Formation of plasmodesmata bridges through ER-dependent incomplete cytokinesis

Plasmodesmata are important for intercellular communication in plants. They are formed through incomplete cytokinesis during which there is no “final cut” of the communication between daughter cells. Unlike animal cells that have a single bridge between cells, plants create several hundreds of plasmodesmata bridges between daughter cells. While the function and structure of the plasmodesmata has been known for many years, the formation process of the plasmodesmata has been a mystery and this is what Li et al. seek to uncover. Using the model plant Arabidopsis thaliana, the authors used high-resolution imaging techniques to map the transition from cell plate formation to the formation of the plasmodesmata. They showed that the endoplasmic reticulum (ER) serves as the “architect”, as it moves through fenestrae (holes) in the cell plate. As the cell plate matures to become the plasmodesmata, fenestrae (holes) without the ER are shut off, while those with ER cell-cell continuity eventually become the nascent plasmodesmata, leading to bridge formation, hence, communication between cells. As with any literal bridge construction, the ER-PM protein tethers  MCTP3, MCTP4 and MCTP6 act as the “construction workers” needed to stabilize this bridge between cells. (Summary by Nathaniel Oragbon @NathanIgwe) Science  10.1126/science.adn4630