Dynamics and control of sister kinetochore behavior during the meiotic divisions in Drosophila spermatocytes
Fig 7
Bi-orientation of univalents and Fzy/Cdc20-dependent separation of their sister KTs during M I.
For an analysis of the behavior of sister KTs associated with univalents during M I, time lapse imaging was performed with mnm (A,B) and tef (C,D) mutant spermatocytes expressing Cid-EGFP and His2Av-mRFP. (A) Univalents were assigned to three classes according to position and shape of the associated Cid-EGFP signals during exit from M I (left panel). Class I univalents have sister KTs within the metaphase plate and stretched apart, indicating bi-orientation. In class II univalents, sister KTs are also within the metaphase plate but unresolved, and class III univalents have unresolved sister KTs close to a spindle pole. High magnification views (right panel) display the Cid-EGFP signals of the indicated univalents (I, II, III) at different time points (t1, t2, t3; see also B). Scale bar = 3 μm (left panel) and 0.5 μm (right panel). (B) Distance between the two sister KTs of the indicated univalents plotted over time. The dotted lines mark the indicated division phase transitions. The arrows (t1, t2, t3) mark the time points displayed in panel A on the right. (C) Still frames from different time points (see also D). The KTs of the XY bivalent (white arrows) and of representative univalents (colored arrowheads) are marked. Scale bar = 2μm. (D) Distance between the two sister KTs of the univalents indicated in (C) plotted over time (y axis on the left), as well as separation of the KTs on the X and Y chromosome (DKT XY) (y axis on the right). The rapid increase in DKT XY reveals anaphase onset. The arrows (t1-t4) mark the time points displayed in (C). (E) The overall duration of M I was determined in spermatocytes with the indicated genotypes. Averages (+/- s.d.) are indicated in red. n > 10 cells from at least 3 different testes.