Structure and function of plasmodesmata

Little is known about the molecular architecture of plasmodesmata. Electron micrographs of plasmodesmata, although showing remarkably consistent featu res, do not reveal the dynamic nature of plasmodesmata. In addition, the ge nerally accepted size exclusion limit of plasmodesmata of 1 kDa as determin ed by the microinjection of fluorescent probes, is not an accurate measure of the size of molecules that can move from cell to cell. In some cases, pl asmodesmata allow the non-selective movement of proteins up to 50 kDa, wher eas others allow the selective transport of proteins such as transcription factors. Insights to the molecular architecture of plasmodesmata and the me chanism of cell-to-cell transport can be gained by the examination of the t ype of molecules and conditions under which selective and passive movement of molecules occurs.