Fig. 4.

Proposed model for OsMTOPVIB function during bipolar spindle assembly. In wild type, chiasmata together with co-orientation of sister kinetochores, enables the bipolar attachment between kinetochores and microtubules. In haploid, pair2, crc1, and Osspo11-1, the mono-orientation of sister kinetochores of some univalents is converted into a biorientation, leading to the generation of tensions and construction of bipolar spindles. However, in OsmtopVIB, only mono-orientation of sister kinetochores leads to multipolar spindles. After elimination of the cohesion subunit OsREC8 in the OsmtopVIB background, both biorientation and bipolar spindles appear.