MITOCHONDRIAL GENOME RECOMBINATION AND REPAIR IN PLANT SOMATIC HYBRIDS

LAURA EVANGELINA GARCIA; GANDINI, CAROLINA L; MARIA VIRGINIA SANCHEZ PUERTA

Mendoza

Congreso; LVIII Annual Meeting of the Argentine Society for Biochemistry and Molecular Biology Research; 2022

SAIB

Recombination and repair of plant mitochondrial genomes are not well understood. Several re-combination pathways have beeninferred in studies of Arabidopsis mutants of nuclear factors involved in mitochondrial recombination surveillance. Somatic hybridsbetween phylogenetically distant species offer a remarkable model to study mitochondrial genome recombination in wild typeplants. Previously, we reported highly chimeric mitogenomes in two somatic hybrids between the Solanaceae Nicotiana tabacum and Hyoscyamus niger unrevealing that most rearrangements occurred by homologous re-combination and that similar regionscontributed by both parents are preferentially lost. However, the number of recombination events inferred from assembled plantmitogenomes is underestimated be-cause only a subset of the co-existing genomic and subgenomic arrangements are represented.In this study, we developed a bioinformatic pipeline that infers recombination events by analyzing mapping patterns and genotypeswitches using paired-end read information without assembling the mitogenome. We analyzed the recombination map of a somatichybrid produced by chemical protoplast fusion be-tween N. tabacum and another Solanaceae, Physochlaina orientalis and re-analyzed the two somatic hybrids between tobacco and H. niger. We identified between 45 and 107 homologous recombination(HR) events in the hybrids. We were also able to infer the molecular mechanism of HR and found that the majority involved theBreak-induced Replication (BIR) pathway. Interestingly, the information offered by the paired end reads showed that independentevents frequently occur in the same regions of the recombining tracts within and across somatic hybrids, suggesting the existenceof recombination hotspots in plant mitogenomes. In addition, three non-homologous recombination events were also detected intwo of the hybrid mitochondria. In conclusion, BIR is the main pathway of mitogenomes replication/recombination followingprotoplast fusion in somatic hybrids. In addition, the somatic hybrid model presumably mimics the process after foreignmitochondria enter the host cell, suggesting that foreign DNA is integrated in plant mitogenomes through this pathway