Plasmodesmata "in Communicado"

Abstract

Cell-to-cell communication is fundamental to multicellular life. For this to occur effectively there must be pathways and dynamic networks for communication. These might depend upon electrical or chemical signals or the mass transfer of molecules between adjacent cells. Molecular communication occurs either via an extra-cellular pathway or through physical structures, called plasmodesmata, that connect the cytoplasm of neighboring cells. Plasmodesmata bridge the rigid physical barrier presented by the cell wall to extend the symplasm from single cells to tissue domains that have functional importance for tissue growth, development, and defense. Although recent years have seen advances in our knowledge of the physical nature of PD, the trafficked molecules, and of the wider processes they affect, our knowledge of PD structure and function is still relatively rudimentary. This article will consider the technical/experimental difficulties hindering PD research and suggest priorities in the future research effort that might advance the field at a significantly faster rate.

Keywords: callose; cell-to-cell communication; molecular flux; plasmodesmata.

Figure 1

Plant growth and development depends upon cellular communication over short and long distances. This communication depends in part upon movement of molecules via the symplasm – the cytoplasmic continuum that is connected through cell walls by plasmodesmata. Through plasmodesmata cytoplasm, plasma membrane and endoplasmic reticulum are all continuous, providing paths for molecular flux.

Figure 2

Plasmodesmal aperture is regulated by callose deposition in the cell wall surrounding the neck of the pore. Plasmodesmata-located callose synthases and β-1,3-glucanases control callose turnover which dictates whether a plasmodesma is open (left) or closed (right) and whether movement can occur freely between cells (left) or is obstructed (right).