Ph2 encodes the mismatch repair protein MSH7-3D that inhibits wheat homoeologous recombination

Abstract

Meiotic recombination is a critical process for plant breeding, as it creates novel allele
combinations that can be exploited for crop improvement. In wheat, a complex allohexaploid
that has a diploid-like behaviour, meiotic recombination between homoeologous or alien
chromosomes is suppressed through the action of several loci. Here, we report positional
cloning of Pairing homoeologous 2 (Ph2) and functional validation of the wheat DNA mismatch
repair protein MSH7-3D as a key inhibitor of homoeologous recombination, thus solving a
half-century-old question. Similar to ph2 mutant phenotype, we show that mutating MSH7-
3D induces a substantial increase in homoeologous recombination (up to 5.5 fold) in wheatwild
relative hybrids, which is also associated with a reduction in homologous recombination.
These data reveal a role for MSH7-3D in meiotic stabilisation of allopolyploidy and provides
an opportunity to improve wheat’s genetic diversity through alien gene introgression, a major
bottleneck facing crop improvement.