DRUSE

Liudmila Chelysheva and colleagues studied BLAP75/Rmi1 in relation to BLM/Sgs1 and TopoIIIα/Top3. Their paper appeared on the December 2008 issue of PLoS Genetics journal. Below is the summary:

“Recombination is a process by which cells can repair DNA damage. Such repair can either be crossovers (CO), in which DNA molecules are submitted to major exchanges, or non-crossover (NCO) events. Eukaryotic cells have developed several mechanisms to maintain genome stability during vegetative development by limiting the occurrence of CO events in favour of NCO. BLAP75/Rmi1, BLM/Sgs1, and TopoIIIα/Top3 act together in a complex (BTB/RTR) known to be a crucial component of regulation mechanisms against CO formation. However, CO/NCO regulation is thought to be very different during meiosis since homologous chromosomes (paternal and maternal) overcome at least one CO/pair. In this study, we investigate the role of the BTB/RTR complex during meiotic recombination through the analysis of a function of one of its members: the A. thaliana homologue of BLAP75/Rmi1. We show for the first time that BLAP75/Rmi1 is also a key protein of the meiotic homologous recombination machinery. In Arabidopsis, we found that this protein is dispensable for homologous chromosome recognition and synapsis, but necessary for the repair of meiotic double-strand breaks. Furthermore, in the absence of BLAP75, bivalent formation can happen even in the absence of CO.”

Chelysheva L, Vezon D, Belcram K, Gendrot G, Grelon M. 2008. The Arabidopsis BLAP75/Rmi1 Homologue Plays Crucial Roles in Meiotic Double-Strand Break Repair. PLoS Genet 4(12): e1000309. doi:10.1371/journal.pgen.1000309

Note: A. thaliana blap75 mutants are sterile. They examined the reproductive development of these mutants and found that blap75 sterility is due to abortion of male and female gametophytes. In particular, blap75 mutants show defects in male sporogenesis.