Beneficial interactions between plant-roots and Trichoderma spp. lead to a local and systemic enhancement of the plant immune system through a mechanism known as priming of defenses. In recent reports, we outlined a repertoire of genes and proteins differentially regulated in distant tissues of maize plants previously inoculated with Trichoderma atroviride. To further investigate the mechanisms involved in the systemic activation of plant responses, we continued evaluating the regulatory aspects of a selected group of genes when priming is triggered in maize plants. We conducted a time-course expression experiment from the beginning of the interaction between T. atroviride and maize roots, along plant vegetative growth and during Colletotrichum graminicola leaf infection. In addition to gene expression studies, the levels of jasmonic and salicylic acid were determined in the same samples for a comprehensive understanding of the gene expression results. Lastly, chromatin structure and modification assays were designed to evaluate the role of epigenetic marks during the long-lasting activation of the primed state of maize plants. The overall analysis of the results allowed us to shed some light on the interplay between the phytohormones and epigenetic regulatory events in the systemic and long-lasting regulation of maize plant defenses after Trichoderma inoculation.
