Saccharomyces cerevisiae Budding Yeast Movie 4-5 um minutes Mitochondria Bud site EM view Nucleolus Vacuole ER/ Golgi Nucleus Nuclear envelope And Nuclear Pores Wall ~5 um The Yeast Nuclear Genome bp 16 Chromosomes (200-1600 Kbp) 12,052 Kbp nuclear genome (3.5x E. coli) roughly 6000 protein-encoding genes (the mitochondrial genome is about 76,000bp and encodes about 50 ORFs) Transcriptome Profiling Human Disease Homologs Yeast Gene TBLASTN P-value MSH2 3.8e-255 YCF1 2.4e-157 GEF1 3.4e-95 TEL1 8.8e-84 YNL161W 8.5e-82 SOD1 8.9e-56 SGS1 3.1e-50 IRA2 1.0e-28 Percent Percent Identity Similarity 43 31 33 49 41 55 24 21 65 57 58 36 65 69 34 45 Human Gene ID Mutator gene (MSH2, colon cancer) Cystic fibrosis conductance regulator (CFTR) Voltage-gated chloride ion channel Ataxia telangiectasia gene Myotonic dystrophy associated protein kinase Superoxide dismutase (SOD-1) Werner's Syndrome gene Neurofibromin (NF1) The Domestication of Yeast The Yeast Life Cycle “sex and the single yeast” Diploid (2n) Haploid (n) Alternation of Generations Mating (Conjugation) heterothallic in the mother cell mother cell The Mitotic Cell Cycle Master Regulatory Molecules Control the Cycle Transcription factors Cyclins (9 total) + CDK (Cdc28) 90 minute generation time Ori Licensing Controlling S Start Bud Site Selection by Cdc42 A Cdc42ts Mutant is Defective in Budding and Division Superposition of Spc42::GFP to mark MTOCs and Septin:GFP to mark bud site Septin::GFP Septins Ring the Bud Site Cortical Patches Target Exocytosis Contractile Ring at Cytokinesis Long Cables Support Transport Microfilaments Target the Bud The Secretory Pathway Delivers Localized Wall Synthesis Controls Growth QuickTime™ and a Cinepak Codec by Radius decompressor are needed to see this picture. Buds Movie An Intra-Nuclear Spindle Spc42::GFP DNA The Spindle Pole Body The Fungal MTOC The Cytoskeleton in Mitosis QuickTime™ and a Cinepak Codec by Radius decompressor are needed to see this picture. Tubulin::GFP QuickTime™ and a None decompressor are needed to see this picture. Myosin1(MyosinII)::GFP homotypic mutants can’t switch Mothers Switch in G1 A A HO Alpha A HO A HO Alpha Alpha Mating Type Switching After Cytokinesis A alpha a a Silent HML Active MAT Silent HMR alpha alpha a alpha a a Silenced Switching is a Gene Conversion Event Recombination Enhancer Determines the Polarity of the Switch Silenced Switching Switching at MAT Changes the Mating Type of the Cell Certain mRNAs and proteins are Transported into the Bud QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Myosin V Ash1 protein HO endonuclease Ash1 mRNA encodes a transcriptional repressor of HO expression, suppressing switching in the daughter cell QuickTime™ and a Graphics decompressor are needed to see this picture. Mating also involves polarized growth Movie Cdc42 CDC42 G-protein FUS proteins Pheromone response MAPKKKK MAPKKK MAPKK MAPK Ste5 is a scaffolding protein responsible for organizing a MAP kinase cascade Candida albicans Hyphal Growth (Invasive) A Few Questions for Thought • Describe the life cycle of Saccharomyces cerevisiae, noting relationships between mitotic growth, the alternation of generations, meiosis, conjugation and spore formation. •Review the compartments and cytoskeleton of the eukaryotic cell, comparing and contrasting what you learned in the first semester with this model yeast. •Compare and contrast (in a simple way) mammalian and fungal cell cycles. •Describe the role(s) of septins, spindle pole bodies, and CDC42 protein in the growth of E. coli. •How is a cell’s mating type identity determined? How can it switch (and why)? How is switching repressed in certain cells? Why is this important? •(After lab) Explain how a cell senses the presence of a mating partner, and what happens once it shows interest?