Hitchhikers, highway tolls and roadworks : the interactions of plant viruses with the phloem

Work in J.T. lab is supported by the United Kingdom Biotechnology and Biological Sciences Research Council [grant number BB/M007200/1]. Some of the research discussed here was supported by grants from the National Science Foundation [grant numbers 1050883 and 1615723] to S.Y.F.The phloem is of central importance to plant viruses, providing the route by which they spread throughout their host. Compared with virus movement in non-vascular tissue, phloem entry, exit, and long-distance translocation usually involve additional viral factors and complex virus–host interactions, probably, because the phloem has evolved additional protection against these molecular ‘hitchhikers’. Recent progress in understanding phloem trafficking of endogenous mRNAs along with observations of membranous viral replication ‘factories’ in sieve elements challenge existing conceptions of virus long-distance transport. At the same time, the central role of the phloem in plant defences against viruses and the sophisticated viral manipulation of this host tissue are beginning to emerge.PostprintPeer reviewe