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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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Loss of the cytokinesis protein Fic1 causes defects in S.pombe growth polarity.(A) Live-cell images of calcofluor-stained wild-type and fic1Δ cells. Birth scars remain unstained and appear as dark bands across cells. Arrowheads indicate monopolar cells, i.e. cells that have only grown at one end, with birth scars abutting cell ends. (B) Quantification of (A), with three trials per genotype and n>300 for each trial. Data are presented as mean ± SEM for each category. (C) Quantification of septated cells in (A) and (B), with three trials per genotype and n>200 for each trial. Data are presented as mean ± SEM for each category. (D) Live-cell GFP images of crn1-GFP and fic1Δ crn1-GFP cells. (E) Quantification of (D), with three trials per genotype and n>200 for each trial. Data are presented as mean ± SEM for each category. (F) Live-cell GFP (in green) and RFP (in magenta) merged images of rgf1-GFP sid4-RFP and fic1Δ rgf1-GFP sid4-RFP cells. (G) Quantification of (F), with three trials per genotype and n>200 for each trial. Data are presented as mean ± SEM for each category (Bars = 5 µm).
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pgen-1003004-g001: Loss of the cytokinesis protein Fic1 causes defects in S.pombe growth polarity.(A) Live-cell images of calcofluor-stained wild-type and fic1Δ cells. Birth scars remain unstained and appear as dark bands across cells. Arrowheads indicate monopolar cells, i.e. cells that have only grown at one end, with birth scars abutting cell ends. (B) Quantification of (A), with three trials per genotype and n>300 for each trial. Data are presented as mean ± SEM for each category. (C) Quantification of septated cells in (A) and (B), with three trials per genotype and n>200 for each trial. Data are presented as mean ± SEM for each category. (D) Live-cell GFP images of crn1-GFP and fic1Δ crn1-GFP cells. (E) Quantification of (D), with three trials per genotype and n>200 for each trial. Data are presented as mean ± SEM for each category. (F) Live-cell GFP (in green) and RFP (in magenta) merged images of rgf1-GFP sid4-RFP and fic1Δ rgf1-GFP sid4-RFP cells. (G) Quantification of (F), with three trials per genotype and n>200 for each trial. Data are presented as mean ± SEM for each category (Bars = 5 µm).

Mentions: Recently, our laboratory identified Fic1, which was implicated in cytokinesis based on its protein and genetic interactions and its localization to the CR [28]. In addition to defects in cytokinesis, deletion of S. pombe fic1+, which is a non-essential gene, resulted in an abnormally high percentage of cells that grew only from one end (i.e., monopolar cells) (Figure 1A–1C). Tip growth was judged using calcofluor staining, as birth scars formed at previous division sites do not stain well with calcofluor and growth can be assessed using the position of these scars relative to cell tips (Figure S1A) [5]. The growth defects observed upon fic1+ disruption suggested that Fic1 not only participates in cytokinesis but also in the establishment of bipolar cell growth.


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

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

Loss of the cytokinesis protein Fic1 causes defects in S.pombe growth polarity.(A) Live-cell images of calcofluor-stained wild-type and fic1Δ cells. Birth scars remain unstained and appear as dark bands across cells. Arrowheads indicate monopolar cells, i.e. cells that have only grown at one end, with birth scars abutting cell ends. (B) Quantification of (A), with three trials per genotype and n>300 for each trial. Data are presented as mean ± SEM for each category. (C) Quantification of septated cells in (A) and (B), with three trials per genotype and n>200 for each trial. Data are presented as mean ± SEM for each category. (D) Live-cell GFP images of crn1-GFP and fic1Δ crn1-GFP cells. (E) Quantification of (D), with three trials per genotype and n>200 for each trial. Data are presented as mean ± SEM for each category. (F) Live-cell GFP (in green) and RFP (in magenta) merged images of rgf1-GFP sid4-RFP and fic1Δ rgf1-GFP sid4-RFP cells. (G) Quantification of (F), with three trials per genotype and n>200 for each trial. Data are presented as mean ± SEM for each category (Bars = 5 µm).
© Copyright Policy
Related In: Results  -  Collection

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

pgen-1003004-g001: Loss of the cytokinesis protein Fic1 causes defects in S.pombe growth polarity.(A) Live-cell images of calcofluor-stained wild-type and fic1Δ cells. Birth scars remain unstained and appear as dark bands across cells. Arrowheads indicate monopolar cells, i.e. cells that have only grown at one end, with birth scars abutting cell ends. (B) Quantification of (A), with three trials per genotype and n>300 for each trial. Data are presented as mean ± SEM for each category. (C) Quantification of septated cells in (A) and (B), with three trials per genotype and n>200 for each trial. Data are presented as mean ± SEM for each category. (D) Live-cell GFP images of crn1-GFP and fic1Δ crn1-GFP cells. (E) Quantification of (D), with three trials per genotype and n>200 for each trial. Data are presented as mean ± SEM for each category. (F) Live-cell GFP (in green) and RFP (in magenta) merged images of rgf1-GFP sid4-RFP and fic1Δ rgf1-GFP sid4-RFP cells. (G) Quantification of (F), with three trials per genotype and n>200 for each trial. Data are presented as mean ± SEM for each category (Bars = 5 µm).
Mentions: Recently, our laboratory identified Fic1, which was implicated in cytokinesis based on its protein and genetic interactions and its localization to the CR [28]. In addition to defects in cytokinesis, deletion of S. pombe fic1+, which is a non-essential gene, resulted in an abnormally high percentage of cells that grew only from one end (i.e., monopolar cells) (Figure 1A–1C). Tip growth was judged using calcofluor staining, as birth scars formed at previous division sites do not stain well with calcofluor and growth can be assessed using the position of these scars relative to cell tips (Figure S1A) [5]. The growth defects observed upon fic1+ disruption suggested that Fic1 not only participates in cytokinesis but also in the establishment of bipolar cell growth.

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