Structural organization of the plant nucleus: Nuclear envelope, pore complexes and nucleoskeleton

Abstract

Plants, like all other eukaryotes, contain their genome within the nuclear compartment. The purpose of this compartment is to separate the transcriptional machinery from the sites of protein synthesis. There is therefore an impermeable barrier between the nuclear and cytoplasmic compartments, the nuclear envelope (NE). However the NE is permeated with large protein channels, the nuclear pore complexes (NPCs). Trafficking through the NPCs can therefore be used to control gene expression at several levels. The outer and inner membranes both contain distinct and complex sets of proteins, which link to the cytoskeleton as well as the nuclear interior. The nucleus also therefore has important functions in organising both the genome and the cytoplasm. Here we describe the architecture and dynamics of the structural components of the nucleus and discuss how the plant nucleus appears to differ in important ways from animals and fungi, while maintaining many similarities. First we will focus on the NE of plants and their specific protein composition, structure and function compared to animal systems. We will then discuss the role of the NE as a barrier and interface between the cytoplasm and nucleoplasm, before focussing on communication across the NE and finally discussing how the nuclear interior is structurally organised by the nucleoskeleton. Although the proteins and functions of the NE and nucleoskeleton appear to overlap, we discuss them separately so as not to confuse the distinct functions that do clearly exist.