Post-translational modifications in priming the plant immune system: ripe for exploitation?

Microbes constantly challenge plants, and some can successfully infect their host and cause disease. Basal immunity against plant pathogens in many cases is not enough for survival and leads to disease and, ultimately, a premature death of the host plant. However, the plant immune system can be temporarily and even transgenerationally primed; this 'primed state' leads to changes in the plant involving transcriptional, post-translational, metabolic, physiological and epigenetic reprogramming, which enables fine-tuning defence mechanisms for a rapid and/or more robust response after abiotic and/or biotic stress. This can ultimately affect pathogen infection speed and, hence, decrease its ability to overcome host resistance and the final outcome of the host-pathogen interaction. The role of the three major post-translational modifications (PTMs) (protein ubiquitination, phosphorylation and SUMOylation) in plant immunity has been well established. However, the role of PTMs on defence priming, and how the PTM machinery is affected in primed plants and its connection to plant resistance against biotic/abiotic stress is not well understood. This Review highlights the current state of play of priming-mediated post-translational reprogramming and explores new areas for future research.