Abstract
Gametogenesis in diploid cells of the budding yeast Saccharomyces cerevisiae produces four haploid meiotic products called spores. Spores are dormant until nutrients trigger germination, when they bud asexually or mate to return to the diploid state. Each sporulating diploid produces a mix of spores of two haploid mating types, a and α. In asexually dividing haploids, the mating types result from distinct, mutually exclusive gene expression programs responsible for production of mating pheromones and the receptors to sense them, all of which are silent in diploids. It was assumed that spores only transcribe haploid- and mating-type-specific genes upon germination. We find that dormant spores of each mating type harbor transcripts representing all these genes, with the exception of Mata1, which we found to be enriched in a spores. Mata1 transcripts, from a rare yeast gene with two introns, were mostly unspliced. If the retained introns reflect tethering to the MATa locus, this could provide a mechanism for biased inheritance. Translation of pheromones and receptors were repressed at least until germination. We find antisense transcripts to many mating genes that may be responsible. These findings add to the growing number of examples of post-transcriptional regulation of gene expression during gametogenesis.
Highlights
Several “spore-autonomous” genes, including GPD1 and YKL050C, have been previously exploited to create fluorescent markers that allow fluorescence-activated cell sorting (FACS) of spores carrying a specific allele at a given locus [20,21]
Moters is known to occur in other contexts [34]. When it comes to meiosis/sporulation in S. cerevisiae, post‐transcriptional control of
When it comes to meiosis/sporulation in S. cerevisiae, post-transcriptional control of gene expression appears to be the rule rather than the exception
Summary
The establishment of mating type in the budding yeast Saccharomyces cerevisiae was one of the first genetic circuits controlling cell fate to be understood in mechanistic detail. A and α, differ genetically by only a few thousand basepairs of DNA at a single locus (MAT), representing two alternative alleles that encode either the Mata and Mata or the Matα and Matα proteins. Mata and Matα are homeodomain proteins that together form a heterodimeric transcriptional repressor of a small number of genes (~20) important for mating by haploid cells of both mating types [5], including MATα1. Matα binds to the constitutively expressed protein Mcm to form a heterotetramer that represses a smaller number of genes (seven) mostly important for mating by a cells [5].
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