Signaling-dependent cytoskeletal dynamics and plant cell growth

In all eukaryotic cells, the cytoskeleton is an essential protein-based matrix that determines the cell’s internal order. Building a cell requires necessarily an organizational support able to provide the order and thus to regulate the various cellular functions. Classically, the cytoskeleton comprises a heterogeneous group of proteins that interact with each other to form a dynamic network that adapts to the different physiological conditions of cells. The cytoskeleton receives information as decoded by the signal transduction system and conveys them in a response that might include the moving of specific cellular components, cell division or changes in cell shape. In plant cells, the appearance of the cell wall has dictated some limitations not found in animal cells and has affected the structure of the cytoskeleton by modifying both organization and composition of cytoskeleton proteins. The cytoskeleton also takes active part in the construction of the cell wall; because the cell wall defines the shape of a plant cell, it follows that the cytoskeleton actively participates in the shaping process. Although the cell wall is a semi-rigid structure that severely limits cell motility, the cytoskeleton is not static but is a finely-tuned highly dynamic matrix that reorganizes in response to external cues. The differences that evolved in the plant cell cytoskeleton can be macroscopic (for example, the disappearance of intermediate filaments) or more difficult to appreciate (i.e. the substitution of a few amino acids in highly conserved proteins). Although the presence of the cell wall has imposed some restrictions to both cell motility and shaping, it did not affect specific molecular repertoire or processes, e.g. neither the number of genes coding for cytoskeletal proteins nor the number of isoforms or post-translational modifications to which cytoskeletal proteins are subjected