Abstract: The invention relates to isolated nucleic acid molecules encoding MutS homologues (MSHs). Such MSH proteins are involved in DNA mismatch-repair processes in organisms. The invention provides isolated nucleic acid molecules comprising MSH2 nucleotide sequences which encode MSH2 proteins and MSH2 nucleotide sequences which encode dominant-negative MSH2 variants. Such MSH2 nucleotide sequences find use in altering mismatch repair, mutation rates and recombination frequencies in both eukaryotic and prokaryotic organisms. The invention also provides isolated nucleic acid molecules comprising MSH2 promoter nucleotide sequences. Such MSH2 promoter nucleotide sequences find use in regulating the expression of genes of interest in plants. Additionally provided are isolated proteins, transformed host cells, and transformed plants, tissues, cells and seeds thereof.