Temporal Expression of a Master Regulator Drives Synchronous Sporulation in Budding Yeast

Abstract

Yeast cells enter and undergo gametogenesis relatively asynchronously, making it technically challenging to perform stage-specific genomic and biochemical analyses. Cell-to-cell variation in the expression of the master regulator of entry into sporulation, <i>IME1</i>, has been implicated to be the underlying cause of asynchronous sporulation. Here, we find that timing of <i>IME1</i> expression is of critical importance for inducing cells to undergo sporulation synchronously. When we force expression of <i>IME1</i> from an inducible promoter in cells incubated in sporulation medium for 2 hr, the vast majority of cells exhibit synchrony during premeiotic DNA replication and meiotic divisions. Inducing <i>IME1</i> expression too early or too late affects the synchrony of sporulation. Surprisingly, our approach for synchronous sporulation does not require growth in acetate-containing medium, but can be achieved in cells grown in rich medium until saturation. Our system requires solely <i>IME1</i>, because the expression of the <i>N</i>6-methyladenosine methyltransferase <i>IME4</i>, another key regulator of early sporulation, is controlled by <i>IME1</i> itself. The approach described here can be combined easily with other stage-specific synchronization methods, and thereby applied to study specific stages of sporulation, or the complete sporulation program.