E. Sánchez-Morán and J.L. Santos acted as joint senior authors.
Together yes, but not coupled: new insights into the roles of RAD51 and DMC1 in plant meiotic recombination
Article first published online: 15 DEC 2011
© 2011 The Authors. The Plant Journal © 2011 Blackwell Publishing Ltd
The Plant Journal
Volume 69, Issue 6, pages 921–933, March 2012
How to Cite
Pradillo, M., López, E., Linacero, R., Romero, C., Cuñado, N., Sánchez-Morán, E. and Santos, J. L. (2012), Together yes, but not coupled: new insights into the roles of RAD51 and DMC1 in plant meiotic recombination. The Plant Journal, 69: 921–933. doi: 10.1111/j.1365-313X.2011.04845.x
- Issue published online: 16 MAR 2012
- Article first published online: 15 DEC 2011
- Accepted manuscript online: 8 NOV 2011 09:46AM EST
- Received 20 July 2011; revised 1 November 2011; accepted 2 November 2011; published online 15 December 2011.
- homologous recombination;
- DSB repair;
The eukaryotic recombinases RAD51 and DMC1 are essential for DNA strand-exchange between homologous chromosomes during meiosis. RAD51 is also expressed during mitosis, and mediates homologous recombination (HR) between sister chromatids. It has been suggested that DMC1 might be involved in the switch from intersister chromatid recombination in somatic cells to interhomolog meiotic recombination. At meiosis, the Arabidopsis Atrad51 null mutant fails to synapse and has extensive chromosome fragmentation. The Atdmc1 null mutant is also asynaptic, but in this case chromosome fragmentation is absent. Thus in plants, AtDMC1 appears to be indispensable for interhomolog homologous recombination, whereas AtRAD51 seems to be more involved in intersister recombination. In this work, we have studied a new AtRAD51 knock-down mutant, Atrad51-2, which expresses only a small quantity of RAD51 protein. Atrad51-2 mutant plants are sterile and hypersensitive to DNA double-strand break induction, but their vegetative development is apparently normal. The meiotic phenotype of the mutant consists of partial synapsis, an elevated frequency of univalents, a low incidence of chromosome fragmentation and multivalent chromosome associations. Surprisingly, non-homologous chromosomes are involved in 51% of bivalents. The depletion of AtDMC1 in the Atrad51-2 background results in the loss of bivalents and in an increase of chromosome fragmentation. Our results suggest that a critical level of AtRAD51 is required to ensure the fidelity of HR during interchromosomal exchanges. Assuming the existence of asymmetrical DNA strand invasion during the initial steps of recombination, we have developed a working model in which the initial step of strand invasion is mediated by AtDMC1, with AtRAD51 required to check the fidelity of this process.