Plasmodesmata: New perspectives on old questions

The progress so far and challenges remaining in developing a functional model of the macromolecular architecture of plasmodesmata are discussed. Details of the macromolecular components identified within plasmodesmata are summarised. Electron tomography and correlative microscopy techniques are explored as potential avenues to overcome the challenges in developing an accurate three-dimensional model of the macromolecular architecture of plasmodesmata. In recent years, some areas of plasmodesmatal biology have been left ignored, largely because the technologies required to advance them have been considered too difficult. For example, there have been no electrophysiological studies of plasmodesmata in the last decade and consequently no advances in our understanding of the rapid regulation of the permeability of plasmodesmata. There has also been no advance on the question of heterogeneity of function of the plasmodesmata within a wall and potential avenues to address this question are considered.