A DNA mismatch repair gene links to the Ph2 locus in wheat.

DNA mismatch repair is an essential system for maintaining genetic stability in bacteria and higher eukaryotes. Based on the conserved regions of the bacterial MutS gene and its homologues in yeast and human, a wheat cDNA homologue of MSH6, designated TaMSH7, was isolated by RT-PCR. The deduced amino acid sequence of TaMSH7 shows conserved domains characteristic of other MSH6 genes, with highest similarity to maize MSH7 and Arabidopsis MSH7. TaMSH7 is expressed in meristem tissue associated with a high level of mitotic and meiotic activity, with maximum expression in the reproductive organs of young flower spikes. TaMSH7 is located on the short arms of chromosomes 3A, 3B, and 3D and has been mapped within barley chromosome 3HS. The copy on 3DS is located within the region deleted in the wheat mutant ph2a, which shows altered recombination frequency in the interspecific hybrids. The relationship between the ph2a mutant and TaMSH7 gene function is discussed.