Phloem-Mediated Long-Distance RNA Transport in Plants

In higher plants, the phloem acts not only as a conduit for photosynthates but also as a dynamic signalling highway for macromolecules such as RNAs. Messenger RNAs (mRNAs), small interfering RNAs and microRNAs can travel from source to sink organs, coordinating developmental programmes, stress responses and inter-organ communication. Within the phloem, living sieve tube elements are supported by companion cells, which selectively load RNAs into the translocation stream. Specific sequence motifs and secondary structures within RNAs are recognised by RNA-binding proteins (RBPs), forming ribonucleoprotein complexes that protect messages from nuclease degradation and facilitate movement. Upon arrival in distal tissues, RNAs may be released, translated or trigger gene-silencing cascades, thereby modulating target gene expression. Long-distance RNA transport underpins processes such as tuber formation, flowering time regulation and systemic immune responses. Grafting experiments have revealed bidirectional RNA exchange between scion and rootstock, offering opportunities to engineer novel traits without permanent genetic modification. Advances in high-throughput sequencing of phloem sap and refined proteomic analyses have begun to reveal the full complement of mobile transcripts and their carrier proteins, illuminating a sophisticated network of long-range information flow that enables plants to integrate environmental cues and developmental signals at the whole-plant level.

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Phloem-Mediated Long-Distance RNA Transport in Plants publication trend

The graph below shows the total number of articles in phloem-mediated long-distance rna transport in plants across all publications each year (not limited to Nature Index journals).

Technical terms

Phloem: The living tissue in vascular plants that conducts photosynthates and signalling molecules from source leaves to sink organs.

Sieve tube elements: Enucleate cells that form conduits in the phloem, permitting bulk flow of sap and macromolecules.

Companion cells: Parenchyma cells adjacent to sieve tubes that regulate phloem loading and support RNA transport.

Messenger RNA (mRNA): Single-stranded RNA molecules that carry genetic information for protein synthesis, some of which move long distances in plants.

RNA-binding protein (RBP): A protein that recognises and binds specific RNA motifs, forming complexes that facilitate RNA stability and transport.

Ribonucleoprotein (RNP) complex: A stable assembly of RNA and associated proteins that protects transcripts and mediates their intracellular or intercellular movement.

References

1. Genome-wide characterization of graft-transmissible mRNA-coding P450 genes of cucumber (Cucumis sativus L.). Horticultural Plant Journal (2023).
2. Messenger RNA exchange between scions and rootstocks in grafted grapevines. BMC Plant Biology (2015).
3. Phloem RNA-binding proteins as potential components of the long-distance RNA transport system. Frontiers in Plant Science (2013).
4. Analysis of the Pumpkin Phloem Proteome Provides Insights into Angiosperm Sieve Tube Function. Molecular & Cellular Proteomics (2008).
5. Elucidation of the Mechanisms of Long-Distance mRNA Movement in a Nicotiana benthamiana/Tomato Heterograft System. Plant Physiology (2018).
6. Polypyrimidine tract-binding proteins of potato mediate tuberization through an interaction with StBEL5 RNA. Journal of Experimental Botany (2015).