Modulation of the transcription regulatory program in yeast cells committed to sporulation
1 Departments of Molecular Genetics and Physics of Complex System, Weizmann Institute of Science, Rehovot 76100, Israel
2 Department of Genetics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
Genome Biology 2006, 7:R20 doi:10.1186/gb-2006-7-3-r20Published: 8 March 2006
Meiosis in budding yeast is coupled to the process of sporulation, where the four haploid nuclei are packaged into a gamete. This differentiation process is characterized by a point of transition, termed commitment, when it becomes independent of the environment. Not much is known about the mechanisms underlying commitment, but it is often assumed that positive feedback loops stabilize the underlying gene-expression cascade.
We describe the gene-expression program of committed cells. Sporulating cells were transferred back to growth medium at different stages of the process, and their transcription response was characterized. Most sporulation-induced genes were immediately downregulated upon transfer, even in committed cells that continued to sporulate. Focusing on the metabolic-related transcription response, we observed that pre-committed cells, as well as mature spores, responded to the transfer to growth medium in essentially the same way that vegetative cells responded to glucose. In contrast, committed cells elicited a dramatically different response.
Our results suggest that cells ensure commitment to sporulation not by stabilizing the process, but by modulating their gene-expression program in an active manner. This unique transcriptional program may optimize sporulation in an environment-specific manner.