Yeast RHO3 and RHO4 ras superfamily genes are necessary for bud growth, and their defect is suppressed by a high dose of bud formation genes CDC42 and BEM1

1992 ◽  
Vol 12 (12) ◽  
pp. 5690-5699 ◽  
Author(s):  
Y Matsui ◽  
A Toh-E
Keyword(s):  
Cell Polarity ◽  
Inhibitory Effect ◽  
High Dose ◽  
Yeast Saccharomyces Cerevisiae ◽  
Bud Formation ◽  
Stabilizing Agents ◽  
Daughter Cells ◽  
Bud Emergence ◽  
Ras Superfamily ◽  
Bud Site

RHO3 and RHO4 are members of the ras superfamily genes of the yeast Saccharomyces cerevisiae and are related functionally to each other. Experiments using a conditionally expressed allele of RHO4 revealed that depletion of both the RHO3 and RHO4 gene products resulted in lysis of cells with a small bud, which could be prevented by the presence of osmotic stabilizing agents in the medium. rho3 rho4 cells incubated in medium containing an osmotic stabilizing agent were rounded and enlarged and displayed delocalized deposition of chitin and delocalization of actin patches, indicating that these cells lost cell polarity. Nine genes whose overexpression could suppress the defect of the RHO3 function were isolated (SRO genes). Two of them were identical with CDC42 and BEM1, bud site assembly genes involved in the process of bud emergence. A high dose of CDC42 complemented the rho3 defect, whereas overexpression of RHO3 had an inhibitory effect on the growth of mutants defective in the CDC24-CDC42 pathway. These results, along with comparison of cell morphology between rho3 rho4 cells and cdc24 (or cdc42) mutant cells kept under the restrictive conditions, strongly suggest that the functions of RHO3 and RHO4 are required after initiation of bud formation to maintain cell polarity during maturation of daughter cells.

scholarly journals Yeast RHO3 and RHO4 ras superfamily genes are necessary for bud growth, and their defect is suppressed by a high dose of bud formation genes CDC42 and BEM1.

1992 ◽  
Vol 12 (12) ◽  
pp. 5690-5699 ◽  
Author(s):  
Y Matsui ◽  
A Toh-E
Keyword(s):  
Cell Polarity ◽  
Inhibitory Effect ◽  
High Dose ◽  
Yeast Saccharomyces Cerevisiae ◽  
Bud Formation ◽  
Stabilizing Agents ◽  
Daughter Cells ◽  
Bud Emergence ◽  
Ras Superfamily ◽  
Bud Site

RHO3 and RHO4 are members of the ras superfamily genes of the yeast Saccharomyces cerevisiae and are related functionally to each other. Experiments using a conditionally expressed allele of RHO4 revealed that depletion of both the RHO3 and RHO4 gene products resulted in lysis of cells with a small bud, which could be prevented by the presence of osmotic stabilizing agents in the medium. rho3 rho4 cells incubated in medium containing an osmotic stabilizing agent were rounded and enlarged and displayed delocalized deposition of chitin and delocalization of actin patches, indicating that these cells lost cell polarity. Nine genes whose overexpression could suppress the defect of the RHO3 function were isolated (SRO genes). Two of them were identical with CDC42 and BEM1, bud site assembly genes involved in the process of bud emergence. A high dose of CDC42 complemented the rho3 defect, whereas overexpression of RHO3 had an inhibitory effect on the growth of mutants defective in the CDC24-CDC42 pathway. These results, along with comparison of cell morphology between rho3 rho4 cells and cdc24 (or cdc42) mutant cells kept under the restrictive conditions, strongly suggest that the functions of RHO3 and RHO4 are required after initiation of bud formation to maintain cell polarity during maturation of daughter cells.

