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IN BRIEF

The Nuclear Pore Complex in Arabidopsis
Getting molecules in and out of the nucleus
is a critical function of eukaryotic cells. Thetask is performed by the nuclear porecomplex (NPC), a massive protein complex(estimated at 125 MD in vertebrates) thatspans the nuclear envelope and allows
diffusion of small molecules but tightly
controls transport of larger molecules,
such as proteins, RNA, and ribosomal
subunits. The NPC comprises at least 30
different proteins, called nucleoporins.
Knowledge of the functions of individualcomponents and the overall structure inplants lags behind that of vertebrates andyeast, for which the NPC is well characterized (recently reviewed in Wälde andKehlenbach, 2010). Tamura et al. (pagesnnn) present a detailed investigation ofcomponents of the NPC in Arabidopsis
based on an interactive proteomic ap-

proach using green fluorescent protein(GFP)-tagged nucleoporins.
The authors started with a known plant
nucleoporin, RNA export factor 1 (RAE1),
which is encoded by numerous plant genomes. Transgenic Arabidopsis plants
expressing GFP-tagged At-RAE1 were generated and used to analyze the NPC inliving cells and to identify other nucleoporins that make up the NPC in Arabidopsis.
Nucleoporins were identified by immunoprecipation from transgenic Arabidopsis
tissue using anti-GFP antibody followedby mass spectrometry identification ofproteins present in the immunoprecipitate.
Using this approach, eight known plant
nucleoporins and 22 novel nucleoporins
were isolated and further characterized bycloning and localization of GFP-nucleoporin
fusion proteins.

Most of the Arabidopsis nucleoporins
show homology to human nucleoporins, except for one protein, called Nup136/Nup1,
which was found to be plant specific.
Database searches revealed Nup136/Nup1
homologs in a number of plant species but
not in yeast or vertebrates. T-DNA insertional mutants of nup136/nup1 showed
defects in flowering time and pollen development (see figure), suggesting that Nup136
plays a role in aspects of flowering andreproductive development in plants. Structural features of Nup136/Nup1 indicate thatthe protein might be involved in regulating
active transport through the NPC.
Overall, the Arabidopsis nucleoporins
identified shared higher homology withvertebrate than with yeast nucleoporins,
suggesting that the plant NPC structure ismore similar to that of vertebrates thanyeast. This work shows that the basic NPC
structure is conserved in plants, yeast, andvertebrates, although each organism uses
specialized nucleoporins with functions
specific to their own NPCs. The identification of 22 novel plant nucleoporins will
facilitate further studies into their interactions, regulatory roles, and biological functions within the NPC.

Nancy A. Eckardt
Senior Features Editor
neckardt@aspb.org

REFERENCES

Mutants of nup136 exhibit defects in plant development. Top panel: nup136 knockout mutants
showed a defect in fruit maturation. Inset shows a magnified view of representative siliques. Bottom
panel: Scanning electron micrographs of pollen grains of wild-type (wt) and nup136 mutant plants.
Arrows indicate the shrunken pollen grains of the mutants. Bar ¼ 50 mm. (Figure reproduced fromTamura et al. [2010].)

Tamura, K., Fukao, Y., Iwamoto, M., Haraguchi,T., and Hara-Nishimura, I. (2010). Identification and characterization of nuclear pore complex components in Arabidopsis thaliana. Plant
Cell 22: nnn.
Wälde, S., and Kehlenbach, R.H. (2010). The
part and the whole: Functions of nucleoporins
in nucleocytoplasmic transport. Trends CellBiol. 20: 461-469.

www.plantcell.org/cgi/doi/10.1105/tpc.110.221211

The Plant Cell Preview, www.aspb.org ã 2010 American Society of Plant Biologists

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The Nuclear Pore Complex in Arabidopsis
Nancy A. Eckardt
Plant Cell; originally published online December 23, 2010;
DOI 10.1105/tpc.110.221211
This information is current as of September 16, 2011
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