Extended Data Fig. 2: Induction of the meiotic inducer Mei3 occurs first from the genome of the cell expressing the homeodomain protein Pi.

a, b, Mei3–sfGFP signal increases more rapidly after fusion when expressed in the cell expressing Pi. The left panels show individual traces that quantify the fluorescent signal from zygotes of heterothallic wild-type (a) or Pi–Mi-swapped (b) cells in which only one partner has mei3 tagged with sfGFP, as indicated (see Fig. 2c, g for average curves). Curves were aligned to fusion time defined by the entry into the M cell of cytosolic mCherry (expressed in the P cell). Box-and-whiskers plots in the bottom panels (see Methods) analyse data shown in the top panels, with Kruskal–Wallis P value displayed. Right panels show an example time-lapse of the cells used in the quantification. c, Biological replicates of chromatin immunoprecipitation of Pi and Mi reported in Fig. 2f. d–e, Time-lapse showing mating cells with swapped Pi and Mi coding sequences. In both cases, the P cell expresses cytosolic mCherry under control of p^map3 promoter. d, Heterothallic pak2Δ strains, n = 14. e, Mating of otherwise wild-type M cells with fus1Δ P cells, n = 5. Transient fusion, visualized by florescence exchange, leads to haploid meiosis in the M₁ partner (arrowheads indicate spores). The P cell proceeds to mate (e) or attempts to mate (d) with the M₂ cell. f, g, Quantification of mating and sporulation efficiencies in heterothallic wild type and strains with swapped Pi and Mi coding sequences induced to mate on MSL-N agar plates for 28 h. h, Spores in asci produced by mating heterothallic wild type or strains with swapped Pi and Mi were micro-dissected and the number of spores that developed colonies were counted.

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