Epigenetic control of defense genes following MeJA-induced priming in rice (O. sativa)

In plant defense, priming is a physiological process by which a plant prepares to more quickly or aggressively respond to a future biotic or abiotic stress. This unique physiological state can be induced by beneficial microbes or by treatment with natural or synthetic compounds. Priming has been described copiously, mainly in dicots, but the study on the molecular mechanisms regulating the phenomenon is still at its infancy. A fascinating possibility is that epigenetic changes may be the main actors on priming establishment. A more accessible chromatin structure, due to DNA methylation and/or histone modifications, could facilitate a quicker and more potent gene response to a subsequent attack. Here, we investigated the impact of methyl jasmonate (MeJA)-induced priming on the response efficacy to mechanical wounding of a monocot (Oryza sativa). In particular, we showed that MeJA primes plants for increased expression of defense-related genes, such as OsBBPI and OsPOX, upon wounding. Finally, we provided evidence that MeJA modulates histone modifications in the promoter region of OsBBPI, as well as changes at genome-wide DNA methylation level. Together these studies corroborate the importance of priming in strengthening plant defense and support the growing evidence that epigenetic regulation plays a pivotal role in priming onset.