Epitranscriptomic RNA editing resolves Mus81 DNA repair tradeoffs in heat tolerance and meiosis

Maintaining genome integrity is essential, yet how DNA repair is balanced across life stages remains poorly understood. Here we uncover an epitranscriptomic mechanism in the fungal pathogen Fusarium graminearum that alleviates a trade-off between heat-stress adaptation and sexual reproduction. We show that FgMus81 acts independently of its nuclease activity and canonical partner FgMms4, and has dosage-dependent, stage-specific functions: restrained levels support meiosis, whereas elevated levels promote heat-stress survival. We identify a sexual stage-specific A-to-I RNA editing event that recodes FgMus81 (N420D) and tunes its abundance to meet meiotic demands without compromising stress resilience. Notably, both pre-editing and post-editing isoforms support meiotic interhomolog crossovers, but the post-editing isoform impairs mitotic recombination. Conservation of this editing across Sordariomycetes suggests evolutionary selection for stage-specific control. Together, these findings reveal an epitranscriptomic switch that partitions Mus81 functions across life stages and identify adaptive RNA editing as a regulator of homologous recombination in fungal pathogens.