Mitosis and meiosis both rely on cohesin, which embraces the sister chromatids and plays a crucial role for the faithful distribution of chromosomes to daughter cells. Prior to the cleavage by Separase at anaphase onset, cohesin is largely removed from chromosomes by the non-proteolytic action of WINGS APART-LIKE (WAPL), a mechanism referred to as the prophase pathway. To prevent the premature loss of sister chromatid cohesion, WAPL is inhibited in early mitosis by Sororin. However, Sororin homologs have only been found to function as WAPL inhibitors during mitosis in vertebrates and Drosophila. Here we show that SWITCH 1/DYAD defines a WAPL antagonist that acts in meiosis of Arabidopsis. Crucially, SWI1 becomes dispensable for sister chromatid cohesion in the absence of WAPL. Despite the lack of any sequence similarities, we found that SWI1 is regulated and functions in a similar manner as Sororin hence likely representing a case of convergent molecular evolution across the eukaryotic kingdom.

有丝分裂和减数分裂都依赖于粘着蛋白，粘着蛋白包含姐妹染色单体，并且对于染色体向子代细胞的忠实分布起着至关重要的作用。在后期分离酶裂解之前，通过WINGS APART-LIKE（WAPL）的非蛋白水解作用将粘附蛋白从染色体上大量去除，该机制被称为前期途径。为防止姐妹染色单体内聚力过早丧失，Sororin抑制了有丝分裂早期的WAPL。然而，仅发现索罗林同系物在脊椎动物和果蝇的有丝分裂过程中起WAPL抑制剂的作用。在这里，我们显示SWITCH 1 / DYAD定义了一种WAPL拮抗剂，它在拟南芥的减数分裂中起作用。至关重要的是，在不存在SWI1的情况下，姐妹染色单体的内聚必不可少WAPL。尽管缺少任何序列相似性，我们发现SWI1的调控和功能与Sororin相似，因此可能代表了整个真核生物分子进化的案例。