Dna Repair Mechanism Suppresses Gene Transfer From Plastids To Nucleus In Plants

A new study in Nature Plants reveals a mechanism in plants that suppresses DNA transfer from plastids to the nucleus. The research, led by Gonzalez-Duran, Kroop, Schadach, and colleagues, shows that DNA double-strand break (DSB) repair machinery plays a key role in preventing this transfer. Plastids, originating from cyanobacteria, have transferred many genes to the nucleus during evolution. The study finds that plants use DSB repair pathways to prevent excessive plastid DNA incorporation, maintaining nuclear genome integrity. The researchers demonstrated that canonical DSB repair components minimize foreign DNA integration when DNA damage occurs near potential plastid DNA insertion sites. Plants with compromised DSB repair pathways showed increased plastid DNA integration, genomic instability, and aberrant gene expression patterns. Advanced genomic sequencing techniques showed frequent plastid DNA fragments infiltrating the nucleus. However, stable integration events into nuclear chromosomes are suppressed by the DSB repair system. The study found that recognition signals and protein complexes assemble selectively at DSB sites, without accommodating plastid-derived DNA fragments as repair substrates. This selectivity may involve sequence-context recognition and chromatin architecture. The findings suggest that DNA repair pathways act as gatekeepers controlling the acceptance of exogenous organellar sequences. Engineering plants with modulated DSB repair capabilities could influence plastid DNA introgression rates, offering a tool for genome editing and synthetic biology. This research highlights the importance of DNA repair mechanisms in maintaining genomic integrity and regulating genome evolution in eukaryotic cells. It also prompts a reevaluation of horizontal gene transfer estimates in plant genomes.