Loss of H3.1K27me1 in Arabidopsis confers resistance to Geminivirus by sequestering DNA repair proteins onto rDNA and defense-related genes

The H3 methyltransferases ATXR5 and ATXR6 deposit H3.1K27me1 to heterochromatin to prevent genomic instability and transposon reactivation. Here, we report that atxr5 atxr6 mutants displayed robust resistance to Geminivirus. The viral resistance correlated with activation of DNA repair pathways, but not with transposon reactivation or heterochromatin amplification. We identified RAD51 and RPA1A as partners of virus-encoded Rep protein. The two DNA repair proteins showed increased binding to heterochromatic regions and defense-related genes in atxr5 atxr6 vs wild type plants. Consequently, the proteins had reduced interactions to viral DNA in the mutant, thus hampering viral replication. Additionally, RAD51 recruitment to the host genome arose via BRCA1, HOP2 and CYCB1, and this recruitment was essential for viral resistance in atxr5 atxr6. Thus, Geminiviruses adapt to healthy plants by hijacking its DNA repairing pathways for replication, but the host could retain DNA repairing proteins via sacrificing its genome stability to suppress viral infection.