Involvement of the cytoskeleton in the secretory pathway and plasma membrane organisation of higher plant cells

摘要

In eukaryotic cells, morphogenetic processes are highly dependent of the cell's ability to provide the right molecules at the right time and to place them in the right place. The genesis and dynamics of a complex endomembrane system, which is organised in discrete compartments contribute to this orchestration of cell functioning. A common functional organisation seems to dictate the continuous exchange of cargo molecules between the endomembrane compartments. Biochemical and cytological studies have long established that a functional hierarchy exists between these compartments: proteins enter the secretory/exocytic pathway by being inserted in the endoplasmic reticulum (ER), they are then transported to the Golgi apparatus (GA) where they are further processed (in glycosylation for instance), and sent to either the lysosomes/vacuoles (V), or to the plasma membrane. Retrograde transport through endocytic pathways has also been described (see [Murphy et al., 2005], [Nergaard-Johansen et al., 2006] and [Samaj et al., 2005] for reviews). The era of genomics has recently allowed important progression in the understanding of the molecular machineries involved in this routage of cargo molecules between these compartments. The question of the exact mechanisms involved in the cellular and ultrastructural organisation of the endomembrane system remains open. It is conceivable that flexible, yet highly regulated processes must occur, as the morphology and dynamics of the endomembrane system may vary from one cell to another depending on the tissue, the physiological state, or even the nature of the products secreted (Kepes et al., 2005).