Utility of in vitro culture to the study of plant mitochondrial genome configuration and its dynamic features

Recombination activity plays an important role in the heteroplasmic and stoichiometric variation of plant mitochondrial genomes. Recent studies show that the nuclear gene MSH1 functions to suppress asymmetric recombination at 47 repeat pairs within the Arabidopsis mitochondrial genome. Two additional nuclear genes, RECA3 and OSB1, have also been shown to participate in the control of mitochondrial DNA exchange in Arabidopsis. Here, we demonstrate that repeat-mediated de novo recombination is enhanced in Arabidopsis and tobacco mitochondrial genomes following passage through tissue culture, which conditions the MSH1 and RECA3 suppressions. The mitochondrial DNA changes arising through in vitro culture in tobacco were reversible by plant regeneration, with correspondingly restored MSH1 transcript levels. For a growing number of plant species, mitochondrial genome sequence assembly has been complicated by insufficient information about recombinationally active repeat content. Our data suggest that passage through cell culture provides a rapid and effective means to decipher the dynamic features of a mitochondrial genome by comparative analysis of passaged and non-passaged mitochondrial DNA samples following next-generation sequencing and assembly.