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Identification of Arabidopsis meiotic cyclins reveals functional diversification among plant cyclin genes.

Bulankova P, Akimcheva S, Fellner N, Riha K - PLoS Genet. (2013)

Bottom Line: We found six A-type cyclins and a single B-type cyclin (CYCB3;1) to be expressed in male meiosis.We further show that cyclin SDS does not contain a D-box and is constitutively expressed throughout meiosis.Our phenotypic and expression data provide extensive evidence that multiplication of cyclins is in plants accompanied by functional diversification.

View Article: PubMed Central - PubMed

Affiliation: Gregor Mendel Institute, Austrian Academy of Sciences, Vienna, Austria.

ABSTRACT
Meiosis is a modified cell division in which a single S-phase is followed by two rounds of chromosome segregation resulting in the production of haploid gametes. The meiotic mode of chromosome segregation requires extensive remodeling of the basic cell cycle machinery and employment of unique regulatory mechanisms. Cyclin-dependent kinases (CDKs) and cyclins represent an ancient molecular module that drives and regulates cell cycle progression. The cyclin gene family has undergone a massive expansion in angiosperm plants, but only a few cyclins were thoroughly characterized. In this study we performed a systematic immunolocalization screen to identify Arabidopsis thaliana A- and B-type cyclins expressed in meiosis. Many of these cyclins exhibit cell-type-specific expression in vegetative tissues and distinct subcellular localization. We found six A-type cyclins and a single B-type cyclin (CYCB3;1) to be expressed in male meiosis. Mutant analysis revealed that these cyclins contribute to distinct meiosis-related processes. While A2 cyclins are important for chromosome segregation, CYCB3;1 prevents ectopic cell wall formation. We further show that cyclin SDS does not contain a D-box and is constitutively expressed throughout meiosis. Analysis of plants carrying cyclin SDS with an introduced D-box motif determined that, in addition to its function in recombination, SDS acts together with CYCB3;1 in suppressing unscheduled cell wall synthesis. Our phenotypic and expression data provide extensive evidence that multiplication of cyclins is in plants accompanied by functional diversification.

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Ectopic cell wall-like structures in cycb3;1 mutants.(A–C) PMCs from cycb3;1 plants visualized by epifluorescence (left panel) and bright field (right panel) microscopy. DNA is counterstained with DAPI (white in A, red in B,C), microtubules (green in B,C) were detected with anti-α-tubulin antibody. (A) early anaphase I, (B) interkinesis, (C) metaphase II. Bars = 10 µm. (D,E) Section through anthers with PMCs in late meiosis I visualized by transmission scan electron microscopy. Arrows indicate ectopic cell wall-like structures, c – callose, Tp – tapetum cells. Bars represent 3 µm.
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pgen-1003508-g003: Ectopic cell wall-like structures in cycb3;1 mutants.(A–C) PMCs from cycb3;1 plants visualized by epifluorescence (left panel) and bright field (right panel) microscopy. DNA is counterstained with DAPI (white in A, red in B,C), microtubules (green in B,C) were detected with anti-α-tubulin antibody. (A) early anaphase I, (B) interkinesis, (C) metaphase II. Bars = 10 µm. (D,E) Section through anthers with PMCs in late meiosis I visualized by transmission scan electron microscopy. Arrows indicate ectopic cell wall-like structures, c – callose, Tp – tapetum cells. Bars represent 3 µm.

Mentions: CYCB3;1 is the only B-type cyclin detected in meiosis. This finding was surprising considering a prominent role of these cyclins in mitosis. To elucidate the function of CYCB3;1 in meiosis, we examined two mutant lines carrying T-DNA insertions disrupting the conserved C-terminal cyclin domains (cycb3;1-1 and cycb3;1-2 alleles; Figure S10). Plants with these alleles were fully fertile and did not exhibit any obvious growth defects. Nevertheless, we noticed that a fraction of PMCs harbored unusual structures that were apparent by bright field (BF) microscopy and resembled incomplete cell walls formed at ectopic locations (Figure 3, Figure S11). These cell wall-like structures were detected from prophase I through entire meiosis and in some extreme cases appeared to penetrate into chromatin or cut through a spindle (Figure 3B and Figure 4A). Transmission electron microscopy (TEM) revealed unusual cell wall invaginations into the cell interior (Figure 3E) which corroborated bright field microscopy data. These observations indicate that CYCB3;1 activity contributes to spatial and temporal regulation of cell wall formation in PMCs.


