Plant Paralog to Viral Movement Protein That Potentiates Transport of mRNA into the Phloem

TLDR

RNA can move within the phloem, forming a plant information superhighway. CmPP16, a Cucurbita maxima protein homologous to viral movement proteins, localizes to sieve elements, moves cell‑to‑cell, transports both sense and antisense RNA, and its mRNA is found in phloem, indicating it can mediate RNA delivery into long‑distance translocation.

Abstract

CmPP16 from Cucurbita maxima was cloned and the protein was shown to possess properties similar to those of viral movement proteins. CmPP16 messenger RNA (mRNA) is present in phloem tissue, whereas protein appears confined to sieve elements (SE). Microinjection and grafting studies revealed that CmPP16 moves from cell to cell, mediates the transport of sense and antisense RNA, and moves together with its mRNA into the SE of scion tissue. CmPP16 possesses the characteristics that are likely required to mediate RNA delivery into the long-distance translocation stream. Thus, RNA may move within the phloem as a component of a plant information superhighway.