P-246 - Impact of Histone Modifications on Antiviral Defense and Viral Evolution in Plants

Epigenetics has been proposed as a potential memory mechanism for modulating plant immune responses, but its role in the context of viral infections is poorly explored. Our previous findings indicate that plant epigenetic pathways affect antiviral responses and modulate virus evolution, with histone modifications likely playing a significant role. To further explore the impact of histone modifications on antiviral response and virus evolvability, twelve Arabidopsis thaliana lines deficient in various histone modifications were infected with the turnip mosaic virus (TuMV; Potyvirus rapae). Potential epigenetic pathways involved in antiviral defense were identified, and interesting genotypes exhibiting activation or repression mark defects, in addition to wild-type plants, were selected for virus evolution experiments. After evolving TuMV for six passages, the infectivity of all evolved lineages was increased in a host genotype-dependent manner. Notably, a susceptible mutant deficient in activation marks selected for a less virulent virus strain, while a remarkably tolerant mutant defective in repression marks selected for a more virulent strain. These findings reveal the impact of epigenetic pathways on the host-virus arms race and highlight the potential of evolved viruses as tools to dissect molecular drivers of antiviral defense at transcriptomic and epigenomic levels.