Related Experiment Video
Updated: Jun 18, 2026
05:39
Determination of the Mating Efficiency of Haploids in Saccharomyces cerevisiae
Published on: December 2, 2022
Singularity in polarization: rewiring yeast cells to make two buds
Audrey S Howell1, Natasha S Savage, Sam A Johnson
1Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
Cell
|November 17, 2009
Summary
Yeast cells ensure single budding through a Cdc42 feedback loop. Rewiring this loop disrupted this "singularity," leading to multiple buds, highlighting the importance of rapid competition between Cdc42 clusters for proper cell division.
Area of Science:
- Cell biology
- Molecular biology
- Biophysics
Background:
- Budding yeast cells must establish polarity at a single site for proper division.
- The Rho GTPase Cdc42 concentrates at polarization sites via a positive feedback loop, crucial for polarity establishment.
- The mechanism ensuring the formation of only one bud (singularity) is not fully understood.
Purpose of the Study:
- To investigate whether the singularity of bud site selection in yeast is intrinsically linked to the specific Cdc42 positive feedback loop.
- To determine if alternative positive feedback mechanisms can maintain or disrupt bud site singularity.
- To explore the role of competition between Cdc42 clusters in enforcing single bud formation.
Main Methods:
- Disabling the endogenous Cdc42 amplification mechanism in budding yeast.
- Synthetically rewiring yeast cells to utilize a different positive feedback loop for Cdc42 concentration.
- Observing and quantifying bud formation and Cdc42 cluster dynamics in both normal and rewired cells.
- Employing mathematical modeling to simulate cluster competition and its effect on singularity.
Main Results:
- Rewired cells exhibited a loss of singularity, occasionally forming two buds.
- Even in cells forming a single bud, initial formation of multiple Cdc42 clusters was observed, with subsequent dominance of one.
- Mathematical modeling suggested that competition between Cdc42 clusters promotes singularity over time.
- In rewired cells, competition between Cdc42 clusters was slower, sometimes failing to establish a single dominant cluster before budding.
- Slowing competition in normal cells also led to occasional two-bud formation.
Conclusions:
- The specific Cdc42 positive feedback loop is critical for enforcing bud site singularity in yeast.
- Singularity is enforced by rapid competition between emerging Cdc42 clusters.
- Alternative feedback mechanisms, if not coupled with rapid competition, can lead to a failure of singularity and multiple budding events.
Related Concept Videos
01:28Yeast Signaling
Yeasts are single-celled organisms, but unlike bacteria, they are eukaryotes (cells with a nucleus). Cell signaling in yeast is similar to signaling in other eukaryotic cells. A ligand, such as a protein or a small molecule released from a yeast cell, attaches to a receptor on the cell surface. The binding stimulates second-messenger kinases to activate or inactivate transcription factors that further regulate gene expression. Many of the yeast intracellular signaling cascades have similar...
01:22Bioreactor Controls-III
Strain improvement is a foundational strategy in industrial microbiology aimed at maximizing microbial productivity, particularly because natural isolates typically yield commercially valuable products in very low concentrations. Although optimizing the culture medium and environmental conditions can improve yields, these adjustments are inherently limited by the organism’s genetic potential. As a result, the focus shifts toward genetic modifications to enhance biosynthetic capacity. The...
01:20Binary Fission
Fission is the division of a single entity into two or more parts, which regenerate into separate entities that resemble the original. Organisms in the Archaea and Bacteria domains reproduce using binary fission, in which a parent cell splits into two parts that can each grow to the size of the original parent cell. This asexual method of reproduction produces cells that are all genetically identical.
01:57Meiosis II
Meiosis II is the second and final stage of meiosis. It relies on the haploid cells produced during meiosis I, each of which contain only 23 chromosomes—one from each homologous initial pair. Importantly, each chromosome in these cells is composed of two joined copies, and when these cells enter meiosis II, the goal is to separate such sister chromatids using the same microtubule-based network employed in other division processes. The result of meiosis II is two haploid cells, each containing...
02:08Gene Conversion
Other than maintaining genome stability via DNA repair, homologous recombination plays an important role in diversifying the genome. In fact, the recombination of sequences forms the molecular basis of genomic evolution. Random and non-random permutations of genomic sequences create a library of new amalgamated sequences. These newly formed genomes can determine the fitness and survival of cells. In bacteria, homologous and non-homologous types of recombination lead to the evolution of new...