Identification of Arabidopsis meiotic cyclins reveals functional diversification among plant cyclin genes.

Bulankova P, Akimcheva S, Fellner N, Riha K - PLoS Genet. (2013)

Ectopic cell wall-like structures in cycb3;1 mutants.(A–C) PMCs from cycb3;1 plants visualized by epifluorescence (left panel) and bright field (right panel) microscopy. DNA is counterstained with DAPI (white in A, red in B,C), microtubules (green in B,C) were detected with anti-α-tubulin antibody. (A) early anaphase I, (B) interkinesis, (C) metaphase II. Bars = 10 µm. (D,E) Section through anthers with PMCs in late meiosis I visualized by transmission scan electron microscopy. Arrows indicate ectopic cell wall-like structures, c – callose, Tp – tapetum cells. Bars represent 3 µm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3649987&req=5

pgen-1003508-g003: Ectopic cell wall-like structures in cycb3;1 mutants.(A–C) PMCs from cycb3;1 plants visualized by epifluorescence (left panel) and bright field (right panel) microscopy. DNA is counterstained with DAPI (white in A, red in B,C), microtubules (green in B,C) were detected with anti-α-tubulin antibody. (A) early anaphase I, (B) interkinesis, (C) metaphase II. Bars = 10 µm. (D,E) Section through anthers with PMCs in late meiosis I visualized by transmission scan electron microscopy. Arrows indicate ectopic cell wall-like structures, c – callose, Tp – tapetum cells. Bars represent 3 µm.
Mentions: CYCB3;1 is the only B-type cyclin detected in meiosis. This finding was surprising considering a prominent role of these cyclins in mitosis. To elucidate the function of CYCB3;1 in meiosis, we examined two mutant lines carrying T-DNA insertions disrupting the conserved C-terminal cyclin domains (cycb3;1-1 and cycb3;1-2 alleles; Figure S10). Plants with these alleles were fully fertile and did not exhibit any obvious growth defects. Nevertheless, we noticed that a fraction of PMCs harbored unusual structures that were apparent by bright field (BF) microscopy and resembled incomplete cell walls formed at ectopic locations (Figure 3, Figure S11). These cell wall-like structures were detected from prophase I through entire meiosis and in some extreme cases appeared to penetrate into chromatin or cut through a spindle (Figure 3B and Figure 4A). Transmission electron microscopy (TEM) revealed unusual cell wall invaginations into the cell interior (Figure 3E) which corroborated bright field microscopy data. These observations indicate that CYCB3;1 activity contributes to spatial and temporal regulation of cell wall formation in PMCs.

Bottom Line: We found six A-type cyclins and a single B-type cyclin (CYCB3;1) to be expressed in male meiosis.We further show that cyclin SDS does not contain a D-box and is constitutively expressed throughout meiosis.Our phenotypic and expression data provide extensive evidence that multiplication of cyclins is in plants accompanied by functional diversification.

View Article: PubMed Central - PubMed

Affiliation: Gregor Mendel Institute, Austrian Academy of Sciences, Vienna, Austria.

ABSTRACT
Meiosis is a modified cell division in which a single S-phase is followed by two rounds of chromosome segregation resulting in the production of haploid gametes. The meiotic mode of chromosome segregation requires extensive remodeling of the basic cell cycle machinery and employment of unique regulatory mechanisms. Cyclin-dependent kinases (CDKs) and cyclins represent an ancient molecular module that drives and regulates cell cycle progression. The cyclin gene family has undergone a massive expansion in angiosperm plants, but only a few cyclins were thoroughly characterized. In this study we performed a systematic immunolocalization screen to identify Arabidopsis thaliana A- and B-type cyclins expressed in meiosis. Many of these cyclins exhibit cell-type-specific expression in vegetative tissues and distinct subcellular localization. We found six A-type cyclins and a single B-type cyclin (CYCB3;1) to be expressed in male meiosis. Mutant analysis revealed that these cyclins contribute to distinct meiosis-related processes. While A2 cyclins are important for chromosome segregation, CYCB3;1 prevents ectopic cell wall formation. We further show that cyclin SDS does not contain a D-box and is constitutively expressed throughout meiosis. Analysis of plants carrying cyclin SDS with an introduced D-box motif determined that, in addition to its function in recombination, SDS acts together with CYCB3;1 in suppressing unscheduled cell wall synthesis. Our phenotypic and expression data provide extensive evidence that multiplication of cyclins is in plants accompanied by functional diversification.

Show MeSH
Related in: MedlinePlus