Figure 4.

Distal Chromosomal DNA Is Replicated Prior to the Interstitial/Proximal Regions during Premeiotic S-Phase, Leading to a Meiotic Lag That Is Attenuated at 30°C.

The duration of premeiotic S-phase is determined by applying a pulse of BrdU (data not shown) followed by a second pulse of EdU (red) at various time intervals (A). At 22°C, nuclei no longer incorporate the EdU (red) by 13 h as they have completed S-phase, whereas at 30°C, this occurs by 9 h (A). Axis formation marked by ASY1 (green) loading has a strong bias toward the distal regions at 22°C, whereas at 30°C, this appears more even (B). Chromosome synapsis determined by ZYP1 loading (green) is first observed in the distal regions at 22°C, whereas at 30°C, it is throughout the nucleus (C). Nuclei in (A) and (C) are stained with DAPI. Bars = 10 µM.