Cdc28-Clb mitotic kinase negatively regulates bud site assembly in the budding yeast

2001 ◽  
Vol 114 (1) ◽  
pp. 207-218 ◽  
Author(s):  
C.G. Padmashree ◽  
U. Surana
Keyword(s):  
Kinase Activity ◽  
Budding Yeast ◽  
Critical Role ◽  
The Other ◽  
Yeast Saccharomyces Cerevisiae ◽  
Bud Formation ◽  
Temporal Regulation ◽  
Mitotic Kinase ◽  
Cortical Localization ◽  
Bud Site

In the budding yeast Saccharomyces cerevisiae, a prospective mother normally commences the formation of a daughter (the bud) only in the G(1) phase of the cell division cycle. This suggests a strict temporal regulation of the processes that initiate the formation of a new bud. Using cortical localization of bud site components Spa2 and Bni1 as an indicator of bud site assembly, we show that cells assemble a bud site following inactivation of the Cdc28-Clb mitotic kinase but prior to START. Interestingly, an untimely inactivation of the mitotic kinase is sufficient to drive cells to assemble a new bud site inappropriately in G(2) or M phases. The induction of Cdc28/Clb kinase activity in G(1), on the other hand, dramatically reduces a cell's ability to construct an incipient bud site. Our findings strongly suggest that the Cdc28-Clb kinase plays a critical role in the mechanism that restricts the timing of bud formation to the G(1) phase of the cell cycle.

The shape of things to come: morphogenesis in yeast and related patterns in other systems

1995 ◽  
Vol 73 (S1) ◽  
pp. 234-242 ◽  
Author(s):  
Michelle D. Mischke ◽  
John Chant
Keyword(s):  
Cell Polarity ◽  
Site Selection ◽  
Life Cycles ◽  
Yeast Saccharomyces Cerevisiae ◽  
Cell Form ◽  
Number Of Genes ◽  
Molecular Machinery ◽  
To Come ◽  
Bud Site ◽  
Present Understanding

The elaboration of cell form has fascinated biologists for generations. A vast body of literature details the life cycles, anatomy, and developmental programs of many species. The mechanisms responsible for the observed diversity of structure involve polarization, directed growth, and spatial memory. These issues of morphogenesis are currently under study in the budding yeast Saccharomyces cerevisiae and other fungi. In yeast, a number of genes are known that specifically affect either the orientation or the assembly of a polarity axis. These include the bud-site selection genes, BUD1–BUD5, as well as the polarity establishment genes, CDC24, CDC42, CDC43, and BEM1. Members of each of these classes encode elements in signal transduction type pathways. This review examines our present understanding of the molecular machinery responsible for orienting and assembling cell polarity as best understood in S. cerevisiae, and speculates about how similar machinery might function in other fungi. Key words: morphogenesis, polarity, yeast, Saccharomyces, development.

scholarly journals Cyclical Regulation of the Exocyst and Cell Polarity Determinants for Polarized Cell Growth

2005 ◽  
Vol 16 (3) ◽  
pp. 1500-1512 ◽  
Author(s):  
Allison Zajac ◽  
Xiaoli Sun ◽  
Jian Zhang ◽  
Wei Guo
Keyword(s):  
Cell Growth ◽  
Cell Polarity ◽  
Rab Protein ◽  
Daughter Cells ◽  
Downstream Effector ◽  
Actin Cable ◽  
Exocyst Complex ◽  
Bud Emergence ◽  
Polarized Cell Growth ◽  
Surface Expansion

Polarized exocytosis is important for morphogenesis and cell growth. The exocyst is a multiprotein complex implicated in tethering secretory vesicles at specific sites of the plasma membrane for exocytosis. In the budding yeast, the exocyst is localized to sites of bud emergence or the tips of small daughter cells, where it mediates secretion and cell surface expansion. To understand how exocytosis is spatially controlled, we systematically analyzed the localization of Sec15p, a member of the exocyst complex and downstream effector of the rab protein Sec4p, in various mutants. We found that the polarized localization of Sec15p relies on functional upstream membrane traffic, activated rab protein Sec4p, and its guanine exchange factor Sec2p. The initial targeting of both Sec4p and Sec15p to the bud tip depends on polarized actin cable. However, different recycling mechanisms for rab and Sec15p may account for the different kinetics of polarization for these two proteins. We also found that Sec3p and Sec15p, though both members of the exocyst complex, rely on distinctive targeting mechanisms for their localization. The assembly of the exocyst may integrate various cellular signals to ensure that exocytosis is tightly controlled. Key regulators of cell polarity such as Cdc42p are important for the recruitment of the exocyst to the budding site. Conversely, we found that the proper localization of these cell polarity regulators themselves also requires a functional exocytosis pathway. We further report that Bem1p, a protein essential for the recruitment of signaling molecules for the establishment of cell polarity, interacts with the exocyst complex. We propose that a cyclical regulatory network contributes to the establishment and maintenance of polarized cell growth in yeast.

