Traveling with purpose: cell-to-cell transport of plant mRNAs

mRNAs traffic between plant cells/tissues/organs via plasmodesmata (PDs) and the phloem to act as noncell-autonomous signals controlling diverse biological processes.Some RNA features and RNA-binding proteins important for long-distance mRNA phloem transport have been identified.Transcription factor mRNAs and proteins selectively traffic from cell-to-cell via PDs to regulate cell fates and tissue patterning. Although their transport mechanisms are less well understood, integration of the available information allows the prediction of possible mechanisms.The endomembrane system, cytoskeleton, motor proteins, RNA helicases, and RNA-processing proteins all participate in the cell-to-cell transport of mRNAs.Cell-to-cell transport of mRNAs contributes to the propagation of mobile transcription factor signals. Messenger RNAs (mRNAs) in multicellular organisms can act as signals transported cell-to-cell and over long distances. In plants, mRNAs traffic cell-to-cell via plasmodesmata (PDs) and over long distances via the phloem vascular system to control diverse biological processes – such as cell fate and tissue patterning – in destination organs. Research on long-distance transport of mRNAs in plants has made remarkable progress, including the cataloguing of many mobile mRNAs, characterization of mRNA features important for transport, identification of mRNA-binding proteins involved in their transport, and understanding of the physiological roles of mRNA transport. However, information on short-range mRNA cell-to-cell transport is still limited. This review discusses the regulatory mechanisms and physiological functions of mRNA transport at the cellular and whole plant levels.