Plasmodesmata-Mediated Cell-to-Cell Communication in the Shoot Apical Meristem: How Stem Cells Talk.

Positional information is crucial for the determination of plant cell fates, and it is established based on coordinated cell-to-cell communication, which in turn is essential for plant growth and development. Plants have evolved a unique communication pathway, with tiny channels called plasmodesmata (PD) spanning the cell wall. PD interconnect most cells in the plant and generate a cytoplasmic continuum, to mediate short- and long-distance trafficking of various molecules. Cell-to-cell communication through PD plays a role in transmitting positional signals, however, the regulatory mechanisms of PD-mediated trafficking are still largely unknown. The induction and maintenance of stem cells in the shoot apical meristem (SAM) depends on PDmediated cell-to-cell communication, hence, it is an optimal model for dissecting the regulatory mechanisms of PD-mediated cell-to-cell communication and its function in specifying cell fates. In this review, we summarize recent knowledge of PD-mediated cell-to-cell communication in the SAM, and discuss mechanisms underlying molecular trafficking through PD and its role in plant development.