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Cytokinesis-based constraints on polarized cell growth in fission yeast.

Bohnert KA, Gould KL - PLoS Genet. (2012)

Bottom Line: Intriguingly, such cells elongated constitutively at new ends unless cytokinesis was perturbed.We posit that such constraints facilitate invasive fungal growth, as cytokinesis mutants displaying bipolar growth defects formed numerous pseudohyphae.Collectively, these data highlight a role for previous cell cycles in defining a cell's capacity to polarize at specific sites, and they additionally provide insight into how a unicellular yeast can transition into a quasi-multicellular state.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute and Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.

ABSTRACT
The rod-shaped fission yeast Schizosaccharomyces pombe, which undergoes cycles of monopolar-to-bipolar tip growth, is an attractive organism for studying cell-cycle regulation of polarity establishment. While previous research has described factors mediating this process from interphase cell tips, we found that division site signaling also impacts the re-establishment of bipolar cell growth in the ensuing cell cycle. Complete loss or targeted disruption of the non-essential cytokinesis protein Fic1 at the division site, but not at interphase cell tips, resulted in many cells failing to grow at new ends created by cell division. This appeared due to faulty disassembly and abnormal persistence of the cell division machinery at new ends of fic1Δ cells. Moreover, additional mutants defective in the final stages of cytokinesis exhibited analogous growth polarity defects, supporting that robust completion of cell division contributes to new end-growth competency. To test this model, we genetically manipulated S. pombe cells to undergo new end take-off immediately after cell division. Intriguingly, such cells elongated constitutively at new ends unless cytokinesis was perturbed. Thus, cell division imposes constraints that partially override positive controls on growth. We posit that such constraints facilitate invasive fungal growth, as cytokinesis mutants displaying bipolar growth defects formed numerous pseudohyphae. Collectively, these data highlight a role for previous cell cycles in defining a cell's capacity to polarize at specific sites, and they additionally provide insight into how a unicellular yeast can transition into a quasi-multicellular state.

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Cytokinesis mutants with growth polarity defects exhibit enhanced invasiveness.(A) Invasive growth assays for strains of the indicated genotypes on 2% agar. Cells were spotted on rich medium and incubated for 20 days at 29°C (top panel). Colonies were then rinsed under a stream of water and rubbed off (bottom panel). (B) Quantification of pseudohyphae in (A), with n≥3 for each genotype. Data are presented as mean ± SEM for each genotype. (C) Image of fic1Δ pseudohyphae in 2% agar, with enlarged images on the right. (D) Invasive growth assays for tea1-for3 and tea1-for3 fic1Δ strains on 2% agar. Cells were spotted on rich medium and incubated for 20 days at 29°C (top panel). Colonies were then rinsed under a stream of water and rubbed off (bottom panel). (E) Quantification of pseudohyphae in (D), with n≥3 for each genotype. Data are presented as mean ± SEM for each genotype. (F) Colony growth of strains of the indicated genotypes on rich medium containing 2% (top panel) or 0.3% agar (middle panel). Cells were spotted and incubated for 12 days at 29°C. Schematics of colony growth on 0.3% agar are also given (bottom panel), with white areas representing growth on the agar surface and black areas representing growth into the agar (Bars = 5 µm).
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pgen-1003004-g009: Cytokinesis mutants with growth polarity defects exhibit enhanced invasiveness.(A) Invasive growth assays for strains of the indicated genotypes on 2% agar. Cells were spotted on rich medium and incubated for 20 days at 29°C (top panel). Colonies were then rinsed under a stream of water and rubbed off (bottom panel). (B) Quantification of pseudohyphae in (A), with n≥3 for each genotype. Data are presented as mean ± SEM for each genotype. (C) Image of fic1Δ pseudohyphae in 2% agar, with enlarged images on the right. (D) Invasive growth assays for tea1-for3 and tea1-for3 fic1Δ strains on 2% agar. Cells were spotted on rich medium and incubated for 20 days at 29°C (top panel). Colonies were then rinsed under a stream of water and rubbed off (bottom panel). (E) Quantification of pseudohyphae in (D), with n≥3 for each genotype. Data are presented as mean ± SEM for each genotype. (F) Colony growth of strains of the indicated genotypes on rich medium containing 2% (top panel) or 0.3% agar (middle panel). Cells were spotted and incubated for 12 days at 29°C. Schematics of colony growth on 0.3% agar are also given (bottom panel), with white areas representing growth on the agar surface and black areas representing growth into the agar (Bars = 5 µm).

