Usually non-stressed yeast reproduce asexually via budding...
...however, stressful conditions (eg nutrient/nitrogen depletion) lead otherwise normal diploid yeast cells to generate haploid cells via sporulation, and the haploid spores then sexually reproduce/mate (conjugate), reforming new versions of diploid yeast cells.
I have not tried this, but if you have proper materials, here is a method for inducing Sporulation of Budding Yeast:
Starvation of diploid yeast cells for nitrogen and carbon sources induces meiosis and spore formation. The sporulation process can be induced in cells growing either on solid or in liquid medium.
1. Sporulation in liquid media:
2. Grow the diploid to be sporulated to an OD600 of 2.5 to 3.0 in YPD medium.
3. Transfer 1 ml culture to a sterile, disposable 15-ml tube and centrifuge 5min at 1200xg (3000rpm).
4. Pour off supernatant and resuspend cells in 5ml sterile water. Vortex to resuspend cells and repeat spin.
5. Pour off supernatant and resuspend cells in 1ml liquid sporulation medium supplemented with nutritional requirements of the particular diploid.
6. Shake at 30C for 3-6 days.
7. Look for sporulation microscopically.
10 g/l potassium acetate
1 g/l yeast extract
0.5 g/l dextrose
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