Transcription factors on the move.

We think of transcription factors as being confined to the cell where they are transcribed, but recent work shows they are able to move from cell to cell in plants. Plant cells are thought to communicate through membrane-lined channels called plasmodesmata. Although the size exclusion limit for these pores is small, microinjection experiments indicate that macromolecular trafficking through plasmodesmata occurs and can be regulated. But can functional plant proteins in their normal expression domain also move between cells? A recent paper by Sessions et al. elegantly addresses this question using meristem chimeras. Intriguingly, only one of the two proteins studied moved, thereby setting the stage for analysis of the mechanism and selectivity of protein trafficking between cells.