PpWRKY45 is involved in methyl jasmonate primed disease resistance by enhancing the expression of jasmonate acid biosynthetic and pathogenesis-related genes of peach fruit

Abstract

• 10 μM of MeJA effectively inhibited soft rot caused by R. stolonifer. • MeJA elevated the expression of JA biosynthetic and PR genes. • MeJA induced disease resistance against R. stolonifer by priming of defense responses. • PpWRKY45 activated defense-related gene expression by bind to their promoters. • PpWRKY45 is involved in MeJA-primed defense by enhancing defense-related gene expression. Methyl jasmonate (MeJA) and WRKY transcription factors (TFs) are documented to exert vital defensive functions. Research concerning WRKY TFs together with MeJA-primed defense against Rhizopus stolonifer in peach fruit is still in its infancy. In the present study, the mode of MeJA on inducing resistance against soft rot caused by Rhizopus stolonifer in peaches during the postharvest storage and the involvement of WRKY TFs were investigated, and the results manifested that MeJA at 10 μM significantly reduced disease occurrence and lesion diameter after R. stolonifer infection during 60 h of storage at 20 °C. Moreover, the MeJA treatment promoted the activity of CHI and GLU and elevated the expression levels of PpLOX , PpAOS and PpOPR3 . More importantly, the expression of PpCHI , PpGLU , PpPR-like , PpLOX , PpAOS and PpOPR3 were substantially and rapidly elevated in the peach fruit that pretreated with MeJA and inoculated with R.stolonifer , indicating that MeJA stimulated a specific priming defense against Rhizopus rot in peaches. Furthermore, a MeJA-related transcription factor PpWRKY45 was identified and characterized as a nucleus-localized protein that could activate the expression of PpCHI, PpGLU, PpPR-like, PpLOX, PpAOS and PpOPR3 by binding to W-box elements in their promoters. These results indicate that PpWRKY45 is involved in MeJA-primed defense against R . stolonifer by activating JA biosynthetic and PR genes of peach fruit.