Does Ph1 in Wheat Reveal the Universal Regulator of Pairing and Recombination?

Despite possessing multiple sets of related chromosomes, hexaploid (bread) and tetraploid (pasta) wheat, both behave as diploids at meiosis. The Ph1 locus in wheat ensures correct chromosome pairing and recombination between the related chromosomes in wheat.  We have shown that: Ph1 is defined to a kinase locus carrying a segment of heterochromatin; Ph1 alters meiotic phosphorylation levels; Ph1 promotes correct pairing of centromeres; Ph1 promotes correct pairing of chromosome arms; Ph1 regulates the conversion of MLH1 sites to crossover; and the ratio of MLH1 sites to crossover is closer to 1:1 in healthy wheat hybrids. Essentially Ph1 has two distinct effects, regulating when the chromosomes become  competent to pair during the telomere bouquet, and the ability of Double Holliday Junctions formed between diverged chromosomes to resolve as crossovers at the MLH1 complex stage. Consistent with this, initial studies indicate that key factors involved in initiating double strand break repair early in meiosis, and involved with the MLH1 complex, show altered phosphorylation with and without Ph1.  Interestingly a recent C elegans study has also concluded that meiotic phosphorylation levels: promotes correct pairing of centromeres; promotes correct pairing of chromosome arms; regulates the conversion of MLH1 sites to crossovers; and at increased phosphorylation levels, ratio of MLH1 sites to crossover is closer to 1:1 in healthy worms. Therefore phosphorylation may be the universal regulator of correct meiotic chromosome pairing and recombination.