop resilience. While the biosynthetic framework of glucosinolates has been well resolved in Arabidopsis thaliana, its regulation in economically relevant Brassica crops remains less understood. Here, we investigated the effect of exogenous methyl jasmonate (MeJA) on the glucosinolate accumulation in broccoli sprouts. MeJA treatment enhanced the antioxidant capacity and triggered a significant increase in the glucosinolate content. Transcriptomic analysis revealed MeJA-dependent reprogramming of genes involved in glucosinolate biosynthesis and degradation alongside modules regulating redox balance, carbohydrate and sulfur metabolism, and flavonoid production. Notably, the carbohydrate-related genes, especially hexokinase gene BoHXK2^LF, were significantly upregulated. Functional validation via hairy-root overexpression of BoHXK2^LF demonstrated a marked increase in neoglucobrassicin, indolic glucosinolates, and total glucosinolates, an effect that was further amplified by coapplication of MeJA. Collectively, these results highlight the potential of MeJA and BoHXK2^LF to enhance broccoli's nutritional value and stress resilience of broccoli.