The innate immune system is an evolutionarily conserved general defense strategy of almost all higher organisms, including plants and animals. This defense mechanism is inscribed in their genes and allows them to recognize and defend against attackers. Moreover, invertebrates have evolved an additional, adaptive immune system based on antibody production.
In the past, we focused our research on the plant defense system. Pathogen recognition induce in the activation of signaling pathways that include metabolic changes, phosphorylation reactions, the production of reactive oxygen and nitrogen species and finally result in defense response. Moreover, plants have developed a priming system, whereby they memorize previous infections and can respond more robustly to subsequent pathogen challenges. There is already clear evidence that epigenetic mechanisms, like DNA methylation and histone modifications, directly participate in plant immune memory.