Transport of macromolecules through the phloemhas received increasing interest since thediscovery thatFLOWERINGLOCUST(FT) moves from leaves to the shoot apical meristem, where it induces flowering (Corbesier et al., 2007), indicating thatmacromolecules such as proteins andRNAcan act asmobile regulators of gene expression in distant tissues. Indeed,Molnaretal. (2010)usedgrafting between Arabidop...