Sporulation of the budding yeast Saccharomyces cerevisiae - equivalent to gametogenesis in higher organisms, is a complex differentiation program induced by starvation of cells for nitrogen and carbon. Such environmental conditions activate coordinated, sequential changes in gene expression leading to production of haploid, stress-resistant spores. Sporulation comprises two rounds of meiosis coupled with spore morphogenesis and is tightly controlled to ensure viable progeny. This review concerns the regulation of differentiation process by nutritional and transcriptional signals.
Saccharomyces cerevisiae homologues of phosphotyrosyl phosphatase activator(PTPA) are encoded by RRD1 and RRD2, genes whose combined deletion is synthetic lethal. Previously we have shown that the lethality of rrd1,2Δ can be suppressed by increasing the osmolarity of the medium. Here we show that the lethality of rrd1,2Δ is also suppressed under oxygen-limited conditions. The absence of respiration per se is not responsible for the suppression since elimination of the mitochondrial genome or a block in heme biosynthesis fail to rescue the rrd1,2Δ double mutation.
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