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The cytokinesis gene KEULE encodes a Sec1 protein that binds the syntaxin KNOLLE.

Assaad FF, Huet Y, Mayer U, Jürgens G - J. Cell Biol. (2001)

Bottom Line: KEULE is characteristic of a Sec1 protein in that it appears to exist in two forms: soluble or peripherally associated with membranes.More importantly, KEULE binds the cytokinesis-specific syntaxin KNOLLE.Sec1 proteins are key regulators of vesicle trafficking, capable of integrating a large number of intra- and/or intercellular signals.

View Article: PubMed Central - PubMed

Affiliation: Genetics and Microbiology Institute, Ludwig Maximilians University, D-80638 Munich, Germany. fassaad@andrew2.stanford.edu

ABSTRACT
KEULE is required for cytokinesis in Arabidopsis thaliana. We have positionally cloned the KEULE gene and shown that it encodes a Sec1 protein. KEULE is expressed throughout the plant, yet appears enriched in dividing tissues. Cytokinesis-defective mutant sectors were observed in all somatic tissues upon transformation of wild-type plants with a KEULE-green fluorescent protein gene fusion, suggesting that KEULE is required not only during embryogenesis, but at all stages of the plant's life cycle. KEULE is characteristic of a Sec1 protein in that it appears to exist in two forms: soluble or peripherally associated with membranes. More importantly, KEULE binds the cytokinesis-specific syntaxin KNOLLE. Sec1 proteins are key regulators of vesicle trafficking, capable of integrating a large number of intra- and/or intercellular signals. As a cytokinesis-related Sec1 protein, KEULE appears to represent a novel link between cell cycle progression and the membrane fusion apparatus.

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KEULE is required for cytokinesis in somatic cells throughout the plant life cycle. (A) keule seedling, with its characteristic bloated surface. (B) Scanning electron micrograph of a keule seedling (hypocotyl), showing the bloated cells at the surface layer. (C) Wild-type flower. D–G are epimutations at the keule locus due most likely to cosuppression in transformants harboring a P35S::GFP-KEULE gene fusion. (D) Sectors are seen on petals and sepals, but not on the carpels or stamens. (E) Sector taking over the entire apical meristem. (F) Bloated, keule-like surface cells (arrows) in somatic sector boxed in D. (G) Lines with large numbers of mutant sectors (such as E) matured as a cluster or large rosette of fertile silliques. (H) Using an anti-GFP antibody, we fail to detect the GFP-KEULE fusion protein in cytokinesis-defective sectored plants (epimutant), but do see it in nonsectored siblings (normal). Anti-protein disulfide isomerase (PDI) was used as a loading control. Bar: (A) 300 μm; (B) 45 μm; (E) 200 μm; (F) 170 μm.
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Figure 4: KEULE is required for cytokinesis in somatic cells throughout the plant life cycle. (A) keule seedling, with its characteristic bloated surface. (B) Scanning electron micrograph of a keule seedling (hypocotyl), showing the bloated cells at the surface layer. (C) Wild-type flower. D–G are epimutations at the keule locus due most likely to cosuppression in transformants harboring a P35S::GFP-KEULE gene fusion. (D) Sectors are seen on petals and sepals, but not on the carpels or stamens. (E) Sector taking over the entire apical meristem. (F) Bloated, keule-like surface cells (arrows) in somatic sector boxed in D. (G) Lines with large numbers of mutant sectors (such as E) matured as a cluster or large rosette of fertile silliques. (H) Using an anti-GFP antibody, we fail to detect the GFP-KEULE fusion protein in cytokinesis-defective sectored plants (epimutant), but do see it in nonsectored siblings (normal). Anti-protein disulfide isomerase (PDI) was used as a loading control. Bar: (A) 300 μm; (B) 45 μm; (E) 200 μm; (F) 170 μm.

Mentions: GFP fusions (NH2- and COOH-terminal) of the KEULE full length sequence under the transcriptional control of the CaMV 35S promoter (a strong, fairly constitutive promoter) were introduced into wild-type Arabidopsis plants. The gene fusions failed to rescue the mutant phenotype (see Materials and Methods) and we therefore do not present the GFP fluorescence here as this was weakly and/or erroneously expressed and has unfortunately not enabled us to localize the KEULE protein. Interestingly, cytokinesis-defective mutant sectors (such as depicted in Fig. 4 D) appeared on a small fraction (∼6–7%, or 40 affected individuals in a population of ∼600 plants) of the wild-type transformants (with the NH2-terminal fusion). These were seen on all somatic organs of the plants including petals and sepals (Fig. 4D and Fig. F) as well as the apical meristem (Fig. 4 E) but not on the carpels, siliques, or stamens (Fig. 4 D). Cellular analysis of these sectors revealed the presence of large, bloated cells (Fig. 4 F, confocal analysis not shown) characteristic of keule mutants (Fig. 4A and Fig. B). Sectored plants exhibited striking clusters or rosettes of siliques (Fig. 4 G) which may in part reflect the differential effect of the transgene on somatic versus reproductive organs. Sectored flowers similar to those shown in Fig. 4 D were also observed with the COOH-terminal GFP fusion (data not shown).


