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 BoHXK2LF, were significantly upregulated. Functional validation via hairy-root
overexpression of BoHXK2LF 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 BoHXK2LF to
enhance broccoli’s nutritional value and stress resilience
of broccoli.