Loss of Dhc1 or Hrs1 confers long-lived centromere–SPB contact in bqt1Δ zygotes. (A–F) All labels are as in Fig 2 with Mis6-GFP marking the centromere. Bars: (black) 5 µm; (gray) 1 µm. (A) Centromeres are absent from the SPB during horsetail movement in WT meiotic prophase. (B) Chromatin occasionally follows the SPB during prophase in bqt1Δ cells; sporadic centromere–SPB contacts (inset and magnified in yellow) confer bipolar spindle formation. (C and D) In dhc1Δ bqt1⁺ and hrs1Δ bqt1⁺ zygotes, vigorous SPB movement is abolished but centromeres are released from the SPB. (E and F) In contrast, dhc1Δ bqt1Δ and hrs1Δ bqt1Δ zygotes maintain at least one centromere at the SPB throughout prophase, ensuring normal spindle formation. (G) Although only around 60% of bqt1Δ cells show centromere–SPB contacts, all dhc1Δ bqt1Δ and the majority of hrs1Δ bqt1Δ cells show this interaction. No such contacts are observed in WT, dhc1Δ, or hrs1Δ cells. The analyses use Mis6-GFP as a centromere marker; the faintness of this marker explains the appearance of cells in which no centromere–SPB contact can be seen in a hrs1Δ bqt1Δ setting. Using the brighter Swi6-GFP as a marker for centromeres, we observe contact throughout in all cells (not depicted). (H) Quantitation shows complete restoration of bqt1Δ spindle formation by hrs1⁺ or dhc1⁺ deletion. n is the total number of cells scored from greater than six independent experiments. ****, P < 0.0001. (I) Categorization of zygotes according to longevity of their centromere–SPB contacts. The majority of dhc1Δ bqt1Δ cells show “throughout” (entire length of horsetail stage) prophase centromere–SPB contacts. All cells scored for this figure are more extensively analyzed in Fig. S1 G. The data shown are from three independent experiments analyzing >50 cells each. *, 0.01 < P < 0.05.