Recombination and the maintenance of plant organelle genome stability

Abstract

SummaryLike their nuclear counterpart, the plastid and mitochondrial genomes of plants have to be faithfully replicated and repaired to ensure the normal functioning of the plant. Inability to maintain organelle genome stability results in plastid and ⁄ or mitochondrial defects, which can lead to potentially detrimental phenotypes. Fortunately, plant organelles have developed multiple strategies to maintain the integrity of their genetic material. Of particular importance among these processes is the extensive use of DNA recombination. In fact, recombination has been implicated in both the replication and the repair of organelle genomes. Revealingly, deregulation of recombination in organelles results in genomic instability, often accompanied by adverse consequences for plant fitness. The recent identification of four families of proteins that prevent aberrant recombination of organelle DNA sheds much needed mechanistic light on this important process. What comes out of these investigations is a partial portrait of the recombination surveillance machinery in which plants have co-opted some proteins of prokaryotic origin but have also evolved whole new factors to keep their organelle genomes intact. These new features presumably optimized the protection of plastid and mitochondrial genomes against the particular genotoxic stresses they face.

The Single-Stranded DNA-Binding Protein WHIRLY1 Represses WRKY53 Expression and Delays Leaf Senescence in a Developmental Stage-Dependent Manner in Arabidopsis

“…2); however, the exact functions of WHY3 are elusive in this regard. It is reported that double knockout of WHY1 and WHY3 (why1why3) results in plants with variegated green/white/yellow leaves, suggesting a protective function of WHY1 and WHY3 against microhomology-mediated break-induced replication events in chloroplasts (Maréchal et al, 2009;Cappadocia et al, 2010;Maréchal and Brisson, 2010). Therefore, WHY proteins might have different functions depending on intracellular localization and developmental stage.…”

“…This phenomenon is most likely a senescent phenotype. However, the why1why3 double mutant (ko1/3) line did not show any senescent phenotype, but it was reported that 5% variegation plants of the why1why3 line have the pale-green phenotype during seedling development (Maréchal et al, 2009;Cappadocia et al, 2010;Maréchal and Brisson, 2010).…”

“…8A). According to the ChIP-sequencing results (Supplemental Table S3) and based on previous reports that WHY1 could bind to the telomere sequence in the promoter of PR1 and that WHY1 had functions in the DNA repair of double-strand breaks (DSB; Desveaux et al, 2004;Yoo et al, 2007;Maréchal et al, 2009;Maréchal and Brisson, 2010), the PR1 promoter was selected as a positive candidate control. As such, WRKY53, WRKY33, and SPO11 were detected in each DNA sample (Fig.…”

“…In fact, it was proposed that plastidic WHY1 in maize (Zea mays) and barley both have functions in RNA processing and that the plastidic WHY proteins in Arabidopsis have a function as antirecombination proteins that could be involved in maintaining plastome DNA stability (Maréchal et al, 2008(Maréchal et al, , 2009Prikryl et al, 2008;Cappadocia et al, 2010;Maréchal and Brisson, 2010;Melonek et al, 2010).…”

Cool as the Cucumber Mitochondrial Genome: Complete Sequencing Reveals Dynamics of Recombination, Sequence Transfer, and Multichromosomal Structure

“…Plant mitochondrial genomes vary greatly in size, from ;200 kb to over 2 Mb, and are substantially larger than mitochondrial genomes of other eukaryotes (reviewed in Maré chal and Brisson, 2010). Physical mapping and sequencing of some of the smaller mitochondrial genomes show that their structure is shaped by active recombination, gene transfer to the nucleus, and other forces that remain unclear (reviewed in Woloszynska, 2010).…”