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

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 mu M significantly reduced disease occurrence and lesion diameter after R. stolonifer infection during 60 h of storage at 20 degrees 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.

Automated summary

MeJA treatment significantly reduces disease occurrence and lesion diameter caused by R. stolonifer in peaches during postharvest storage. It promotes the activity of CHI and GLU, elevates the expression levels of PpLOX, PpAOS, and PpOPR3, and stimulates a specific priming defense against Rhizopus rot in peaches. The transcription factor PpWRKY45 plays a role in MeJA-primed defense against R. stolonifer by activating JA biosynthetic and PR genes in peach fruit.