title: Sequential logic of polarity determination during the haploid-to-diploid transition in Saccharomyces cerevisiae.
abstract: In many organisms, the geometry of encounter of haploid germ cells is arbitrary. In Saccharomyces cerevisiae, the resulting zygotes have been seen to bud asymmetrically in several directions as they produce diploid progeny. What mechanisms account for the choice of direction, and do the mechanisms directing polarity change over time? Distinct subgroups of cortical "landmark" proteins guide budding by haploid versus diploid cells, both of which require the Bud1/Rsr1 GTPase to link landmarks to actin. We observed that as mating pairs of haploid cells form zygotes, bud site specification progresses through three phases. The first phase follows disassembly and limited scattering of proteins that concentrated at the zone of cell contact, followed by their reassembly to produce a large medial bud. Bud1 is not required for medial placement of the initial bud. The second phase produces a contiguous bud(s) and depends on axial landmarks. As the titer of the Axl1 landmark diminishes, the third phase ultimately redirects budding toward terminal sites and is promoted by bipolar landmarks. Thus, following the initial random encounter that specifies medial budding, sequential spatial choices are orchestrated by the titer of a single cortical determinant that determines whether successive buds will be contiguous to their predecessors.
authors.affiliation: Pathology Department and Cell Biology Program, Case Western Reserve University, Cleveland, Ohio, USA Medical Scientist Training Program, School of Medicine, Case Western Reserve University, Cleveland, Ohio, USA.
authors.forename: Serendipity
authors.initials: S
authors.lastname: Zapanta Rinonos
authors.affiliation: Pathology Department and Cell Biology Program, Case Western Reserve University, Cleveland, Ohio, USA.
authors.forename: Urvashi
authors.initials: U
authors.lastname: Rai
authors.affiliation: Pathology Department and Cell Biology Program, Case Western Reserve University, Cleveland, Ohio, USA.
authors.forename: Sydney
authors.initials: S
authors.lastname: Vereb
authors.affiliation: Pathology Department and Cell Biology Program, Case Western Reserve University, Cleveland, Ohio, USA.
authors.forename: Kyle
authors.initials: K
authors.lastname: Wolf
authors.affiliation: Pathology Department and Cell Biology Program, Case Western Reserve University, Cleveland, Ohio, USA.
authors.forename: Eric
authors.initials: E
authors.lastname: Yuen
authors.affiliation: St. John's University, New York City, New York, USA.
authors.forename: Cindy
authors.initials: C
authors.lastname: Lin
authors.affiliation: Pathology Department and Cell Biology Program, Case Western Reserve University, Cleveland, Ohio, USA amt10@case.edu.
authors.forename: Alan Michael
authors.initials: AM
authors.lastname: Tartakoff
mesh_terms: D000199:Actins / Q000378:metabolism; D002455:Cell Division / Q000235:genetics*; D016764:Cell Polarity / Q000235:genetics*; D050756:Cyclin-Dependent Kinase Inhibitor Proteins / Q000378:metabolism; D004171:Diploidy; D005854:Germ Cells / Q000166:cytology*; D006238:Haploidy; D008565:Membrane Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000378:metabolism
chemical_list: D000199:Actins; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; C081353:FAR1 protein, S cerevisiae; D008565:Membrane Proteins; C483715:RAX1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C084013:RSR1 protein, S cerevisiae; D020691:rab GTP-Binding Proteins