Molecular cloning and characterization of RAD51-like genes from Arabidopsis thaliana

Homologous recombination is an essential process for the maintenance and variability of the genome. In eukaryotes, the Rad52 epistasis group proteins serve the main role for meiotic recombination and/or homologous recombinational repair. Rad51-like proteins, such as Rad55 and Rad57 in yeast, play a role in assembly or stabilization of multimeric Rad51 that promotes homologous pairing and strand exchange reactions. We cloned two RAD51-like genes named AtXRCC3 and AtRAD51C from Arabidopsis thaliana. Both AtXRCC3 and AtRAD51C expressed two alternatively spliced transcripts, and AtRAD51C produced two different sizes of isoforms, a long (AtRAD51Cα) and a short one (AtRAD51Cβ). The predicted protein sequences of these genes showed characteristic features of the RecA/Rad51 family; especially the amino acids around the ATP-binding motifs were well conserved. The transcripts of AtXRCC3 and AtRAD51C were detected in various tissues, with the highest level of expression in flower buds. Expression of both genes was induced by γ-ray irradiation. The results of yeast two-hybrid assays suggested that Arabidopsis Rad51 family proteins form a complex, which could participate in meiotic recombination and/or homologous recombinational repair.