Suppression of Repeat-Mediated Gross Mitochondrial Genome Rearrangements by RecA in the Moss Physcomitrella patens    

Abstract

RecA and its ubiquitous homologs are crucial components in homologous recombination. Besides their eukaryotic nuclear counterparts, plants characteristically possess several bacterial-type RecA proteins localized to chloroplasts and/or mitochondria, but their roles are poorly understood. Here, we analyzed the role of the only mitochondrial RecA in the moss Physcomitrella patens. Disruption of the P. patens mitochondrial recA gene RECA1 caused serious defects in plant growth and development and abnormal mitochondrial morphology. Analyses of mitochondrial DNA in disruptants revealed that frequent DNA rearrangements occurred at multiple loci. Structural analysis suggests that the rearrangements, which in some cases were associated with partial deletions and amplifications of mitochondrial DNA, were due to aberrant recombination between short (<100 bp) direct and inverted repeats in which the sequences were not always identical. Such repeats are abundant in the mitochondrial genome, and interestingly many are located in group II introns. These results suggest that RECA1 does not promote but rather suppresses recombination among short repeats scattered throughout the mitochondrial genome, thereby maintaining mitochondrial genome stability. We propose that RecA-mediated homologous recombination plays a crucial role in suppression of short repeat-mediated genome rearrangements in plant mitochondria.

Cost of Having the Largest Mitochondrial Genome: Evolutionary Mechanism of Plant Mitochondrial Genome

“…Journal of Botany 5 in Physcomitrella results in the activation of mitochondrial genome recombinations involving repeats of less than 100 bp [55]. In the presence of functional Msh1, recombination via short repeats is apparently suppressed, but recombinant DNA molecules are not completely absent; they can be present at very low stoichiometric levels as sublimons.…”

Crystal Structures of DNA-Whirly Complexes and Their Role in Arabidopsis Organelle Genome Repair

“…DNA rearrangements are listed in Supplemental Data Set 1 online. plant mitochondria (Mackenzie, 2005;Maré chal and Brisson, 2010;Woloszynska, 2010) and is modulated by a variety of proteins involved in maintaining mitochondrial genome stability, such as OSB1 (Zaegel et al, 2006), RecA3 (Shedge et al, 2007), RecA1 (Odahara et al, 2009), and Msh1 (Abdelnoor et al, 2003). DNA from wild-type, why2-1, and why1 why3 plants were analyzed by DNA gel blot and probed with mitochondrial repeats as described by Arrieta-Montiel et al (2009).…”

“…Their maintenance is thus mainly ensured by nuclear-encoded DNA replication, recombination, and repair proteins that are targeted to plastids and/or mitochondria. In recent years, some of these proteins have been identified, including the Arabidopsis thaliana and Physcomitrella patens RecA homologs (Shedge et al, 2007;Odahara et al, 2009), the Arabidopsis MutS-like MSH1 (Abdelnoor et al, 2003), the Arabidopsis organelle single-stranded DNA binding protein OSB1 (Zaegel et al, 2006), and the plastid-targeted Whirlies of Arabidopsis and maize (Zea mays) (Maré chal et al, 2009).…”

Origin of the CMS gene locus in rapeseed cybrid mitochondria: Active and inactive recombination produces the complex CMS gene region in the mitochondrial genomes of Brassicaceae

“…In Arabidopsis, Msh1 suppresses recombination via short repeat sequences ranging in size from 108 to 556 bp, while shorter repeats of less than 108 bp do not respond to Msh1 (Arrieta-Montiel et al, 2009). On the other hand, RecA1 functions as a suppressor of recombination involving repeats of less than 100 bp in Physcomitrella (Odahara et al, 2009). The size of R2 (143 bp) is within the size that Msh1 can mediate recombination (from 108 to 556 bp), while R3 (63 bp) may be a target of RecA1 regulation (less than 100 bp).…”