Effects of P. spegazzinii on JA, JA-Ile, and SA in M. micrantha. A) Levels of JA-Ile, JA, and SA in leaves of M. micrantha at CK, EL, and TI stages. CK indicates the uninfected plants by rust; PS indicates rust-infected leaves; EL and TI stages indicate the early stage of infection and TIs (see legend of Fig. 1). Values represent the mean ± Sd derived from 5 biological replicates. B) Relative mRNA levels of key genes involved in JA-Ile, JA, and SA biosynthesis and JA-ILE degradation in all stages of rust infection. Values represent the mean ± Sd derived from 3 biological replicates. JA-Ile synthesis gene included JAR1; JA-Ile degradation genes included IAR3.1, ILL6, and CYP94C1; JA synthesis genes included LOX2, AOS, OPR3, and MFP2; SA synthesis genes included ICS1, PAL1, and EPS1. C) Inhibitory effect of exogenous Me-JA and SA on the development of P. spegazzinii. The infected leaves were sprayed with exogenous Me-JA and SA with a concentration of 1 mol L⁻¹ once a day, respectively. After 10 d of treatment, the leaf was collected to observe the infection status of P. spegazzinii. D) Effect of exogenous Me-JA on mRNA level of SA biosynthesis genes in M. micrantha leaves. Values represent the mean ± Sd derived from 3 biological replicates. E) Expression pattern of key genes in JA, JA-Ile, and SA biosynthesis and JA-Ile degradation pathways, and content variation of JA, JA-Ile, and JA during all stages of rust infection. The key genes of JA-Ile degradation included IAR3.1, ILL6, and CYP94C1; the key genes of JA biosynthesis included LOX2, AOS, OPR3, and MFP2; the key gene of JA-Ile biosynthesis was JAR1; the key genes of SA biosynthesis included ICS1, PAL1, and EPS1. The bars and arrow lines indicate the fold-change of metabolites content (JA, JA-Ile, and SA) and genes expression, respectively. In (A), (B), and (D), statistical significance is determined by Student's t-test: *P < 0.05.