Disruption of the Arabidopsis RAD50 gene leads to plant sterility and MMS sensitivity

Abstract

Summary The Rad50 protein is involved in the cellular response to DNA‐double strand breaks (DSBs), including the detection of damage, activation of cell‐cycle checkpoints, and DSB repair via recombination. It is essential for meiosis in yeast, is involved in telomere maintenance, and is essential for cellular viability in mice. Here we present the isolation, sequence and characterization of the Arabidopsis thaliana RAD50 homologue (AtRAD50) and an Arabidopsis mutant of this gene. A single copy of this gene is present in the Arabidopsis genome, located on chromosome II. Northern analysis shows a single 4.3 Kb mRNA species in all plant tissues tested, which is strongly enriched in flowers and other tissues with many dividing cells. The predicted protein presents strong conservation with the other known Rad50 homologues of the amino‐ and carboxy‐terminal regions. Mutant plants present a sterility phenotype which co‐segregates with the T‐DNA insertion. Molecular analysis of the mutant plants shows that the sterility phenotype is present only in the plants homozygous for the T‐DNA insertion. An in vitro mutant cell line, derived from the mutant plant, shows a clear hypersensitivity to the DNA‐damaging agent methylmethane sulphonate, suggesting a role of RAD50 in double‐strand break repair in plant cells. This is the first report of a plant mutated in a protein of the Rad50–Mre11–Xrs2 complex, as well as the first data suggesting the involvement of the Rad50 homologue protein in meiosis and DNA repair in plants.

ASK1, a SKP1 homolog, is required for nuclear reorganization, presynaptic homolog juxtaposition and the proper distribution of cohesin during meiosis in Arabidopsis

“…Particularly, recent experiments using Arabidopsis as a model system have provided considerable new insights into recombination events in plants. For example, homologs of genes known to be required for meiotic recombination, such as DMC1, MER3/RCK, MRE11, MSH4, RAD50, RAD51, RAD51C, SPO11, and XRCC3, have been identified in Arabidopsis (Azumi et al 2002;Bleuyard 2004;Bundock and Hooykaas 2002;Chen et al 2005;Couteau et al 1999;Doutriaux et al 1998;Gallego et al 2001;Grelon et al 2001;Hartung and Puchta 2000;Higgins et al 2004;Li et al 2005;Mercier et al 2005). Several Arabidopsis homologs of proteins that are necessary for the establishment of cohesion and possibly SC formation have also been identified.…”

Defects in nucleolar migration and synapsis in male prophase�I in the ask1-1 mutant of Arabidopsis

“…These proteins are either components of early recombination nodules, such as Rad50, Mre11, Rad51, Dmc1 (Bishop 1994;Anderson et al 1997;Stassen et al 1997;Doutriaux et al 1998;Plug et al 1998;Couteau et al 1999;Franklin et al 1999;Gallego et al 2001;Daoudal-Cotterell et al 2002;Moens et al 2002), or components of SCs (Roeder 1997), or other chromosomeassociated proteins such as sister-chromatid cohesins (Nasmyth 2001;Cai et al 2003), Twi1 (Mercier et al 2001), and ASY1 (Armstrong et al 2002). However, nonstructural proteins of meiotic chromosomes that may be involved in regulation of nucleolar migration and the process of chromosome synapsis have not yet been described.…”

Arabidopsis Rad51B is important for double-strand DNA breaks repair in somatic cells

“…In contrast to yeast and vertebrates, there is less information on HR in higher plants, although the completion of the Arabidopsis genome sequence suggests the existence of almost all the Rad52 pathway members including the five Rad51 paralogs seen in vertebrates, and some of them have been cloned and characterized with their mutant plants (Gallego et al, 2001;Bundock and Hooykaas, 2002;Bleuyard and White, 2004;Li et al, 2004;Puizina et al, 2004). In this regard, all knockout type mutants show higher sensitivity to genotoxic stresses, and importantly, sterile phenotypes.…”