Sporulation in budding yeast S. cerevisiae and the story of yeast aquaporin Aqy1

1. Sporulation in budding yeast S. cerevisiae and the story of yeast aquaporin Aqy1 Cecilia Geijer Göteborg University

2. Life cycle of budding yeast S. cerevisiae

3. Sporulation in S. cerevisiae • Sporulation is initiated in diploid yeast cells starved for nitrogen and glucose (or other fermentable carbon source). • Spores can resist harsh treatments such as drought, frost, heat and chemical exposure. • Under favorable conditions spores germinate and release vegetative cells.

4. Sporulation in S. cerevisiae – the process • Sporulation encompasses two overlapping processes: meiosis and spore formation. • Cells go through meiosis which leads to the synthesis of four haploid daughter cells; the yeast gametes. • Plasma membranes for four daugther cells are constructed within the mother cell cytoplasm, and these surrounds the four haploid nuclei. • Spore wall synthesis is initiated.

5. New data on Sporulation in yeast • Carbon limitation during the sporulation process reduces the number of spores formed per cell. Rather one good than four bad... J Cell Biol. 2005 Nov 21;171(4):627-40. Spore number control and breeding in Saccharomyces cerevisiae : a key role for a self-organizing system Christof Taxis, Philipp Keller, Zaharoula Kavagiou, Lars Juhl Jensen, Julien Colombelli, Peer Bork, Ernst H.K. Stelzer, and Michael Knop • Yeast sporulation efficiency is a quantitative trait. Nature Genetics37, 1333 - 1340 (2005) Quantitative trait loci mapped to single-nucleotide resolution in yeast Adam M Deutschbauer & Ronald W Davis

6. Aquaporins • Aquaporins mediate the transport of water across biological membranes. Some also transport other substrates such as glycerol, urea and nitrogen. • The genome of S cerevisiae contains four aquaporin genes.

7. Aqy1 is involved in sporulation Northern Blot analysis of AQY1 in strainSK1. Low basal level of expression of AQY1 in vegetative cells. Upregulation of expression ~6 h after transfer to sporulation medium (1% KAc) (The Saccharomyces cerevisiae aquaporin Aqy1 is involved in sporulation, Sidoux-Walter et al, PNAS 2004)

8. Expression of AQY1 in haploid cells AQY1 is also expressed in haploid cells experiencing nitrogen and glucose stress, but is depayed in diploid cells until spores are formed YPA OD1 KAc 1h KAc 4h KAc 8h 1n 2n 1n 2n 1n 2n 1n 2n AQY1 18S

9. Aqy1 deletion phenotypes Aquaporins in Saccharomyces: Characterization of a second functional water channel protein Jennifer M. Carbrey,* Mélanie Bonhivers,† Jef D. Boeke,‡ and Peter Agre • Haploid cells lacking aquaporins show invasive growth and cell aggregation on plate

10. Future experiments • Further analysis of AQY1 expression pattern using Northern Blots. • Try to identify transcription factors that are important for the expression of AQY1. • Find out how Aqy1 influences the surface properties of cells. How are spores effected by the presence / absence of Aqy1? • Examine the physiological function of Aqy1 in sporulating cells. Why is the aquaporin there?

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