Methyl jasmonate induces glucosinolate accumulation by transcriptional activation of biosynthetic genes in kale (Brassica oleracea var. acephala DC.) seedlings

Abstract

Methyl jasmonate (MeJA) serves as a pivotal signaling molecule orchestrating plant secondary metabolism. However, the regulatory influence of MeJA on glucosinolate (GSL) profiles, associated gene expression, and genotype-dependent responses in kale (Brassica oleracea var. acephala DC.) seedlings remains to be further investigated. Here, we investigated the responses of two kale lines ('W3′ and 'R6′) to foliar application of 100 μmol/L MeJA. Using ultra-high performance liquid chromatography quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF–MS/MS), we identified 15 GSL components distributed across the two lines. Notably, MeJA treatment preferentially promoted the accumulation of GSLs with documented or proposed health benefits, among which 1-hydroxyindol-3-ylmethyl GSL (1HGBS) exhibited the most pronounced increase, with 3.90-fold and 1.13-fold increases in 'W3′ and 'R6′, respectively, relative to the control level. Quantitative real-time PCR (qRT-PCR) analysis revealed that MeJA significantly upregulated the expression of key biosynthetic genes involved in GSL production. Specifically, BoMYB51 expression was upregulated 11.00-fold in 'W3′ and 8.48-fold in 'R6′ relative to the control. In addition, MeJA enhanced antioxidant capacity, as evidenced by increased total phenolics and flavonoid contents, as well as higher DPPH radical scavenging activity in both lines. Collectively, these findings demonstrate that exogenous MeJA induces GSL accumulation in kale seedlings through transcriptional activation of biosynthetic genes, accompanied by genotype-specific enhancement of antioxidant capacity. Our results provide insights into the genotype-dependent improvement of kale's functional quality through MeJA application.