title: Reduction of stability of arabidopsis genomic and transgenic DNA-repeat sequences (microsatellites) by inactivation of AtMSH2 mismatch-repair function.
abstract: Highly conserved mismatch repair (MMR) systems promote genomic stability by correcting DNA replication errors, antagonizing homeologous recombination, and responding to various DNA lesions. Arabidopsis and other plants encode a suite of MMR protein orthologs, including MSH2, the constant component of various specialized eukaryotic mismatch recognition heterodimers. To study MMR roles in plant genomic stability, we used Arabidopsis AtMSH2::TDNA mutant SALK_002708 and AtMSH2 RNA-interference (RNAi) lines. AtMSH2::TDNA and RNAi lines show normal growth, development, and fertility. To analyze AtMSH2 effects on germ line DNA fidelity, we measured insertion-deletion mutation of dinucleotide-repeat sequences (microsatellite instability) at nine loci in 16 or more progeny of two to four different wild-type or AtMSH2-deficient plants. Scoring 992 total alleles revealed 23 (2.3%) unique and 51 (5.1%) total repeat length shifts ([+2], [-2], [+4], or [-4] bp). For the six longest repeat loci, the corresponding frequencies were 22/608 and 50/608. Two of four AtMSH2-RNAi plants showed similar microsatellite instability. In wild-type progeny, only one unique repeat length allele was found in 576 alleles tested. This endogenous microsatellite instability, shown for the first time in MMR-defective plants, is similar to that seen in MMR-defective yeast and mice, indicating that plants also use MMR to promote germ line fidelity. We used a frameshifted reporter transgene, (G)(7)GUS, to measure insertion-deletion reversion as blue-staining beta-glucuronidase-positive leaf spots. Reversion rates increased only 5-fold in AtMSH2::TDNA plants, considerably less than increases in MSH2-deficient yeast or mammalian cells for similar mononucleotide repeats. Thus, MMR-dependent error correction may be less stringent in differentiated leaf cells than in plant equivalents of germ line tissue.
authors.affiliation: Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, OR 97331-7301, USA.
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Leonard
authors.forename: Stephanie R
authors.initials: SR
authors.lastname: Bollmann
authors.forename: John B
authors.initials: JB
authors.lastname: Hays
mesh_terms: D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D020137:Base Pair Mismatch / Q000235:genetics; D004260:DNA Repair; D004269:DNA, Bacterial / Q000235:genetics; D018745:Genome, Plant; D042822:Genomic Instability / Q000235:genetics; D005966:Glucuronidase / Q000235:genetics / Q000378:metabolism; D051718:MutS Homolog 2 Protein; D009154:Mutation; D030821:Plants, Genetically Modified; D034622:RNA Interference; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D019076:Transgenes / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D004269:DNA, Bacterial; C036483:T-DNA; D005966:Glucuronidase; C108984:MSH2 protein, Arabidopsis; D051718:MutS Homolog 2 Protein