PROTEIN PHOSHATASE 2A B 'alpha and beta Maintain Centromerie Sister Chromatid Cohesion during Meiosis in Arabidopsis

The correct separation of homologous chromosomes during meiosis I, and sister chromatids during meiosis II, relies on the tight control of the cohesion complex. The phosphorylation and subsequent cleavage of the meiotic recombination protein REC8 (REC8-like family protein [SYN1] in Arabidopsis [Arabidopsis thaliana]), the alpha-kleisin subunit of the cohesion ring, along the chromosome arms at meiosis I allows crossovers and separation of homologous chromosomes without chromatid dissociation. REC8 continues to localize and function at the centromeres up to metaphase II and, in yeast and vertebrates, is protected from cleavage by means of protein phosphatase 2A (PP2A)-mediated dephosphorylation. Here, we show that, in plants, centromeric sister chromatid cohesion until meiosis II also requires the activity of a PP2A-type phosphatase complex. The combined absence of the regulatory subunits PP2AB'alpha and PP2AB'beta leads to the premature loss of chromosome cohesion in meiosis I. Male meiocytes of the pp2ab'alpha beta double mutant display premature depletion of SYN1. The PP2AA1 structural and B'alpha regulatory subunit localize specifically to centromeres until metaphase II, supporting a role for the PP2A complex in the SYN1-mediated maintenance of centromeric cohesion in plant meiosis.