Update on the Plant Nuclear Envelope and Nuclear Pore Dynamics of the Plant Nuclear Envelope and Nuclear Pore

The nucleus is the most prominent compartment of any eukaryotic cell and home to its genetic information. The nucleoplasm is surrounded by a double membrane system, the nuclear envelope (NE). The outer nuclear membrane (ONM) and the inner nuclear membrane (INM) are separated by the perinuclear space (or periplasmic space; Hetzer et al., 2005). The lipid bilayer of the ONM is continuous with the endoplasmic reticulum (ER), thus allowing for direct insertion of NE membrane proteins and translocation of proteins into the perinuclear space (Hetzer and Wente, 2009); however, the ONM protein composition differs from the ER (Hetzer et al., 2005). The INM has a distinct protein composition and specialized functions. The INM and ONM are fused at specific sites to form aqueous pores. Inserted at these sites are the nuclear pore complexes (NPCs), large protein conglomerates responsible for the selective nuclear import and export of macromolecules (D’Angelo and Hetzer, 2008; Brohawn et al., 2009). Chromatin association with the nuclear pores and the NE is involved in gene activation and repression, respectively (Akhtar and Gasser, 2007; Kalverda et al., 2008; Capelson and Hetzer, 2009). In higher organisms, the NE plays a role in the dissociation and reformation of the nucleus during cell division (Kutay and Hetzer, 2008). Proteins that interact in the perinuclear space connect the nucleoplasm and cytoplasm through the NE, thereby transmitting information from the cytoskeleton and giving rise to nuclear mobility (Burke and Roux, 2009). Like the ER, the NE lumen acts as a repository of calcium, and ion transporters in both the ONM and INM are involved in signal transduction (Erickson et al., 2006; Bootman et al., 2009). Together, the NE and NPCs are at the crossroad of communication between the nucleus and cytoplasm. Recent reviews have discussed the mechanism and relevance of nuclear import and export in plants (Merkle, 2009), the regulation of plant nuclear import in the context of signal transduction (Meier and Somers, 2011), and the plant NE during the cell cycle (Evans et al., 2011). Here, we focus on the dynamic organization of the NE and nuclear pore in quiescent and dividing plant cells. COMPONENTS OF THE NUCLEAR PERIPHERY