Affinity proteomics targeting the meiotic chromosome axis protein, ASY1, from Brassica oleracea.

Meiosis is a highly complex process that underpins recombination in sexually reproducing organisms. Recent genomics studies suggest that up to several thousand genes/proteins contribute to the meiotic pathway, yet relatively few have been functionally characterised. Our understanding of the physical interactions between meiotic proteins and how the meiotic machinery interacts with other components of the cell is also limited. In this study, we used affinity proteomics targeting the meiotic chromosome axis protein, ASY1, to enrich for axis-associated proteins in Brassica oleracea anthers or meiocytes in prophase I of meiosis. LC-MS/MS analysis identified 540 proteins which co-immunoprecipitated with ASY1 in a sample-specific manner. These correspond to 485 Arabidopsis orthologues, 90% of which form a coherent predicted protein-protein interaction network which includes known and novel meiotic proteins, based on mutant analysis, but also proteins more usually associated with other cellular processes including replication and proteolysis. Our data provided new insights into the role of the chromosome axis in plant meiosis. We identified a novel axis-associated protein and showed that during prophase I, ASY1 and its interacting partner, ASY3, are extensively phosphorylated. Further studies targeting other meiotic proteins may ultimately enable the construction of a comprehensive meiosis protein-protein interaction network for higher plants.