scholarly journals Sensing a bud in the yeast morphogenesis checkpoint: a role for Elm1

2016 ◽  
Vol 27 (11) ◽  
pp. 1764-1775 ◽  
Author(s):  
Hui Kang ◽  
Denis Tsygankov ◽  
Daniel J. Lew
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Nuclear Division ◽  
Environmental Stresses ◽  
Bud Formation ◽  
Septin Ring ◽  
Bud Emergence ◽  
Bud Neck ◽  
Morphogenesis Checkpoint ◽  
Bud Site ◽  
Mitotic Inhibitor

Bud formation by Saccharomyces cerevisiae must be coordinated with the nuclear cycle to enable successful proliferation. Many environmental stresses temporarily disrupt bud formation, and in such circumstances, the morphogenesis checkpoint halts nuclear division until bud formation can resume. Bud emergence is essential for degradation of the mitotic inhibitor, Swe1. Swe1 is localized to the septin cytoskeleton at the bud neck by the Swe1-binding protein Hsl7. Neck localization of Swe1 is required for Swe1 degradation. Although septins form a ring at the presumptive bud site before bud emergence, Hsl7 is not recruited to the septins until after bud emergence, suggesting that septins and/or Hsl7 respond to a “bud sensor.” Here we show that recruitment of Hsl7 to the septin ring depends on a combination of two septin-binding kinases: Hsl1 and Elm1. We elucidate which domains of these kinases are needed and show that artificial targeting of those domains suffices to recruit Hsl7 to septin rings even in unbudded cells. Moreover, recruitment of Elm1 is responsive to bud emergence. Our findings suggest that Elm1 plays a key role in sensing bud emergence.

scholarly journals Functions and Functional Domains of the GTPase Cdc42p

2000 ◽  
Vol 11 (1) ◽  
pp. 339-354 ◽  
Author(s):  
Keith G. Kozminski ◽  
Ann J. Chen ◽  
Avital A. Rodal ◽  
David G. Drubin
Keyword(s):  
Cell Polarity ◽  
Protein Interactions ◽  
Structural Model ◽  
Nodal Point ◽  
Yeast Saccharomyces Cerevisiae ◽  
C Terminus ◽  
Ras Superfamily ◽  
Rho Family ◽  
Polarity Regulation

Cdc42p, a Rho family GTPase of the Ras superfamily, is a key regulator of cell polarity and morphogenesis in eukaryotes. Using 37 site-directed cdc42 mutants, we explored the functions and interactions of Cdc42p in the budding yeast Saccharomyces cerevisiae. Cytological and genetic analyses of thesecdc42 mutants revealed novel and diverse phenotypes, showing that Cdc42p possesses at least two distinct essential functions and acts as a nodal point of cell polarity regulation in vivo. In addition, mapping the functional data for each cdc42mutation onto a structural model of the protein revealed as functionally important a surface of Cdc42p that is distinct from the canonical protein-interacting domains (switch I, switch II, and the C terminus) identified previously in members of the Ras superfamily. This region overlaps with a region (α5-helix) recently predicted by structural models to be a specificity determinant for Cdc42p-protein interactions.

scholarly journals O-Glycosylation of Axl2/Bud10p by Pmt4p Is Required for Its Stability, Localization, and Function in Daughter Cells

