Involved in meiotic recombination in association with MSH5. Required for reciprocal recombination and proper segregation of homologous chromosomes at meiosis. Promotes homologous recombination through facilitating chiasma formation during prophase I. Involved in the control of class I crossovers formation. In pollen mother cells during meiosis, localizes to unsynapsed axes during leptotene and zygotene, but is not present on synapsed regions of zygotene nuclei. Specifically expressed in flowers. Normal vegetative growth but severe reduction in fertility due to a decrease in chiasma frequency at metaphase I of meiosis. Belongs to the DNA mismatch repair MutS family.