Plant paralog to viral movement protein that potentiates transport of mRNAinto the phloem

CmPP16 from Cucurbita maxima was cloned and the protein was shown to posses s 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 CmP P16 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 p ossesses the characteristics that are likely required to mediate RNA delive ry into the long-distance translocation stream. Thus, RNA may move within t he phloem as a component of a plant information superhighway.