The cytokinesis gene KEULE encodes a Sec1 protein that binds the syntaxin KNOLLE.

Assaad FF, Huet Y, Mayer U, Jürgens G - J. Cell Biol. (2001)

KEULE is required for cytokinesis in somatic cells throughout the plant life cycle. (A) keule seedling, with its characteristic bloated surface. (B) Scanning electron micrograph of a keule seedling (hypocotyl), showing the bloated cells at the surface layer. (C) Wild-type flower. D–G are epimutations at the keule locus due most likely to cosuppression in transformants harboring a P35S::GFP-KEULE gene fusion. (D) Sectors are seen on petals and sepals, but not on the carpels or stamens. (E) Sector taking over the entire apical meristem. (F) Bloated, keule-like surface cells (arrows) in somatic sector boxed in D. (G) Lines with large numbers of mutant sectors (such as E) matured as a cluster or large rosette of fertile silliques. (H) Using an anti-GFP antibody, we fail to detect the GFP-KEULE fusion protein in cytokinesis-defective sectored plants (epimutant), but do see it in nonsectored siblings (normal). Anti-protein disulfide isomerase (PDI) was used as a loading control. Bar: (A) 300 μm; (B) 45 μm; (E) 200 μm; (F) 170 μm.
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Related In: Results  -  Collection

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Figure 4: KEULE is required for cytokinesis in somatic cells throughout the plant life cycle. (A) keule seedling, with its characteristic bloated surface. (B) Scanning electron micrograph of a keule seedling (hypocotyl), showing the bloated cells at the surface layer. (C) Wild-type flower. D–G are epimutations at the keule locus due most likely to cosuppression in transformants harboring a P35S::GFP-KEULE gene fusion. (D) Sectors are seen on petals and sepals, but not on the carpels or stamens. (E) Sector taking over the entire apical meristem. (F) Bloated, keule-like surface cells (arrows) in somatic sector boxed in D. (G) Lines with large numbers of mutant sectors (such as E) matured as a cluster or large rosette of fertile silliques. (H) Using an anti-GFP antibody, we fail to detect the GFP-KEULE fusion protein in cytokinesis-defective sectored plants (epimutant), but do see it in nonsectored siblings (normal). Anti-protein disulfide isomerase (PDI) was used as a loading control. Bar: (A) 300 μm; (B) 45 μm; (E) 200 μm; (F) 170 μm.
Mentions: GFP fusions (NH2- and COOH-terminal) of the KEULE full length sequence under the transcriptional control of the CaMV 35S promoter (a strong, fairly constitutive promoter) were introduced into wild-type Arabidopsis plants. The gene fusions failed to rescue the mutant phenotype (see Materials and Methods) and we therefore do not present the GFP fluorescence here as this was weakly and/or erroneously expressed and has unfortunately not enabled us to localize the KEULE protein. Interestingly, cytokinesis-defective mutant sectors (such as depicted in Fig. 4 D) appeared on a small fraction (∼6–7%, or 40 affected individuals in a population of ∼600 plants) of the wild-type transformants (with the NH2-terminal fusion). These were seen on all somatic organs of the plants including petals and sepals (Fig. 4D and Fig. F) as well as the apical meristem (Fig. 4 E) but not on the carpels, siliques, or stamens (Fig. 4 D). Cellular analysis of these sectors revealed the presence of large, bloated cells (Fig. 4 F, confocal analysis not shown) characteristic of keule mutants (Fig. 4A and Fig. B). Sectored plants exhibited striking clusters or rosettes of siliques (Fig. 4 G) which may in part reflect the differential effect of the transgene on somatic versus reproductive organs. Sectored flowers similar to those shown in Fig. 4 D were also observed with the COOH-terminal GFP fusion (data not shown).

Bottom Line: KEULE is characteristic of a Sec1 protein in that it appears to exist in two forms: soluble or peripherally associated with membranes.More importantly, KEULE binds the cytokinesis-specific syntaxin KNOLLE.Sec1 proteins are key regulators of vesicle trafficking, capable of integrating a large number of intra- and/or intercellular signals.

View Article: PubMed Central - PubMed

Affiliation: Genetics and Microbiology Institute, Ludwig Maximilians University, D-80638 Munich, Germany. fassaad@andrew2.stanford.edu

ABSTRACT
KEULE is required for cytokinesis in Arabidopsis thaliana. We have positionally cloned the KEULE gene and shown that it encodes a Sec1 protein. KEULE is expressed throughout the plant, yet appears enriched in dividing tissues. Cytokinesis-defective mutant sectors were observed in all somatic tissues upon transformation of wild-type plants with a KEULE-green fluorescent protein gene fusion, suggesting that KEULE is required not only during embryogenesis, but at all stages of the plant's life cycle. KEULE is characteristic of a Sec1 protein in that it appears to exist in two forms: soluble or peripherally associated with membranes. More importantly, KEULE binds the cytokinesis-specific syntaxin KNOLLE. Sec1 proteins are key regulators of vesicle trafficking, capable of integrating a large number of intra- and/or intercellular signals. As a cytokinesis-related Sec1 protein, KEULE appears to represent a novel link between cell cycle progression and the membrane fusion apparatus.

Show MeSH
Related in: MedlinePlus