Mentions: S. pombe undergoing a dimorphic switch from single-celled to invasive form grow primarily in a monopolar fashion at old ends [39], [40]. Moreover, it has been postulated that cytokinesis errors might contribute to a hyphal-like transition in S. pombe[41]. We therefore considered that cytokinesis-based constraints on S. pombe growth polarity might facilitate invasive growth transitions. Using techniques similar to those described previously [40], [59], we tested whether various cytokinesis mutants displaying defective bipolar growth could form pseudohyphae into 2% agar. Cells lacking Fic1 or its interacting partners Cyk3 or Imp2 were significantly more invasive than wild-type cells (Figure 9A–9B). Like other invasive S. pombe mutants [39], [40], these mutants formed pseudohyphae composed of single cells oriented in filament-like projections (Figure 9C and Figure S7A). In addition to these strains, we found other cytokinesis mutants exhibiting high degrees of monopolar growth (spn1Δ, cdc7-24, and vps24Δ) to also be highly invasive and to form pseudohyphal projections into 2% agar (Figure 9A–9B and Figure S7A). Of note, the vps24Δ strain showed drastically more invasive growth than the others, though the reasons for this are currently unclear. rlc1Δ and pxl1Δ, which possess cytokinesis defects that do not considerably impact polarized cell growth (Figure 6C–6D and Figure S5A), invaded less efficiently on 2% agar than cytokinesis mutants exhibiting NETO defects (Figure 9A–9B). This supports the notion that defective cytokinesis promotes the dimorphic switch most robustly when it results in faulty NETO. As has previously been observed, tea1Δ also invaded well on 2% agar (Figure S7B–S7D). Thus, though cytokinesis-based constraints on growth polarity support enhanced S. pombe invasiveness, other polarity defects, which are not entirely specific to new ends, can do so as well.


Cytokinesis-based constraints on polarized cell growth in fission yeast.

Bohnert KA, Gould KL - PLoS Genet. (2012)

Cytokinesis mutants with growth polarity defects exhibit enhanced invasiveness.(A) Invasive growth assays for strains of the indicated genotypes on 2% agar. Cells were spotted on rich medium and incubated for 20 days at 29°C (top panel). Colonies were then rinsed under a stream of water and rubbed off (bottom panel). (B) Quantification of pseudohyphae in (A), with n≥3 for each genotype. Data are presented as mean ± SEM for each genotype. (C) Image of fic1Δ pseudohyphae in 2% agar, with enlarged images on the right. (D) Invasive growth assays for tea1-for3 and tea1-for3 fic1Δ strains on 2% agar. Cells were spotted on rich medium and incubated for 20 days at 29°C (top panel). Colonies were then rinsed under a stream of water and rubbed off (bottom panel). (E) Quantification of pseudohyphae in (D), with n≥3 for each genotype. Data are presented as mean ± SEM for each genotype. (F) Colony growth of strains of the indicated genotypes on rich medium containing 2% (top panel) or 0.3% agar (middle panel). Cells were spotted and incubated for 12 days at 29°C. Schematics of colony growth on 0.3% agar are also given (bottom panel), with white areas representing growth on the agar surface and black areas representing growth into the agar (Bars = 5 µm).
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3475658&req=5

