Nuclear envelope and nuclear pore complex structure and organization in tobacco BY‐2 cells

Abstract

SUMMARYThe nuclear envelope (NE) is a fundamental structure of eukaryotic cells with a dual role: it separates two distinct compartments, and enables communication between them via nuclear pore complexes (NPCs). Little is known about NPCs and NE structural organization in plants. We investigated the structure of NPCs from both sides of the NE in tobacco BY-2 cells. We detected structural differences between the NPCs of dividing and quiescent nuclei. Importantly, we also traced the organizational pattern of the NPCs, and observed nonrandom NPC distribution over the nuclear surface. Lastly, we observed an organized filamentous protein structure that underlies the inner nuclear membrane, and interconnects NPCs. The results are discussed within the context of the current understanding of NE structure and function in higher eukaryotes.

Dynamics of the Plant Nuclear Envelope and Nuclear Pore

“…An in-depth view of the tobacco BY-2 cell and onion (Allium cepa) NPC structure and organization has recently been provided, demonstrating that the plant NPC closely resembles the known yeast and vertebrate NPCs (Fiserova et al, 2009). Plant NPCs appear to be surprisingly densely spaced (approximately 50 NPCs mm 22 compared with 60 NPCs mm 22 for Xenopus laevis oocytes, considered very rich in NPCs).…”

“…A meshwork of filaments underlying the inner NE in tobacco (Nicotiana tabacum) BY-2 cells was recently revealed, closely resembling the animal nuclear lamina both in terms of organization and filament thickness (Fiserova et al, 2009). The best candidates for plant lamin-like proteins are currently a family of coiled-coil proteins about twice the size of lamins but with similar overall structure.…”

The nuclear pore complex: structure and function

“…Closer analyses of the central spoke ring revealed a similar thickness (~ 35 nm) of this ring in different species, indicating that the size differences within the central framework arise from species-specific variations in the arrangements of the cytoplasmic and nuclear rings (Frenkiel-Krispin et al, 2010). Despite these differences in the dimensions of the central framework, the diameter of the central pore in the mid plane of the NE is about 40 and 50 nm (Fahrenkrog et al, 1998;Yang et al, 1998;Stoffler et al, 2003;Beck et al, 2007, Fiserova et al, 2009Frenkiel-Krispin et al, 2010;Bui et al, 2013), which is close to the size limit of 39 nm in diameter for cargo translocation (Panté and Kann, 2002). Besides the central pore, metazoan NPCs exhibit peripheral channels of ~ 5-10 nm in diameter (Hinshaw et al, 1992;Akey and Radermacher, 1993;Yang et al, 1998;Stoffler et al, 2003;Beck et al, 2007;Maimon et al, 2013).…”

Nuclear pore complex tethers to the cytoskeleton

“…1), a complex intermediate filament network that lines the inner nuclear membrane. How, and whether, NPCs are anchored in plants (Fiserova et al, 2009) and other organisms is not so clear. The nuclear lamina, amongst other roles, is a major component of a mechanically robust inner shell for the NE (Schäpe et al, 2009).…”