spacer gif spacer gif spacer gif spacer gif spacer gif
QUICK SEARCH:   [advanced]


spacer gif
     Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents    

First published online 10 June 2008
doi: 10.1242/jcs.027862

Journal of Cell Science 121, 2208-2216 (2008)
Published by The Company of Biologists 2008
This Article
Right arrow Summary Freely available
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Supplementary Material
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Related articles in JCS
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Riehs, N.
Right arrow Articles by Riha, K.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Riehs, N.
Right arrow Articles by Riha, K.
Social Bookmarking
Add to CiteULike   Add to Complore   Add to Connotea   Add to Del.icio.us   Add to Digg   Add to Reddit   Add to Technorati   Add to Twitter  
What's this?

Arabidopsis SMG7 protein is required for exit from meiosis

Nina Riehs1,*, Svetlana Akimcheva1,*, Jasna Puizina1,{ddagger}, Petra Bulankova1, Rachel A. Idol2,§, Jiri Siroky3, Alexander Schleiffer4, Dieter Schweizer1, Dorothy E. Shippen2 and Karel Riha1,¶

1 Gregor Mendel Institute of Molecular Plant Biology, Austrian Academy of Sciences, Dr Bohr-Gasse 3, 1030 Vienna, Austria
2 Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843-2128, USA
3 Institute of Biophysics, Czech Academy of Sciences, 612 65 Brno, Czech Republic
4 Research Institute of Molecular Pathology, 1030 Vienna, Austria


Figure 1
View larger version (83K):
[in this window]
[in a new window]

  		Fig. 1. Plants deficient for SMG7 exhibit growth defects and sterility. (A) Schematic representation of the Arabidopsis SMG7 gene with the indicated T-DNA insertions in the smg7-1, smg7-3 and smg7-5 alleles (see supplementary material Fig. S2 for the molecular structure of the insertions). White boxes represent exons. (B) Northern blot hybridization analysis showing the expression of the SMG7 gene in the indicated tissues. Full-length SMG7 cDNA was used as a probe. RNA loading was monitored by hybridization with a probe specific for the ACTIN2 (ACT2) gene. (C) Expression of the truncated transcripts from the SMG7 loci in smg7-1 and smg7-3 mutants. A molecular-weight marker is indicated. (D-H) Vegetative-growth phenotypes. (D) A silique from a plant heterozygous for the smg7-5 mutation with aborted seeds (indicated by arrowheads). (E) smg7-1 mutant plant 4 weeks after germination. Scale bar: 0.5 cm. (F) smg7-3 mutant plant germinated and grown for 4 weeks in soil. A control wild-type (wt) plant is indicated on the left. (G) 8-week-old smg7-1 mutant, which was grown for 3 weeks on agar before being transferred to soil. A 4-week-old wild-type plant is shown on the left. (H) Inflorescence bolts from wild-type and smg7-1 mutant plants. (I) Viable pollen grains in wild-type anthers have a dark-blue appearance after Alexander staining. Anthers of smg7 mutants are usually empty or contain only a few nonviable pollen-like structures that stain green. Scale bars: 0.1 mm.

 

Figure 2
View larger version (22K):
[in this window]
[in a new window]

  		Fig. 2. SMG7 deficiency increases the level of a PTC-containing transcript. (A) Alternative splicing of the At5g62760 gene produces a transcript containing a premature termination codon (+PTC) in the seventh exon (indicated by an asterisk) (Hori and Watanabe, 2005Go). (B) Detection of the At5g62760 transcripts by RT-PCR and Southern blot analysis. The quantity of the –PTC and +PTC transcripts was determined by quantitative RT-PCR analysis using primers T5-F and T5-R (see Materials and Methods; indicated in A). The relative quantity of the transcripts was determined by the signal ratio of +PTC to –PTC for each sample. The average ratios for +PTC to –PTC for wild-type and smg7-1 samples were 1.05±0.05 and 1.58±0.27, respectively.

 

Figure 3
View larger version (55K):
[in this window]
[in a new window]

  		Fig. 3. Aberrant meiosis in SMG7-deficient PMCs. (A-I) Meiosis in wild-type PMCs. (J-T) Meiosis in smg7-1 PMCs. (A,J) Pachytene, (B,K) metaphase I, (C,L) anaphase I, (D,M) telophase I, (E,N) metaphase II, (F,O) anaphase II. (G-I) Telophase II (G) in wild-type PMCs is followed by cytokinesis that results in the formation of tetrads (H) and microspores (I). (P,Q) smg7 mutants fail to decondense chromosomes during the second meiotic division, resulting in `irregular anaphase II' (P) and `scattered chromatids' (Q) meiocytes. (R-T) Decondensed chromosomes tend to cluster (R,S), forming polyads (T). (U-W) The distribution of chromosome 4 during late meiosis II was investigated by 3D-FISH with a chromosome-4-specific probe (green) in wild-type (U) and smg7-1 (V,W) plants. (U) Regular separation of chromosome 4 in A2. (V) Bilateral distribution of chromosome 4 during `irregular A2'. The broken line separates the products of the first meiotic division. (W) The clustering of chromosome 4 in the `scattered chromatids' meiocyte indicates random distribution of chromosomes at this stage. A-C and J-L were prepared by spreading PMCs fixed in ethanol:acetic acid (3:1; v/v) for better chromosome morphology. To preserve the 3D organization of the chromosomes in late meiotic PMCs (D-I, M-T and the 3D-FISH preparations U-W), cells were prepared from floral buds fixed in 4% paraformaldehyde. Scale bars: 5 µm.

 

Figure 4
View larger version (50K):
[in this window]
[in a new window]

  		Fig. 4. The meiotic cell cycle is significantly delayed at the anaphase-II–telophase-II transition in smg7 mutants. (A) Frequency of different stages of meiosis in developing floral buds. The total number of meiocytes is indicated below each pie chart. Nearly identical frequencies of prophase I stages in wild-type and smg7-1 0.1- to 0.3-mm buds demonstrate that progression of early meiosis correlates with flower development in smg7 mutants. (B) Deposited sporopollenin (green) on the surface of wild-type mononuclear microspore and smg7-1 polyad. DNA is counterstained with DAPI (red). Scale bars: 5 µm.

 

Figure 5
View larger version (73K):
[in this window]
[in a new window]

  		Fig. 5. Abnormal rearrangement of the spindle in late smg7 meiosis. (A-D) Meiosis II spindle in wild-type PMCs. (A) M2, (B) early A2, (C) late A2, (D) T2. (E-H) Meiosis II spindle in smg7-1 mutants (see Results for details).

 

Figure 6
View larger version (55K):
[in this window]
[in a new window]

  		Fig. 6. Centromeric cohesion in meiotic interphase and metaphase II in smg7-1 mutants. Centromeric DNA was analyzed by FISH with a 180-bp centromeric-repeat probe. (A-C) Representative examples of interkinesis; (D-F) M2. The centromeric probe was labeled with fluorescein (green) and DNA was counterstained with DAPI (red).

 

Figure 7
View larger version (40K):
[in this window]
[in a new window]

  		Fig. 7. MG115 treatment mimics the smg7 phenotype. A wild-type PMC treated with the proteasome inhibitor MG115 contains randomly dispersed separated chromatids (left panel). Irregular A2 detected in a non-treated smg7-1 mutant is shown at the right.

 

Add to CiteULike CiteULike   Add to Complore Complore   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us   Add to Digg Digg   Add to Reddit Reddit   Add to Technorati Technorati   Add to Twitter Twitter    What's this?



© The Company of Biologists Ltd 2008