Development and differentiation of a ‘unicellular’ yeast
Prof. John Armstrong University of Sussex Seminar sponsored by FERMENTAS
The fission yeast Schizosaccharomyces pombe has long been popular a model single-celled eukaryote, very different from the budding yeast Saccharomyces cerevisiae and arguably closer to higher eukaryotic cells. This has been particularly the case with the study of control of the cell cycle, where much has been learned about this organism’s ordered processes of polarised linear growth. With a genome sequence and genomic tools, many more areas of its biology are now becoming amenable to study. We made the surprising discovery that, despite decades of research in many laboratories, S. pombe is not strictly unicellular. Under particular conditions of nutrient deprivation, it can form multicellular mycelia which invade deep into the growth medium, and form quite elaborate structures involving elongated cells and branched growth (1). We have identified one of the signalling pathways, involving cyclic AMP, which is required for sensing nutrient status. More recently we found that mycelia can also form in the absence of nutrient deprivation, where cell density seems to be an important trigger. We used a new library of S. pombe deletion mutants to identify genes required for this response. This has not only provided a list of genes, but helped us recognise the distinct stages by which cells recognise the conditions, attach to the growth surface and re-order their growth, and will allow a molecular dissection of each of these stages in this process of eukaryotic development. Key references: Amoah-Buahin, E., Bone N. and Armstrong, J. (2005) Hyphal growth in Schizosaccharomcyes pombe. Euk. Cell 4, 1287-1297.
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