Poster: Reproductive development

Abs # 377: Increased homoeologous recombination and microsatellite instability in a msh2 mutant in Arabidopsis thaliana.

Presenter:	Jean, Martine , mjean@rsvs.ulaval.ca
Authors	Jean, Martine  (A)   Li, Liang Liang  (A)   Azaiez, Aïda  (A)   Belzile, François  (A)
Affiliations:	(A): Université Laval,Plant Science Department

Eukaryotic cells rely on various DNA repair systems to ensure the maintenance of genetic information. As plants do not establish a germinal lineage until late during development, somatic mutations can easily be passed on to subsequent generations if they are not repaired. In addition to its role in post-replicative DNA repair, the DNA mismatch repair (MMR) system is also involved in regulating recombination between homoeologous sequences. This role in recombination is thought to involve recombination intermediates harboring mismatched bases. With the aim of deciphering the role of the MMR system in recombination and genetic stability in Arabidopsis thaliana, we are investigating the function of AtMSH2, a key component of the MMR system. To achieve this goal, we developed GUS-based reporter systems to easily monitor recombination (both homologous and homoeologous) as well as microsatellite instability. These tools were used to characterize a mutant carrying a T-DNA insertion allele of the AtMSH2 gene. A several-fold increase in the frequency of homoeologous recombination events (visualized as blue sectors) was observed in the mutant. A marked increase in the frequency of germinally-transmitted mutations in G₇ and G₁₆ synthetic microsatellites was also observed. The fixation of new alleles at various genomic microsatellites was also noted following serial propagation of msh2 lines. Our results thus support a crucial role for the MMR system in ensuring genome stability during sexual reproduction in plants.