1999 ◽  
Vol 145 (6) ◽  
pp. 1177-1188 ◽  
Author(s):  
Sylvia L. Sanders ◽  
Martina Gentzsch ◽  
Widmar Tanner ◽  
Ira Herskowitz
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Site Selection ◽  
Surface Proteins ◽  
Cell Type ◽  
Yeast Saccharomyces Cerevisiae ◽  
Cell Surface Proteins ◽  
Daughter Cells ◽  
Mother Cells ◽  
And Function ◽  
Bud Site

Cells of the yeast Saccharomyces cerevisiae choose bud sites in a manner that is dependent upon cell type: a and α cells select axial sites; a/α cells utilize bipolar sites. Mutants specifically defective in axial budding were isolated from an α strain using pseudohyphal growth as an assay. We found that a and α mutants defective in the previously identified PMT4 gene exhibit unipolar, rather than axial budding: mother cells choose axial bud sites, but daughter cells do not. PMT4 encodes a protein mannosyl transferase (pmt) required for O-linked glycosylation of some secretory and cell surface proteins (Immervoll, T., M. Gentzsch, and W. Tanner. 1995. Yeast. 11:1345–1351). We demonstrate that Axl2/Bud10p, which is required for the axial budding pattern, is an O-linked glycoprotein and is incompletely glycosylated, unstable, and mislocalized in cells lacking PMT4. Overexpression of AXL2 can partially restore proper bud-site selection to pmt4 mutants. These data indicate that Axl2/Bud10p is glycosylated by Pmt4p and that O-linked glycosylation increases Axl2/ Bud10p activity in daughter cells, apparently by enhancing its stability and promoting its localization to the plasma membrane.

scholarly journals Interactions among Rax1p, Rax2p, Bud8p, and Bud9p in Marking Cortical Sites for Bipolar Bud-site Selection in Yeast

2004 ◽  
Vol 15 (11) ◽  
pp. 5145-5157 ◽  
Author(s):  
Pil Jung Kang ◽  
Elizabeth Angerman ◽  
Kenichi Nakashima ◽  
John R. Pringle ◽  
Hay-Oak Park
Keyword(s):  
Cell Cortex ◽  
Type I ◽  
Yeast Saccharomyces Cerevisiae ◽  
Daughter Cells ◽  
Division Site ◽  
Distal Pole ◽  
Mother And Daughter ◽  
Mother Cells ◽  
Diploid Cells ◽  
Bud Site

In the budding yeast Saccharomyces cerevisiae, selection of the bud site determines the axis of polarized cell growth and eventual oriented cell division. Bud sites are selected in specific patterns depending on cell type. These patterns appear to depend on distinct types of marker proteins in the cell cortex; in particular, the bipolar budding of diploid cells depends on persistent landmarks at the birth-scar-distal and -proximal poles that involve the proteins Bud8p and Bud9p, respectively. Rax1p and Rax2p also appear to function specifically in bipolar budding, and we report here a further characterization of these proteins and of their interactions with Bud8p and Bud9p. Rax1p and Rax2p both appear to be integral membrane proteins. Although commonly used programs predict different topologies for Rax2p, glycosylation studies indicate that it has a type I orientation, with its long N-terminal domain in the extracytoplasmic space. Analysis of rax1 and rax2 mutant budding patterns indicates that both proteins are involved in selecting bud sites at both the distal and proximal poles of daughter cells as well as near previously used division sites on mother cells. Consistent with this, GFP-tagged Rax1p and Rax2p were both observed at the distal pole as well as at the division site on both mother and daughter cells; localization to the division sites was persistent through multiple cell cycles. Localization of Rax1p and Rax2p was interdependent, and biochemical studies showed that these proteins could be copurified from yeast. Bud8p and Bud9p could also be copurified with Rax1p, and localization studies provided further evidence of interactions. Localization of Rax1p and Rax2p to the bud tip and distal pole depended on Bud8p, and normal localization of Bud8p was partially dependent on Rax1p and Rax2p. Although localization of Rax1p and Rax2p to the division site did not appear to depend on Bud9p, normal localization of Bud9p appeared largely or entirely dependent on Rax1p and Rax2p. Taken together, the results indicate that Rax1p and Rax2p interact closely with each other and with Bud8p and Bud9p in the establishment and/or maintenance of the cortical landmarks for bipolar budding.

