RecA-Dependent DNA Repair Results in Increased Heteroplasmy of the Arabidopsis Mitochondrial Genome    

Abstract

Plant mitochondria have very active DNA recombination activities that are responsible for its plastic structures and that should be involved in the repair of double-strand breaks in the mitochondrial genome. Little is still known on plant mitochondrial DNA repair, but repair by recombination is believed to be a major determinant in the rapid evolution of plant mitochondrial genomes. In flowering plants, mitochondria possess at least two eubacteria-type RecA proteins that should be core components of the mitochondrial repair mechanisms. We have performed functional analyses of the two Arabidopsis (Arabidopsis thaliana) mitochondrial RecAs (RECA2 and RECA3) to assess their potential roles in recombination-dependent repair. Heterologous expression in Escherichia coli revealed that RECA2 and RECA3 have overlapping as well as specific activities that allow them to partially complement bacterial repair pathways. RECA2 and RECA3 have similar patterns of expression, and mutants of either display the same molecular phenotypes of increased recombination between intermediate-size repeats, thus suggesting that they act in the same recombination pathways. However, RECA2 is essential past the seedling stage and should have additional important functions. Treatment of plants with several DNA-damaging drugs further showed that RECA3 is required for different recombination-dependent repair pathways that significantly contribute to plant fitness under stress. Replication repair of double-strand breaks results in the accumulation of crossovers that increase the heteroplasmic state of the mitochondrial DNA. It was shown that these are transmitted to the plant progeny, enhancing the potential for mitochondrial genome evolution.

Mechanism of Homologous Recombination and Implications for Aging-Related Deletions in Mitochondrial DNA

“…Heterologous expression of RECA2 and RECA3 partially complements E. coli mutants defective in DNA repair. Interestingly, loss of the RecA3 function in Arabidopsis thaliana mitochondria increases rather than suppresses mtDNA rearrangements and recombination between intermediate-size repeats (154,155). Suppression of repeat-mediated genome rearrangements by a RecA ortholog has also been shown in the mitochondria of Physcomitrella patens (156).…”

“…These proteins are speculated to participate in mtDNA repair especially under DNA-damaging conditions (152)(153)(154). Heterologous expression of RECA2 and RECA3 partially complements E. coli mutants defective in DNA repair.…”

Arabidopsis Seed Mitochondria Are Bioenergetically Active Immediately upon Imbibition and Specialize via Biogenesis in Preparation for Autotrophic Growth

“…The thermocycling program was as follows: 7 min denaturing step at 95°C, then 40 cycles of 10 s at 95°C and 45 s at 60°C. To quantify DNA quality, sets of primers were used to amplify either long fragments or short fragments of the mitochondrial or nuclear genomes as described by Miller-Messmer et al (2012).…”

The Mitochondrial DNA (mtDNA)-Associated Protein SWIB5 Influences mtDNA Architecture and Homologous Recombination

“…These crossovers can be either reciprocal, if both recombination products accumulate at similar levels, or asymmetrical, if one of both crossovers is preferred. The accumulation of these infrequent recombination (IR) products results in the presence of different variants of the mitochondrial genome within a cell or an individual, termed the heteroplasmic state of the genome (Miller-Messmer et al, 2012). Homologous proteins of eubacterial factors involved in HR have been shown to have a role in mtDNA recombination (Miller-Messmer et al, 2012;Wallet et al, 2015).…”