A Genome-Wide DNA Methylation Survey Reveals Salicylic Acid-Induced Distinct Hypomethylation Linked to Defense Responses Against Biotrophic Pathogens

DNA methylation is a conserved regulatory mechanism of gene expression, genome stability, and development. DNA methylation modifications relate to effective induc-tion of defense responses for plant priming. In the Green Deal era, using plant defense inducers, compounds that activate defense and prime plants against imminent patho-gens attacks, is a safe and environmentally sustainable approach to support plants against pathogens. Here, salicylic acid loaded in chitosan nanoparticles, influenced hypomethylation on specific genomic regions that corresponded to defense-related genes, such as pectin lyases, defensins and leucine-rich repeat transmembrane protein kinases against the biotrophic fungal pathogen Podosphaera xanthii. A genomic region of the promoter of SKP1A, a core member of the SCF E3 ubiquitin ligase complex, was found to be a significantly hypomethylated DMR. Examination of this DMR revealed the presence of salicylic acid-, auxin-, and defense-related cis-elements. Investigation of proteins associated with the above cis-elements showed significant expression upreg-ulation after salicylic acid application. Moreover, association of the identified DMR with transcriptomics showed significant enrichment of the salicylic acid pathway. Overall, these findings shed light on the epigenetic mechanisms that underly salicylic acid- re-lated defense priming in plants.