scholarly journals Cell-cycle control of cell polarity in yeast

2018 ◽  
Vol 218 (1) ◽  
pp. 171-189 ◽  
Author(s):  
Kyle D. Moran ◽  
Hui Kang ◽  
Ana V. Araujo ◽  
Trevin R. Zyla ◽  
Koji Saito ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Polarity ◽  
Mammalian Cells ◽  
Feedback Loop ◽  
Cell Cycle Control ◽  
Yeast Saccharomyces Cerevisiae ◽  
Positive Feedback Loop ◽  
Cyclin Dependent Kinases ◽  
Daughter Cells ◽  
Rho Family

In many cells, morphogenetic events are coordinated with the cell cycle by cyclin-dependent kinases (CDKs). For example, many mammalian cells display extended morphologies during interphase but round up into more spherical shapes during mitosis (high CDK activity) and constrict a furrow during cytokinesis (low CDK activity). In the budding yeast Saccharomyces cerevisiae, bud formation reproducibly initiates near the G1/S transition and requires activation of CDKs at a point called “start” in G1. Previous work suggested that CDKs acted by controlling the ability of cells to polarize Cdc42, a conserved Rho-family GTPase that regulates cell polarity and the actin cytoskeleton in many systems. However, we report that yeast daughter cells can polarize Cdc42 before CDK activation at start. This polarization operates via a positive feedback loop mediated by the Cdc42 effector Ste20. We further identify a major and novel locus of CDK action downstream of Cdc42 polarization, affecting the ability of several other Cdc42 effectors to localize to the polarity site.

scholarly journals Patterns of bud-site selection in the yeast Saccharomyces cerevisiae.

1995 ◽  
Vol 129 (3) ◽  
pp. 751-765 ◽  
Author(s):  
J Chant ◽  
J R Pringle
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Time Lapse ◽  
Growth Conditions ◽  
Alpha Cells ◽  
Yeast Saccharomyces Cerevisiae ◽  
Cell Cycles ◽  
Daughter Cells ◽  
Division Site ◽  
Mother Cells ◽  
Bud Site

Cells of the yeast Saccharomyces cerevisiae select bud sites in either of two distinct spatial patterns, known as axial (expressed by a and alpha cells) and bipolar (expressed by a/alpha cells). Fluorescence, time-lapse, and scanning electron microscopy have been used to obtain more precise descriptions of these patterns. From these descriptions, we conclude that in the axial pattern, the new bud forms directly adjacent to the division site in daughter cells and directly adjacent to the immediately preceding division site (bud site) in mother cells, with little influence from earlier sites. Thus, the division site appears to be marked by a spatial signal(s) that specifies the location of the new bud site and is transient in that it only lasts from one budding event to the next. Consistent with this conclusion, starvation and refeeding of axially budding cells results in the formation of new buds at nonaxial sites. In contrast, in bipolar budding cells, both poles are specified persistently as potential bud sites, as shown by the observations that a pole remains competent for budding even after several generations of nonuse and that the poles continue to be used for budding after starvation and refeeding. It appears that the specification of the two poles as potential bud sites occurs before a daughter cell forms its first bud, as a daughter can form this bud near either pole. However, there is a bias towards use of the pole distal to the division site. The strength of this bias varies from strain to strain, is affected by growth conditions, and diminishes in successive cell cycles. The first bud that forms near the distal pole appears to form at the very tip of the cell, whereas the first bud that forms near the pole proximal to the original division site (as marked by the birth scar) is generally somewhat offset from the tip and adjacent to (or overlapping) the birth scar. Subsequent buds can form near either pole and appear almost always to be adjacent either to the birth scar or to a previous bud site. These observations suggest that the distal tip of the cell and each division site carry persistent signals that can direct the selection of a bud site in any subsequent cell cycle.

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