Figure 1.

Live imaging of fission yeast meiosis and measurement of bouquet stage extension. (a) Schematic diagram of meiotic progression. t0, t1, t2 and t3 indicate time of the beginning of Mei4 expression, the end of chromosome oscillation, the beginning of telomere release (the end of bouquet configuration) and SPB separation, respectively. The chromosomal bouquet is observed throughout meiotic prophase (highlighted with a blue curved bracket). This stage can be divided into the ‘horsetail stage’ (black arrow line flanked by t0 and t1) and the ‘post-horsetail stage’ (orange arrow line flanked by t1 and t3). Delayed DNA repair extends the post-horsetail stage within the bouquet stage. (b–d) Series of frames from films of live fission yeast undergoing meiosis (b: wild type, c: rdh54Δ, D: rdh54Δ rad3Δ). The SPB, Mei4, telomeres and chromosomes were visualised via endogenously tagged Sid4-mCherry, Mei4-mCherry, Taz1-YFP and Hht1-Cerulean, respectively. Merged images are presented. Individual channels are shown in Supplementary Figure S2. Cell images were captured every 5 min, and selected time frames are shown. Numbers below the slides represent minutes since Mei4 stains nuclei (t0: see details in Supplementary Figure S1C). The end of meiotic prophase (t3) is defined by SPB separation and chromosome condensation. The period between t0 and t3 is defined as the 'meiotic prophase' in this system. The post-horsetail stage is highlighted with the orange arrow lines. Scale bars equal 5 μm. (b) An example of average wild-type meiosis. Telomeres cluster at the SPB, representing bouquet formation, during meiotic prophase SPB oscillation pulls chromosomes to exhibit chromosomal ‘horsetail’ movement until 110 min (t1). The SPB settles at the centre of a cell, and separates when telomeres dissociate from the SPB and disperse (telomere fireworks, t2: 125 min). (c) rdh54Δ cells extend the post-horsetail stage (t1: 100 min). Telomere dissociation is observed at 160 min (t2) when the SPB separates (t3). The SPB segregates equally twice through meiosis; however, chromosome segregation is defective. (d) rdh54Δ rad3Δ cells exhibit shortened post-horsetail stage and telomere dissociation (t2) is observed at 130 min. (e) The duration of the events for individual cells are shown. Dot plots represent time distributions of meiotic prophase [t3–t0] (green circle), the bouquet stage [t2–t0] (magenta triangle) and the horsetail stage [t1–t0] (black anti-triangle). Up to 20 cells were filmed per day and the total examined samples are summarised. The sample number (n=) is indicated below the genotype. For values in each sample, see Supplementary Table S2.