| Summary: | Although most flowering plants are polyploid, little is known of how the meiotic process evolves after polyploidisation to stabilise and preserve fertility. On wheat polyploidisation, the major meiotic gene <i>ZIP4</i> on chromosome 3B duplicated onto 5B and diverged (<i>TaZIP4-B2</i>). <i>TaZIP4-B2</i> was recently shown to promote homologous pairing, synapsis and crossover, and suppress homoeologous crossover. We therefore suspected that these meiotic stabilising effects could be important for preserving wheat fertility. A CRISPR <i>Tazip4-B2</i> mutant was exploited to assess the contribution of the 5B duplicated <i>ZIP4</i> copy in maintaining pollen viability and grain setting. Analysis demonstrated abnormalities in 56% of meiocytes in the <i>Tazip4-B2</i> mutant, with micronuclei in 50% of tetrads, reduced size in 48% of pollen grains and a near 50% reduction in grain number. Further studies showed that most of the reduced grain number occurred when <i>Tazip4-B2</i> mutant plants were pollinated with the less viable <i>Tazip4-B2</i> mutant pollen rather than with wild type pollen, suggesting that the stabilising effect of <i>TaZIP4-B2</i> on meiosis has a greater consequence in subsequent male, rather than female gametogenesis. These studies reveal the extraordinary value of the wheat chromosome 5B <i>TaZIP4-B2</i> duplication to agriculture and human nutrition. Future studies should further investigate the role of <i>TaZIP4-B2</i> on female fertility and assess whether different <i>TaZIP4-B2</i> alleles exhibit variable effects on meiotic stabilisation and/or resistance to temperature change.
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