Fig. 6: Move-up CmoKARI1 improves cucumber chilling tolerance by specifically inducing the JA-Ile signaling pathway.

a Phenotypes, b Relative electrolyte permeability (REP), and c MDA content in two-leaf-old Super::CmoKARI1-GFP transgenic (TG) and wild-type cucumber seedlings treated with H₂O control, 300 μM Ile, 100 μM JA, 200 μM MeJA, 100 μM JA-Ile, and 200 μM Jarin-1 before and after 12 h of chilling conditions. H₂O was used as the control. n = 4 replicate pools were included, with each pool containing 12 plants, for each treatment (mean ± s.d., one-way ANOVA followed by Duncan’s multiple comparisons test within each genotype, p < 0.05; p-values at the top indicating the statistical difference between genotypes within each treatment group determined by one-way ANOVA). d Relative gene expression levels of CsaCBF1 and CsaJAR1 in the first true leaf under different growth conditions. Each treatment includes n = 3 biological replicates, with 12 individual plants per replicate (mean ± s.d., one-way ANOVA followed by Duncan’s multiple comparisons test within each genotype, p < 0.05; p-values at the top indicating the statistical difference between WT and TG within each treatment group determined by Student t-test). Cucumber ACTIN7 was used as an internal reference. e Content of JA, MeJA, JA-Ile, and OPDA was determined in wild-type (WT) and Super::CmoKARI1-GFP transgenic (TG#4) under 28 °C and 4 °C conditions. Each treatment includes n = 3 biological replicates, with 4 individual plants per replicate (mean ± s.d., one-way ANOVA followed by Duncan’s test, p < 0.05). f Schematic model depicting the improvement of cold tolerance in cucumber scion under cold stress through the pumpkin rootstock-derived mobile CmoKARI1. The long-distance movement of CmoKARI1 accelerates isoleucine biosynthesis, providing substrates for JA-Ile biosynthesis controlled by CsaJAR1. The accumulation of JA-Ile activates the CBF-COR pathway, thereby enhancing chilling tolerance in cucumber. Source data are provided as a Source Data file.