Fig. 7.

Cartoon of the events during the mitotic-like division in the wheat–rye amphihaploids. During the S phase, Rec8 cohesin becomes loaded onto the chromosomes, thereby joining sister chromatids. In the late prophase (end of pachytene, early diplotene), cyclin CYCA1;2 associates with CDK1; a kinetochore is formed. Metaphase I, CYCA1;2–CDKA complex activity peaks; equatorial positioning of chromosomes, sister chromatids are kept together by cohesion, and kinetochores assume back-to-back geometry and are attached to the opposite poles of the spindle. APC/C^cdc20 becomes activated to degrade securin; separase activates and cleaves cohesin rings. Cohesin is removed from both the chromosome arms and the centromeres. Consequently, SGO1–PP2A complex functions abnormally during the meiotic program. Univalents split to form sister chromatids that segregate to the poles. Anaphase I, activity of APC/C is so high that it completely degrades cyclin, and CDK1 kinase activity decreases. Division exits from meiosis