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 wheat-wild 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.
Highlights
Meiotic recombination is a critical process for plant breeding, as it creates novel allele combinations that can be exploited for crop improvement
Based on the analysis of a set of created 3DS deletion mutants[23] combined with exome sequencing and transcriptome analysis of ph2a and ph2b mutants versus wild-type, we identify TaMSH7-3D, a gene encoding a plant specific DNA mismatch repair protein
Using independent ethyl methanesulfonate (EMS) generated msh7-3D mutants crossed with wheat wild relative Aegilops variabilis, we demonstrate that msh7-3D mutants recapitulate the ph[2] phenotype with a highly significant (5.5-fold) increase in homoeologous recombination and a reduction in homologous recombination
Summary
Meiotic recombination is a critical process for plant breeding, as it creates novel allele combinations that can be exploited for crop improvement. Similar to ph[2] mutant phenotype, we show that mutating MSH73D induces a substantial increase in homoeologous recombination (up to 5.5 fold) in wheatwild relative hybrids, which is 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. Subsequent physical mapping localised Ph1 to a 2.5 Mbp region on chromosome 5BL15 This region contains a meiotic gene ZIP4 and a heterochromatin tandem repeat block, inserted within a cluster of CDK2-like genes[15,16,17,18]. The exact mode of action is unknown, TaZIP4-B2 seems to act as a focal point, facilitating physical interactions between components of the chromosome axis and crossover machinery[17]
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