pgen-1003004-g009: Cytokinesis mutants with growth polarity defects exhibit enhanced invasiveness.(A) Invasive growth assays for strains of the indicated genotypes on 2% agar. Cells were spotted on rich medium and incubated for 20 days at 29°C (top panel). Colonies were then rinsed under a stream of water and rubbed off (bottom panel). (B) Quantification of pseudohyphae in (A), with n≥3 for each genotype. Data are presented as mean ± SEM for each genotype. (C) Image of fic1Δ pseudohyphae in 2% agar, with enlarged images on the right. (D) Invasive growth assays for tea1-for3 and tea1-for3 fic1Δ strains on 2% agar. Cells were spotted on rich medium and incubated for 20 days at 29°C (top panel). Colonies were then rinsed under a stream of water and rubbed off (bottom panel). (E) Quantification of pseudohyphae in (D), with n≥3 for each genotype. Data are presented as mean ± SEM for each genotype. (F) Colony growth of strains of the indicated genotypes on rich medium containing 2% (top panel) or 0.3% agar (middle panel). Cells were spotted and incubated for 12 days at 29°C. Schematics of colony growth on 0.3% agar are also given (bottom panel), with white areas representing growth on the agar surface and black areas representing growth into the agar (Bars = 5 µm).
Mentions: S. pombe undergoing a dimorphic switch from single-celled to invasive form grow primarily in a monopolar fashion at old ends [39], [40]. Moreover, it has been postulated that cytokinesis errors might contribute to a hyphal-like transition in S. pombe[41]. We therefore considered that cytokinesis-based constraints on S. pombe growth polarity might facilitate invasive growth transitions. Using techniques similar to those described previously [40], [59], we tested whether various cytokinesis mutants displaying defective bipolar growth could form pseudohyphae into 2% agar. Cells lacking Fic1 or its interacting partners Cyk3 or Imp2 were significantly more invasive than wild-type cells (Figure 9A–9B). Like other invasive S. pombe mutants [39], [40], these mutants formed pseudohyphae composed of single cells oriented in filament-like projections (Figure 9C and Figure S7A). In addition to these strains, we found other cytokinesis mutants exhibiting high degrees of monopolar growth (spn1Δ, cdc7-24, and vps24Δ) to also be highly invasive and to form pseudohyphal projections into 2% agar (Figure 9A–9B and Figure S7A). Of note, the vps24Δ strain showed drastically more invasive growth than the others, though the reasons for this are currently unclear. rlc1Δ and pxl1Δ, which possess cytokinesis defects that do not considerably impact polarized cell growth (Figure 6C–6D and Figure S5A), invaded less efficiently on 2% agar than cytokinesis mutants exhibiting NETO defects (Figure 9A–9B). This supports the notion that defective cytokinesis promotes the dimorphic switch most robustly when it results in faulty NETO. As has previously been observed, tea1Δ also invaded well on 2% agar (Figure S7B–S7D). Thus, though cytokinesis-based constraints on growth polarity support enhanced S. pombe invasiveness, other polarity defects, which are not entirely specific to new ends, can do so as well.

Bottom Line: Intriguingly, such cells elongated constitutively at new ends unless cytokinesis was perturbed.We posit that such constraints facilitate invasive fungal growth, as cytokinesis mutants displaying bipolar growth defects formed numerous pseudohyphae.Collectively, these data highlight a role for previous cell cycles in defining a cell's capacity to polarize at specific sites, and they additionally provide insight into how a unicellular yeast can transition into a quasi-multicellular state.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute and Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.

ABSTRACT
The rod-shaped fission yeast Schizosaccharomyces pombe, which undergoes cycles of monopolar-to-bipolar tip growth, is an attractive organism for studying cell-cycle regulation of polarity establishment. While previous research has described factors mediating this process from interphase cell tips, we found that division site signaling also impacts the re-establishment of bipolar cell growth in the ensuing cell cycle. Complete loss or targeted disruption of the non-essential cytokinesis protein Fic1 at the division site, but not at interphase cell tips, resulted in many cells failing to grow at new ends created by cell division. This appeared due to faulty disassembly and abnormal persistence of the cell division machinery at new ends of fic1Δ cells. Moreover, additional mutants defective in the final stages of cytokinesis exhibited analogous growth polarity defects, supporting that robust completion of cell division contributes to new end-growth competency. To test this model, we genetically manipulated S. pombe cells to undergo new end take-off immediately after cell division. Intriguingly, such cells elongated constitutively at new ends unless cytokinesis was perturbed. Thus, cell division imposes constraints that partially override positive controls on growth. We posit that such constraints facilitate invasive fungal growth, as cytokinesis mutants displaying bipolar growth defects formed numerous pseudohyphae. Collectively, these data highlight a role for previous cell cycles in defining a cell's capacity to polarize at specific sites, and they additionally provide insight into how a unicellular yeast can transition into a quasi-multicellular state.

Show MeSH
Related in: MedlinePlus