The Role of the Meiotic Chromosome Axis in Determining CO Outcomes in Arabidopsis

During prophase I of meiosis a proteinaceous chromosome axis forms that is required to promote inter-homolog recombination, as well as ensure that DNA is repaired off the sister chromatids. In Arabidopsis, the underlying chromosome axis scaffold comprises of the cohesins, a group of proteins that form a cohesion complex that essentially hold the chromosomes together, as well as allowing for chromosome expansion and condensation. These are the structural maintenance of chromosomes (SMC1 and SMC3), SCC1, SCC3 and the alpha Kleisin REC8 homolog, SYN1/DIF1. Superimposed onto this scaffold are the meiosis specific chromosome axis components Asynaptic 1 (ASY1) and Asynaptic3 (ASY3). It is generally considered that the cohesins and meiosis axis components act antagonistically to promote inter-homolog recombination and inter-sister recombination, respectively. In the absence of the cohesion complexes, the meiotic axes do not form whereas in the absence of ASY1 and ASY3 the cohesion complexes are still present. In Arabidopsis, multiple roles of the meiotic chromosome axis have recently been identified including chromosome pairing, synapsis, interference and prevention of multivalent formation. Understanding the regulation and function of ASY1 and ASY3 will underpin efforts to elucidate crossover number and distribution in plants.  In this talk I will present current results relating to the function of ASY1 and ASY3.