OsMTOPVIB is required for meiotic bipolar spindle assembly

Abstract

Significance The organization of microtubules into a bipolar spindle is essential for chromosome segregation. Both centrosome and chromatin-dependent spindle assembly mechanisms are well studied in animals; however, the mechanism of bipolar spindle assembly in plant meiosis remains unclear. We found the key step of plant bipolar spindle assembly is the correction of multipolar spindles into bipolar spindles at metaphase I. The multipolar spindles failed to transition into bipolar spindles in OsmtopVIB . However, the absence of cohesion subunit OsREC8 resulted in bipolar spindles in the background of OsmtopVIB . Thus, OsMTOPVIB plays a crucial role in meiotic spindle assembly. Biorientation of sister kinetochores in a univalent is essential for bipolar spindle formation when homologous recombination is absent.