The Arabidopsis AtRAD51 gene is dispensable for vegetative development but required for meiosis

Abstract

The maintenance of genome integrity and the generation of biological diversity are important biological processes, and both involve homologous recombination. In yeast and animals, homologous recombination requires the function of the RAD51 recombinase. In vertebrates, RAD51 seems to have acquired additional functions in the maintenance of genome integrity, and rad51 mutations cause lethality, but it is not clear how widely these functions are conserved among eukaryotes. We report here a loss-of-function mutant in the Arabidopsis homolog of RAD51, AtRAD51. The atrad51-1 mutant exhibits normal vegetative and flower development and has no detectable abnormality in mitosis. Therefore, AtRAD51 is not necessary under normal conditions for genome integrity. In contrast, atrad51-1 is completely sterile and defective in male and female meioses. During mutant prophase I, chromosomes fail to synapse and become extensively fragmented. Chromosome fragmentation is suppressed by atspo11-1, indicating that AtRAD51 functions downstream of AtSPO11-1. Therefore, AtRAD51 likely plays a crucial role in the repair of DNA doublestranded breaks generated by AtSPO11-1. These results suggest that RAD51 function is essential for chromosome pairing and synapsis at early stages in meiosis in Arabidopsis. Furthermore, major aspects of meiotic recombination seem to be conserved between yeast and plants, especially the fact that chromosome pairing and synapsis depend on the function of SPO11 and RAD51.H omologous recombination and DNA-damage repair are fundamental biological processes found in all life forms. Homologous recombination plays a major role in both maintaining genome stability (DNA-damage repair) and the generation of genetic variability. Defects in DNA-damage repair generally lead to genome instability and are increasingly found to be associated with cancer in mammals. The active surveillance mechanisms that can recognize and precisely repair DNA damage to prevent the accumulation of errors are meanwhile thought to be intimately involved in the prevention of cancer and the delaying of aging (1, 2). Genes playing critical roles in homologous recombination are important for these processes.Homologous recombination has been intensively studied in budding yeast Saccharomyces cerevisiae, and a number of genes have been identified that function in this process. Some of these genes, including RAD51, were identified based on the hypersensitivity of their mutants to radiation (3). RAD51 and another yeast gene, DMC1, share significant sequence homology with the bacterial recA gene (4). Similar to the bacterial RecA protein, the yeast RAD51 protein acts in homology searching, DNA pairing, and strand exchange (5), activities important for both DNAdamage repair and meiosis. RAD51 homologs have been found in all eukaryotic organisms thus far and are well studied in the vertebrates human, mouse, and chicken. In contrast to yeast, the loss of RAD51 function is lethal in both chicken DT40 and mouse cells (4). These RAD51-deficient cells arrest dur...

Replication Protein A (RPA1a) Is Required for Meiotic and Somatic DNA Repair But Is Dispensable for DNA Replication and Homologous Recombination in Rice

“…Among these mutants, atrad50, atmre11, atrad51, atrad51c, and atxrcc3, which have defects in the repairing of AtSPO11-induced DSB, exhibited similar meiotic chromosome behaviors like asynaptic homologs and/or chromosome fragmentation (Bleuyard et al, 2004a;Bleuyard and White, 2004;Li et al, 2004Li et al, , 2005Puizina et al, 2004). The meiotic chromosome fragmentation could be suppressed by mutation in AtSPO11-1 (Bleuyard et al, 2004b;Li et al, 2004Li et al, , 2005Puizina et al, 2004), which provides a direct evidence that the origin of the DNA breaks in these mutants is the unrepaired DSBs generated by AtSPO11. However, the atspo11-1 mutation only partially rescues meiotic chromosome fragmentation in atspo11-1/atatr, atspo11-1/ atatm double mutants and the atspo11-1/atatr/atatm triple mutant (Culligan and Britt, 2008).…”

The plant‐specific CDKB 1‐ CYCB 1 complex mediates homologous recombination repair in Arabidopsis

“…T‐DNA insertion line cycb1;3 (pst15850) was obtained from the RIKEN collection (Yokohama, Japan) and cycb1;4 from the GABI‐KAT collection (Bielefeld, Germany) (Kleinboelting et al , 2012). The ku70 (Riha et al , 2002), wee1 (De Schutter et al , 2007), and rad51 (Li et al , 2004) mutants were described previously. The reporter line uidA/IC9C was used as described in Molinier et al (2004) and the pCDKB1;1:GUS line as in Boudolf et al (2004).…”

Arabidopsis RAD51C Gene Is Important for Homologous Recombination in Meiosis and Mitosis

“…Our previous results suggested that AtRad51C and AtXrcc3 act together and are involved in DNA repair and meiotic recombination. Recently, AtXRCC3 and AtRAD51 knockout mutants have been identified and characterized in Arabidopsis Li et al, 2004). atrad51 and atxrcc3 mutants developed normally in vegetative stage but showed male and female sterility, due to chromosome fragmentation after pachytene in both types of gametogenesis.…”