Previous studies had shown that the brewer's yeast regulates meiosis and mating independently. The genes relevant to each process are transcribed and expressed when their specific process is underway. What the researchers discovered in C. lusitaniae, however, is that the yeast expressed genes associated with meiosis and mating during both processes. Their mating and meiosis programs were essentially fused.
"What was surprising was that when we started doing the transcriptional profiling experiments to see how genes are expressed, we weren't seeing this delineation of two programs," Bennett said. "We were seeing genes that that should have been expressed in mating only were also being expressed in meiosis and genes that should have been expressed in meiosis only were expressed in mating. In none of the other closely related species that have been characterized has something like that been seen."
The researchers showed this not only by tracking gene expression but also by knocking out genes in C. lusitaniae that in brewer's yeast are associated with just meiosis (such as IME2) or just mating (such as STE12). Knocking out either gene scuttled both processes in C. lusitaniae. Restoring the knocked out genes restored the processes.
It appeared as if sometime during its own evolution, C. lusitaniae had completely rewired its reproductive program compared to its "cousin" brewer's yeast. If that were without precedent, perhaps it could just be written off as an oddity, but there is another haploid yeast that has also evolved such a fused program: Schizosaccharo
|Contact: David Orenstein|