Figure 6

Involvement of JA signaling in B. rapa response to thrips feeding. (A-D) Expression of marker genes for JA response in B. rapa was induced by thrips feeding. BrVSP2 (A), BrLOX2 (B), BrAOS (C), and BrAOC2 (D) are brassica counterparts of Arabidopsis marker genes of the JA pathway and JA biosynthesis. Twenty-five adult females fed on five 2-week-old plants per pot. After 0, 1, 2, and 5 days, total RNA was prepared from the plants with (+Feeding) or without (-Feeding) thrips, and first-strand cDNA was synthesized for PCR analysis. The expression level of each gene was normalized to the expression of BrACT2 (control). Mean ± SD based on three replications. (E) Proposed model of the biosynthesis of JA in Arabidopsis. (F) Effect of thrips feeding on the biosynthesis of JA in B. rapa. Ten adult females fed on a 2-week-old plant (+Feeding). A control plant was kept without thrips (-Feeding). At the beginning of the experiment (0 h) and after 1 day from the start of feeding, 1 g of plant tissue was sampled for measurement of endogenous JA (JA + methyl JA). Means ± SD of three independent measurements. Different letters indicate statistically significant differences between treatments (Tukey-Kramer HSD test; p < 0.05).